51 skills found · Page 1 of 2
prakharsr / Audiobook CreatorAudiobook Creator is an app that converts books (EPUB, PDF, TXT etc.) into fully voiced audiobooks with intelligent character voice attribution. It uses LLMs and Kokoro/Orpheus TTS to generate engaging, multi-voice audiobooks. Features include emotion tag addition, character identification, and customizable narration. Licensed under GPL-3.0
johnuberbacher / Invoice GeneratorAn Invoice creator project built with React. Uses jspdf-react to capture the data from the modal and convert it from canvas -> pdf.
hajareshyam / Pdf Creator NodeThis package is used to generate HTML to PDF in Nodejs
ManojKumarPatnaik / Major Project ListA list of practical projects that anyone can solve in any programming language (See solutions). These projects are divided into multiple categories, and each category has its own folder. To get started, simply fork this repo. CONTRIBUTING See ways of contributing to this repo. You can contribute solutions (will be published in this repo) to existing problems, add new projects, or remove existing ones. Make sure you follow all instructions properly. Solutions You can find implementations of these projects in many other languages by other users in this repo. Credits Problems are motivated by the ones shared at: Martyr2’s Mega Project List Rosetta Code Table of Contents Numbers Classic Algorithms Graph Data Structures Text Networking Classes Threading Web Files Databases Graphics and Multimedia Security Numbers Find PI to the Nth Digit - Enter a number and have the program generate PI up to that many decimal places. Keep a limit to how far the program will go. Find e to the Nth Digit - Just like the previous problem, but with e instead of PI. Enter a number and have the program generate e up to that many decimal places. Keep a limit to how far the program will go. Fibonacci Sequence - Enter a number and have the program generate the Fibonacci sequence to that number or to the Nth number. Prime Factorization - Have the user enter a number and find all Prime Factors (if there are any) and display them. Next Prime Number - Have the program find prime numbers until the user chooses to stop asking for the next one. Find Cost of Tile to Cover W x H Floor - Calculate the total cost of the tile it would take to cover a floor plan of width and height, using a cost entered by the user. Mortgage Calculator - Calculate the monthly payments of a fixed-term mortgage over given Nth terms at a given interest rate. Also, figure out how long it will take the user to pay back the loan. For added complexity, add an option for users to select the compounding interval (Monthly, Weekly, Daily, Continually). Change Return Program - The user enters a cost and then the amount of money given. The program will figure out the change and the number of quarters, dimes, nickels, pennies needed for the change. Binary to Decimal and Back Converter - Develop a converter to convert a decimal number to binary or a binary number to its decimal equivalent. Calculator - A simple calculator to do basic operators. Make it a scientific calculator for added complexity. Unit Converter (temp, currency, volume, mass, and more) - Converts various units between one another. The user enters the type of unit being entered, the type of unit they want to convert to, and then the value. The program will then make the conversion. Alarm Clock - A simple clock where it plays a sound after X number of minutes/seconds or at a particular time. Distance Between Two Cities - Calculates the distance between two cities and allows the user to specify a unit of distance. This program may require finding coordinates for the cities like latitude and longitude. Credit Card Validator - Takes in a credit card number from a common credit card vendor (Visa, MasterCard, American Express, Discoverer) and validates it to make sure that it is a valid number (look into how credit cards use a checksum). Tax Calculator - Asks the user to enter a cost and either a country or state tax. It then returns the tax plus the total cost with tax. Factorial Finder - The Factorial of a positive integer, n, is defined as the product of the sequence n, n-1, n-2, ...1, and the factorial of zero, 0, is defined as being 1. Solve this using both loops and recursion. Complex Number Algebra - Show addition, multiplication, negation, and inversion of complex numbers in separate functions. (Subtraction and division operations can be made with pairs of these operations.) Print the results for each operation tested. Happy Numbers - A happy number is defined by the following process. Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers, while those that do not end in 1 are unhappy numbers. Display an example of your output here. Find the first 8 happy numbers. Number Names - Show how to spell out a number in English. You can use a preexisting implementation or roll your own, but you should support inputs up to at least one million (or the maximum value of your language's default bounded integer type if that's less). Optional: Support for inputs other than positive integers (like zero, negative integers, and floating-point numbers). Coin Flip Simulation - Write some code that simulates flipping a single coin however many times the user decides. The code should record the outcomes and count the number of tails and heads. Limit Calculator - Ask the user to enter f(x) and the limit value, then return the value of the limit statement Optional: Make the calculator capable of supporting infinite limits. Fast Exponentiation - Ask the user to enter 2 integers a and b and output a^b (i.e. pow(a,b)) in O(LG n) time complexity. Classic Algorithms Collatz Conjecture - Start with a number n > 1. Find the number of steps it takes to reach one using the following process: If n is even, divide it by 2. If n is odd, multiply it by 3 and add 1. Sorting - Implement two types of sorting algorithms: Merge sort and bubble sort. Closest pair problem - The closest pair of points problem or closest pair problem is a problem of computational geometry: given n points in metric space, find a pair of points with the smallest distance between them. Sieve of Eratosthenes - The sieve of Eratosthenes is one of the most efficient ways to find all of the smaller primes (below 10 million or so). Graph Graph from links - Create a program that will create a graph or network from a series of links. Eulerian Path - Create a program that will take as an input a graph and output either an Eulerian path or an Eulerian cycle, or state that it is not possible. An Eulerian path starts at one node and traverses every edge of a graph through every node and finishes at another node. An Eulerian cycle is an eulerian Path that starts and finishes at the same node. Connected Graph - Create a program that takes a graph as an input and outputs whether every node is connected or not. Dijkstra’s Algorithm - Create a program that finds the shortest path through a graph using its edges. Minimum Spanning Tree - Create a program that takes a connected, undirected graph with weights and outputs the minimum spanning tree of the graph i.e., a subgraph that is a tree, contains all the vertices, and the sum of its weights is the least possible. Data Structures Inverted index - An Inverted Index is a data structure used to create full-text search. Given a set of text files, implement a program to create an inverted index. Also, create a user interface to do a search using that inverted index which returns a list of files that contain the query term/terms. The search index can be in memory. Text Fizz Buzz - Write a program that prints the numbers from 1 to 100. But for multiples of three print “Fizz” instead of the number and for the multiples of five print “Buzz”. For numbers which are multiples of both three and five print “FizzBuzz”. Reverse a String - Enter a string and the program will reverse it and print it out. Pig Latin - Pig Latin is a game of alterations played in the English language game. To create the Pig Latin form of an English word the initial consonant sound is transposed to the end of the word and an ay is affixed (Ex.: "banana" would yield anana-bay). Read Wikipedia for more information on rules. Count Vowels - Enter a string and the program counts the number of vowels in the text. For added complexity have it report a sum of each vowel found. Check if Palindrome - Checks if the string entered by the user is a palindrome. That is that it reads the same forwards as backward like “racecar” Count Words in a String - Counts the number of individual words in a string. For added complexity read these strings in from a text file and generate a summary. Text Editor - Notepad-style application that can open, edit, and save text documents. Optional: Add syntax highlighting and other features. RSS Feed Creator - Given a link to RSS/Atom Feed, get all posts and display them. Quote Tracker (market symbols etc) - A program that can go out and check the current value of stocks for a list of symbols entered by the user. The user can set how often the stocks are checked. For CLI, show whether the stock has moved up or down. Optional: If GUI, the program can show green up and red down arrows to show which direction the stock value has moved. Guestbook / Journal - A simple application that allows people to add comments or write journal entries. It can allow comments or not and timestamps for all entries. Could also be made into a shoutbox. Optional: Deploy it on Google App Engine or Heroku or any other PaaS (if possible, of course). Vigenere / Vernam / Ceasar Ciphers - Functions for encrypting and decrypting data messages. Then send them to a friend. Regex Query Tool - A tool that allows the user to enter a text string and then in a separate control enter a regex pattern. It will run the regular expression against the source text and return any matches or flag errors in the regular expression. Networking FTP Program - A file transfer program that can transfer files back and forth from a remote web sever. Bandwidth Monitor - A small utility program that tracks how much data you have uploaded and downloaded from the net during the course of your current online session. See if you can find out what periods of the day you use more and less and generate a report or graph that shows it. Port Scanner - Enter an IP address and a port range where the program will then attempt to find open ports on the given computer by connecting to each of them. On any successful connections mark the port as open. Mail Checker (POP3 / IMAP) - The user enters various account information include web server and IP, protocol type (POP3 or IMAP), and the application will check for email at a given interval. Country from IP Lookup - Enter an IP address and find the country that IP is registered in. Optional: Find the Ip automatically. Whois Search Tool - Enter an IP or host address and have it look it up through whois and return the results to you. Site Checker with Time Scheduling - An application that attempts to connect to a website or server every so many minute or a given time and check if it is up. If it is down, it will notify you by email or by posting a notice on the screen. Classes Product Inventory Project - Create an application that manages an inventory of products. Create a product class that has a price, id, and quantity on hand. Then create an inventory class that keeps track of various products and can sum up the inventory value. Airline / Hotel Reservation System - Create a reservation system that books airline seats or hotel rooms. It charges various rates for particular sections of the plane or hotel. For example, first class is going to cost more than a coach. Hotel rooms have penthouse suites which cost more. Keep track of when rooms will be available and can be scheduled. Company Manager - Create a hierarchy of classes - abstract class Employee and subclasses HourlyEmployee, SalariedEmployee, Manager, and Executive. Everyone's pay is calculated differently, research a bit about it. After you've established an employee hierarchy, create a Company class that allows you to manage the employees. You should be able to hire, fire, and raise employees. Bank Account Manager - Create a class called Account which will be an abstract class for three other classes called CheckingAccount, SavingsAccount, and BusinessAccount. Manage credits and debits from these accounts through an ATM-style program. Patient / Doctor Scheduler - Create a patient class and a doctor class. Have a doctor that can handle multiple patients and set up a scheduling program where a doctor can only handle 16 patients during an 8 hr workday. Recipe Creator and Manager - Create a recipe class with ingredients and put them in a recipe manager program that organizes them into categories like desserts, main courses, or by ingredients like chicken, beef, soups, pies, etc. Image Gallery - Create an image abstract class and then a class that inherits from it for each image type. Put them in a program that displays them in a gallery-style format for viewing. Shape Area and Perimeter Classes - Create an abstract class called Shape and then inherit from it other shapes like diamond, rectangle, circle, triangle, etc. Then have each class override the area and perimeter functionality to handle each shape type. Flower Shop Ordering To Go - Create a flower shop application that deals in flower objects and use those flower objects in a bouquet object which can then be sold. Keep track of the number of objects and when you may need to order more. Family Tree Creator - Create a class called Person which will have a name, when they were born, and when (and if) they died. Allow the user to create these Person classes and put them into a family tree structure. Print out the tree to the screen. Threading Create A Progress Bar for Downloads - Create a progress bar for applications that can keep track of a download in progress. The progress bar will be on a separate thread and will communicate with the main thread using delegates. Bulk Thumbnail Creator - Picture processing can take a bit of time for some transformations. Especially if the image is large. Create an image program that can take hundreds of images and converts them to a specified size in the background thread while you do other things. For added complexity, have one thread handling re-sizing, have another bulk renaming of thumbnails, etc. Web Page Scraper - Create an application that connects to a site and pulls out all links, or images, and saves them to a list. Optional: Organize the indexed content and don’t allow duplicates. Have it put the results into an easily searchable index file. Online White Board - Create an application that allows you to draw pictures, write notes and use various colors to flesh out ideas for projects. Optional: Add a feature to invite friends to collaborate on a whiteboard online. Get Atomic Time from Internet Clock - This program will get the true atomic time from an atomic time clock on the Internet. Use any one of the atomic clocks returned by a simple Google search. Fetch Current Weather - Get the current weather for a given zip/postal code. Optional: Try locating the user automatically. Scheduled Auto Login and Action - Make an application that logs into a given site on a schedule and invokes a certain action and then logs out. This can be useful for checking webmail, posting regular content, or getting info for other applications and saving it to your computer. E-Card Generator - Make a site that allows people to generate their own little e-cards and send them to other people. Do not use Flash. Use a picture library and perhaps insightful mottos or quotes. Content Management System - Create a content management system (CMS) like Joomla, Drupal, PHP Nuke, etc. Start small. Optional: Allow for the addition of modules/addons. Web Board (Forum) - Create a forum for you and your buddies to post, administer and share thoughts and ideas. CAPTCHA Maker - Ever see those images with letters numbers when you signup for a service and then ask you to enter what you see? It keeps web bots from automatically signing up and spamming. Try creating one yourself for online forms. Files Quiz Maker - Make an application that takes various questions from a file, picked randomly, and puts together a quiz for students. Each quiz can be different and then reads a key to grade the quizzes. Sort Excel/CSV File Utility - Reads a file of records, sorts them, and then writes them back to the file. Allow the user to choose various sort style and sorting based on a particular field. Create Zip File Maker - The user enters various files from different directories and the program zips them up into a zip file. Optional: Apply actual compression to the files. Start with Huffman Algorithm. PDF Generator - An application that can read in a text file, HTML file, or some other file and generates a PDF file out of it. Great for a web-based service where the user uploads the file and the program returns a PDF of the file. Optional: Deploy on GAE or Heroku if possible. Mp3 Tagger - Modify and add ID3v1 tags to MP3 files. See if you can also add in the album art into the MP3 file’s header as well as other ID3v2 tags. Code Snippet Manager - Another utility program that allows coders to put in functions, classes, or other tidbits to save for use later. Organized by the type of snippet or language the coder can quickly lookup code. Optional: For extra practice try adding syntax highlighting based on the language. Databases SQL Query Analyzer - A utility application in which a user can enter a query and have it run against a local database and look for ways to make it more efficient. Remote SQL Tool - A utility that can execute queries on remote servers from your local computer across the Internet. It should take in a remote host, user name, and password, run the query and return the results. Report Generator - Create a utility that generates a report based on some tables in a database. Generates sales reports based on the order/order details tables or sums up the day's current database activity. Event Scheduler and Calendar - Make an application that allows the user to enter a date and time of an event, event notes, and then schedule those events on a calendar. The user can then browse the calendar or search the calendar for specific events. Optional: Allow the application to create re-occurrence events that reoccur every day, week, month, year, etc. Budget Tracker - Write an application that keeps track of a household’s budget. The user can add expenses, income, and recurring costs to find out how much they are saving or losing over a period of time. Optional: Allow the user to specify a date range and see the net flow of money in and out of the house budget for that time period. TV Show Tracker - Got a favorite show you don’t want to miss? Don’t have a PVR or want to be able to find the show to then PVR it later? Make an application that can search various online TV Guide sites, locate the shows/times/channels and add them to a database application. The database/website then can send you email reminders that a show is about to start and which channel it will be on. Travel Planner System - Make a system that allows users to put together their own little travel itinerary and keep track of the airline/hotel arrangements, points of interest, budget, and schedule. Graphics and Multimedia Slide Show - Make an application that shows various pictures in a slide show format. Optional: Try adding various effects like fade in/out, star wipe, and window blinds transitions. Stream Video from Online - Try to create your own online streaming video player. Mp3 Player - A simple program for playing your favorite music files. Add features you think are missing from your favorite music player. Watermarking Application - Have some pictures you want copyright protected? Add your own logo or text lightly across the background so that no one can simply steal your graphics off your site. Make a program that will add this watermark to the picture. Optional: Use threading to process multiple images simultaneously. Turtle Graphics - This is a common project where you create a floor of 20 x 20 squares. Using various commands you tell a turtle to draw a line on the floor. You have moved forward, left or right, lift or drop the pen, etc. Do a search online for "Turtle Graphics" for more information. Optional: Allow the program to read in the list of commands from a file. GIF Creator A program that puts together multiple images (PNGs, JPGs, TIFFs) to make a smooth GIF that can be exported. Optional: Make the program convert small video files to GIFs as well. Security Caesar cipher - Implement a Caesar cipher, both encoding, and decoding. The key is an integer from 1 to 25. This cipher rotates the letters of the alphabet (A to Z). The encoding replaces each letter with the 1st to 25th next letter in the alphabet (wrapping Z to A). So key 2 encrypts "HI" to "JK", but key 20 encrypts "HI" to "BC". This simple "monoalphabetic substitution cipher" provides almost no security, because an attacker who has the encoded message can either use frequency analysis to guess the key, or just try all 25 keys.
CourtBouillon / PydyfA low-level PDF creator
CNTRUN / Termux Commandchar const* const commands[] = { "aapt", " aapt", " zipalign", "abduco", " abduco", "abook", " abook", "alpine", " alpine", " pico", " pilot", " rpdump", " rpload", "angband", " angband", "apache2", " ab", " apachectl", " apxs", " checkgid", " dbmmanage", " envvars-std", " fcgistarter", " htcacheclean", " htdbm", " htdigest", " htpasswd", " httpd", " httxt2dbm", " logresolve", " rotatelogs", " suexec", "apr-dev", " apr-1-config", "apr-util-dev", " apu-1-config", "apt", " apt", " apt-cache", " apt-config", " apt-get", " apt-key", " apt-mark", "aria2", " aria2c", "atomicparsley", " AtomicParsley", "attr", " attr", " getfattr", " setfattr", "autossh", " autossh", "bash", " bash", "bc", " bc", " dc", "binutils", " addr2line", " ar", " arm-linux-androideabi-ar", " arm-linux-androideabi-ld", " arm-linux-androideabi-nm", " arm-linux-androideabi-objdump", " arm-linux-androideabi-ranlib", " arm-linux-androideabi-readelf", " arm-linux-androideabi-strip", " as", " c++filt", " elfedit", " gprof", " ld", " ldd", " nm", " objcopy", " objdump", " ranlib", " readelf", " size", " strings", " strip", "bison", " bison", " yacc", "blogc", " blogc", " blogc-make", " blogc-runserver", "bmon", " bmon", "brogue", " brogue", "bs1770gain", " bs1770gain", "bsdtar", " bsdcat", " bsdcpio", " bsdtar", "busybox", " busybox", " env", "bvi", " bmore", " bvedit", " bvi", " bview", "bzip2", " bunzip2", " bzcat", " bzcmp", " bzdiff", " bzgrep", " bzip2", " bzip2recover", " bzless", " bzmore", "cadaver", " cadaver", "calcurse", " calcurse", " calcurse-caldav", " calcurse-upgrade", "cava", " cava", "cboard", " cboard", "ccache", " ccache", "ccrypt", " ccat", " ccdecrypt", " ccencrypt", " ccguess", " ccrypt", "cgdb", " cgdb", "clang", " arm-linux-androideabi-clang", " arm-linux-androideabi-clang++", " arm-linux-androideabi-cpp", " arm-linux-androideabi-g++", " arm-linux-androideabi-gcc", " c++", " cc", " clang", " clang++", " clang-5.0", " clang-cl", " clang-cpp", " clang-format", " clang-rename", " cpp", " g++", " gcc", "cmake", " cmake", " cpack", " ctest", "cmake-curses-gui", " ccmake", "cmark", " cmark", "cmatrix", " cmatrix", "cmus", " cmus", " cmus-remote", "coreutils", " [", " b2sum", " base32", " base64", " basename", " cat", " chcon", " chgrp", " chmod", " chown", " cksum", " comm", " coreutils", " cp", " csplit", " cut", " date", " dd", " dir", " dircolors", " dirname", " du", " echo", " expand", " expr", " factor", " false", " fmt", " fold", " groups", " head", " id", " install", " join", " kill", " link", " ln", " logname", " ls", " md5sum", " mkdir", " mkfifo", " mknod", " mktemp", " mv", " nice", " nl", " nohup", " nproc", " numfmt", " od", " paste", " pathchk", " pr", " printenv", " printf", " ptx", " pwd", " readlink", " realpath", " rm", " rmdir", " runcon", " seq", " sha1sum", " sha224sum", " sha256sum", " sha384sum", " sha512sum", " shred", " shuf", " sleep", " sort", " split", " stat", " stdbuf", " stty", " sum", " sync", " tac", " tail", " tee", " test", " timeout", " touch", " tr", " true", " truncate", " tsort", " tty", " uname", " unexpand", " uniq", " unlink", " vdir", " wc", " whoami", " yes", "corkscrew", " corkscrew", "cpio", " cpio", "cppi", " cppi", "cscope", " cscope", " ocs", "ctags", " ctags", " readtags", "curl", " curl", "curseofwar", " curseofwar", "cvs", " cvs", " rcs2log", "daemonize", " daemonize", "darkhttpd", " darkhttpd", "dash", " dash", " sh", "datamash", " datamash", "db", " db_archive", " db_checkpoint", " db_convert", " db_deadlock", " db_dump", " db_hotbackup", " db_load", " db_log_verify", " db_printlog", " db_recover", " db_replicate", " db_stat", " db_tuner", " db_upgrade", " db_verify", "dcraw", " dcraw", "ddrescue", " ddrescue", " ddrescuelog", "debianutils", " add-shell", " ischroot", " remove-shell", " run-parts", " savelog", " tempfile", " which", "dialog", " dialog", " whiptail", "diffutils", " cmp", " diff", " diff3", " sdiff", "direvent", " direvent", "dirmngr", " dirmngr", " dirmngr-client", "dnsutils", " dig", " host", " nslookup", " nsupdate", "dos2unix", " dos2unix", " mac2unix", " unix2dos", " unix2mac", "dpkg", " dpkg", " dpkg-deb", " dpkg-divert", " dpkg-genbuildinfo", " dpkg-query", " dpkg-split", " dpkg-trigger", "dropbear", " dbclient", " dropbear", " dropbearconvert", " dropbearkey", " dropbearmulti", "dvtm", " dvtm", " dvtm-status", "ed", " ed", " red", "elfutils", " eu-addr2line", " eu-elfcmp", " eu-elfcompress", " eu-elflint", " eu-findtextrel", " eu-make-debug-archive", " eu-nm", " eu-objdump", " eu-ranlib", " eu-readelf", " eu-size", " eu-stack", " eu-strings", " eu-strip", " eu-unstrip", "elinks", " elinks", "emacs", " ebrowse", " emacs", " emacs-25.3", " emacsclient", " etags", "erlang", " ct_run", " dialyzer", " epmd", " erl", " erlc", " escript", " run_erl", " to_erl", "espeak", " espeak", "expect", " autoexpect", " expect", " timed-read", " timed-run", " unbuffer", "fdupes", " fdupes", "ffmpeg", " ffmpeg", " ffprobe", "fftw-dev", " fftw-wisdom", " fftw-wisdom-to-conf", " fftwf-wisdom", " fftwl-wisdom", "figlet", " chkfont", " figlet", " figlist", " showfigfonts", "file", " file", "finch", " finch", "findutils", " find", " xargs", "fish", " column", " fish", " fish_indent", " fish_key_reader", "flac", " flac", " metaflac", "flex", " flex", " flex++", "fontconfig-utils", " fc-cache", " fc-cat", " fc-list", " fc-match", " fc-pattern", " fc-query", " fc-scan", " fc-validate", "fortune", " fortune", "fossil", " fossil", "freetype-dev", " freetype-config", "frobtads", " frob", " t3make", " tadsc", "frotz", " frotz", " zgames", "fsmon", " fsmon", "fwknop", " fwknop", "fzf", " fzf", " fzf-tmux", "gawk", " awk", " gawk", "gbt", " gbt", "gcal", " gcal", " gcal2txt", " tcal", " txt2gcal", "gdb", " gcore", " gdb", " gdbserver", "gdbm", " gdbm_dump", " gdbm_load", " gdbmtool", "gdk-pixbuf", " gdk-pixbuf-csource", " gdk-pixbuf-pixdata", " gdk-pixbuf-query-loaders", "gegl", " gcut", " gegl", " gegl-imgcmp", "getconf", " getconf", "gettext", " autopoint", " envsubst", " gettext", " gettext.sh", " gettextize", " msgattrib", " msgcat", " msgcmp", " msgcomm", " msgconv", " msgen", " msgexec", " msgfilter", " msgfmt", " msggrep", " msginit", " msgmerge", " msgunfmt", " msguniq", " ngettext", " recode-sr-latin", " xgettext", "ghostscript", " dvipdf", " eps2eps", " gs", " gsbj", " gsdj", " gsdj500", " gslj", " gslp", " gsnd", " lprsetup.sh", " pdf2dsc", " pdf2ps", " pf2afm", " pfbtopfa", " pphs", " printafm", " ps2ascii", " ps2epsi", " ps2pdf", " ps2pdf12", " ps2pdf13", " ps2pdf14", " ps2pdfwr", " ps2ps", " ps2ps2", " unix-lpr.sh", "gifsicle", " gifdiff", " gifsicle", "git", " git", " git-receive-pack", " git-upload-archive", " git-upload-pack", "glib-bin", " gapplication", " gdbus", " gio", " gio-querymodules", " glib-compile-resources", " glib-compile-schemas", " glib-genmarshal", " glib-mkenums", " gobject-query", " gresource", " gsettings", " gtester", "global", " global", " globash", " gozilla", " gtags", " gtags-cscope", " htags", " htags-server", "glulxe", " glulxe", "gmic", " gmic", "gnuchess", " gnuchess", "gnugo", " gnugo", "gnuit", " .gitaction", " gitaction", " gitdpkgname", " gitfm", " gitkeys", " gitmkdirs", " gitmount", " gitps", " gitregrep", " gitrfgrep", " gitrgrep", " gitunpack", " gitview", " gitwhich", " gitwipe", " gitxgrep", "gnupg", " gpg", " gpg-zip", " gpgsplit", "gnupg2", " addgnupghome", " applygnupgdefaults", " gpg-agent", " gpg-connect-agent", " gpg2", " gpgconf", " gpgparsemail", " gpgscm", " gpgsm", " gpgtar", " gpgv2", " kbxutil", " watchgnupg", "gnuplot", " gnuplot", "gnushogi", " gnushogi", "gnutls", " certtool", " gnutls-cli", " gnutls-cli-debug", " gnutls-serv", " ocsptool", " psktool", " srptool", "golang", " go", " gofmt", "gperf", " gperf", "gpgme", " gpgme-tool", "gpgme-dev", " gpgme-config", "gpgv", " gpgv", "gpsbabel", " gpsbabel", "graphicsmagick", " gm", "graphviz", " acyclic", " bcomps", " ccomps", " circo", " cluster", " diffimg", " dijkstra", " dot", " dot2gxl", " dot_builtins", " edgepaint", " fdp", " gc", " gml2gv", " graphml2gv", " gv2gml", " gv2gxl", " gvcolor", " gvgen", " gvmap", " gvmap.sh", " gvpack", " gvpr", " gxl2dot", " gxl2gv", " mm2gv", " neato", " nop", " osage", " patchwork", " prune", " sccmap", " sfdp", " tred", " twopi", " unflatten", "greed", " greed", "grep", " egrep", " fgrep", " grep", "gst-plugins-base", " gst-device-monitor-1.0", " gst-discoverer-1.0", " gst-play-1.0", "gstreamer", " gst-inspect-1.0", " gst-launch-1.0", " gst-stats-1.0", " gst-typefind-1.0", "gtypist", " gtypist", "gzip", " gunzip", " gzexe", " gzip", " uncompress", " zcat", " zcmp", " zdiff", " zegrep", " zfgrep", " zforce", " zgrep", " zless", " zmore", " znew", "harfbuzz-utils", " hb-ot-shape-closure", " hb-shape", " hb-view", "hashdeep", " hashdeep", " md5deep", " sha1deep", " sha256deep", " tigerdeep", " whirlpooldeep", "hexcurse", " hexcurse", "heyu", " heyu", "hfsutils", " hattrib", " hcd", " hcopy", " hdel", " hdir", " hformat", " hfsutil", " hls", " hmkdir", " hmount", " hpwd", " hrename", " hrmdir", " humount", " hvol", "htop", " htop", "httping", " httping", "hub", " hub", "hunspell", " affixcompress", " analyze", " chmorph", " hunspell", " hunzip", " hzip", " ispellaff2myspell", " makealias", " munch", " unmunch", " wordforms", " wordlist2hunspell", "hydra", " dpl4hydra.sh", " hydra", " hydra-wizard.sh", " pw-inspector", "icecast", " icecast", "iconv", " iconv", "icu-devtools", " derb", " escapesrc", " genbrk", " genccode", " gencfu", " gencmn", " gencnval", " gendict", " gennorm2", " genrb", " gensprep", " icu-config", " icuinfo", " icupkg", " makeconv", " pkgdata", " uconv", "imagemagick", " animate", " compare", " composite", " conjure", " convert", " display", " identify", " import", " magick", " magick-script", " mogrify", " montage", " stream", "imgflo", " imgflo", " imgflo-graphinfo", " imgflo-runtime", "inetutils", " dnsdomainname", " ftp", " logger", " telnet", " tftp", " whois", "inotify-tools", " inotifywait", " inotifywatch", "iperf3", " iperf3", "ired", " bdiff", " ired", " vired", "irssi", " irssi", "jhead", " jhead", "joe", " jmacs", " joe", " jpico", " jstar", " rjoe", "jq", " jq", "jupp", " jmacs", " joe", " jpico", " jstar", " jupp", " rjoe", "kona", " k", "krb5", " compile_et", " gss-client", " gss-server", " k5srvutil", " kadmin", " kadmin.local", " kadmind", " kdb5_util", " kdestroy", " kinit", " klist", " kpasswd", " kprop", " kpropd", " kproplog", " krb5-config", " krb5-send-pr", " krb5kdc", " ksu", " kswitch", " ktutil", " kvno", " sclient", " sim_client", " sim_server", " sserver", " uuclient", " uuserver", "ldc", " dub", " ldc-build-runtime", " ldc2", " ldmd2", " rdmd", "ldns-dev", " ldns-config", "ledger", " ledger", "leptonica", " convertfilestopdf", " convertfilestops", " convertformat", " convertsegfilestopdf", " convertsegfilestops", " converttopdf", " converttops", " fileinfo", " xtractprotos", "less", " less", " lessecho", " lesskey", "lftp", " lftp", " lftpget", "libassuan-dev", " libassuan-config", "libcaca", " caca-config", " cacaclock", " cacademo", " cacafire", " cacaplay", " cacaserver", " cacaview", " img2txt", "libcairo", " cairo-trace", "libcroco", " croco-0.6-config", " csslint-0.6", "libcurl-dev", " curl-config", "libgcrypt", " dumpsexp", " hmac256", " libgcrypt-config", " mpicalc", "libgd", " annotate", " bdftogd", " gd2copypal", " gd2togif", " gd2topng", " gdcmpgif", " gdlib-config", " gdparttopng", " gdtopng", " giftogd2", " pngtogd", " pngtogd2", " webpng", "libgpg-error", " gpg-error", " gpg-error-config", "libgrpc", " check_epollexclusive", " gen_hpack_tables", " gen_legal_metadata_characters", " gen_percent_encoding_tables", " grpc_cpp_plugin", " grpc_create_jwt", " grpc_csharp_plugin", " grpc_node_plugin", " grpc_objective_c_plugin", " grpc_php_plugin", " grpc_print_google_default_creds_token", " grpc_python_plugin", " grpc_ruby_plugin", " grpc_verify_jwt", "libjasper-utils", " imgcmp", " imginfo", " jasper", "libjpeg-turbo-progs", " cjpeg", " djpeg", " jpegtran", " rdjpgcom", " tjbench", " wrjpgcom", "libksba-dev", " ksba-config", "libnpth", " npth-config", "liboggz", " oggz", " oggz-chop", " oggz-codecs", " oggz-comment", " oggz-diff", " oggz-dump", " oggz-info", " oggz-known-codecs", " oggz-merge", " oggz-rip", " oggz-scan", " oggz-sort", " oggz-validate", "libotr", " otr_mackey", " otr_modify", " otr_parse", " otr_readforge", " otr_remac", " otr_sesskeys", "libpng-dev", " libpng-config", " libpng16-config", "librsvg", " rsvg-convert", "libtiff-utils", " fax2ps", " fax2tiff", " pal2rgb", " ppm2tiff", " raw2tiff", " tiff2bw", " tiff2pdf", " tiff2ps", " tiff2rgba", " tiffcmp", " tiffcp", " tiffcrop", " tiffdither", " tiffdump", " tiffinfo", " tiffmedian", " tiffset", " tiffsplit", "libtool", " libtool", " libtoolize", "libxapian-dev", " xapian-config", "libxml2-dev", " xml2-config", "libxml2-utils", " xmlcatalog", " xmllint", "libxslt-dev", " xslt-config", "libzmq", " curve_keygen", "lighttpd", " lighttpd", "littlecms-utils", " jpgicc", " linkicc", " psicc", " tificc", " transicc", "lld", " ld.lld", " lld", " lld-link", "llvm", " llc", " lli", " llvm-ar", " llvm-as", " llvm-bcanalyzer", " llvm-c-test", " llvm-cat", " llvm-config", " llvm-cov", " llvm-cvtres", " llvm-cxxdump", " llvm-cxxfilt", " llvm-diff", " llvm-dis", " llvm-dlltool", " llvm-dsymutil", " llvm-dwarfdump", " llvm-dwp", " llvm-extract", " llvm-lib", " llvm-link", " llvm-lto", " llvm-lto2", " llvm-mc", " llvm-mcmarkup", " llvm-modextract", " llvm-mt", " llvm-nm", " llvm-objdump", " llvm-opt-report", " llvm-pdbutil", " llvm-profdata", " llvm-ranlib", " llvm-readelf", " llvm-readobj", " llvm-rtdyld", " llvm-size", " llvm-split", " llvm-stress", " llvm-strings", " llvm-symbolizer", " llvm-xray", " obj2yaml", " opt", " verify-uselistorder", " yaml2obj", "ltrace", " ltrace", "lua", " lua", " luac", "lynx", " lynx", "lzip", " lzip", "lzop", " lzop", "m4", " m4", "macchanger", " macchanger", "make", " make", "man", " apropos", " demandoc", " makewhatis", " man", " mandoc", " soelim", " whatis", "mariadb", " aria_chk", " aria_dump_log", " aria_ftdump", " aria_pack", " aria_read_log", " innochecksum", " mariadb_config", " msql2mysql", " my_print_defaults", " myisam_ftdump", " myisamchk", " myisamlog", " myisampack", " mysql", " mysql_client_test", " mysql_config", " mysql_convert_table_format", " mysql_find_rows", " mysql_fix_extensions", " mysql_install_db", " mysql_plugin", " mysql_secure_installation", " mysql_setpermission", " mysql_tzinfo_to_sql", " mysql_upgrade", " mysql_waitpid", " mysqlaccess", " mysqladmin", " mysqlbinlog", " mysqlcheck", " mysqld", " mysqld_multi", " mysqld_safe", " mysqld_safe_helper", " mysqldump", " mysqldumpslow", " mysqlhotcopy", " mysqlimport", " mysqlshow", " mysqlslap", " mytop", " perror", " replace", " resolve_stack_dump", " resolveip", "mathomatic", " mathomatic", "mc", " mc", " mcdiff", " mcedit", " mcview", "megatools", " megacopy", " megadf", " megadl", " megaget", " megals", " megamkdir", " megaput", " megareg", " megarm", "memcached", " memcached", "micro", " micro", "minicom", " ascii-xfr", " minicom", " runscript", " xminicom", "mlocate", " locate", " updatedb", "moon-buggy", " moon-buggy", "moria", " moria", "mosh", " mosh", " mosh-client", " mosh-server", " mosh.pl", "mosquitto", " mosquitto", " mosquitto_passwd", " mosquitto_pub", " mosquitto_sub", "mp3splt", " mp3splt", "mpc", " mpc", "mpd", " mpd", "mpv", " mpv", "mtools", " amuFormat.sh", " lz", " mattrib", " mbadblocks", " mcat", " mcd", " mcheck", " mclasserase", " mcomp", " mcopy", " mdel", " mdeltree", " mdir", " mdu", " mformat", " minfo", " mkmanifest", " mlabel", " mmd", " mmount", " mmove", " mpartition", " mrd", " mren", " mshortname", " mshowfat", " mtools", " mtoolstest", " mtype", " mxtar", " mzip", " tgz", " uz", "multitail", " multitail", "mutt", " mutt", " pgpewrap", " pgpring", " smime_keys", "nano", " nano", "ncdc", " ncdc", "ncdu", " ncdu", "ncmpcpp", " ncmpcpp", "ncurses-dev", " ncursesw6-config", "ncurses-utils", " clear", " infocmp", " reset", " tabs", " tic", " toe", " tput", " tset", "ne", " ne", "neovim", " nvim", "net-tools", " arp", " ifconfig", " ipmaddr", " iptunnel", " mii-tool", " nameif", " netstat", " plipconfig", " rarp", " route", " slattach", "netcat", " nc", " ncat", " netcat", "netpbm", " 411toppm", " anytopnm", " asciitopgm", " atktopbm", " avstopam", " bioradtopgm", " bmptopnm", " bmptoppm", " brushtopbm", " cameratopam", " cistopbm", " cmuwmtopbm", " ddbugtopbm", " escp2topbm", " eyuvtoppm", " fiascotopnm", " fitstopnm", " fstopgm", " g3topbm", " gemtopbm", " gemtopnm", " giftopnm", " gouldtoppm", " hdifftopam", " hipstopgm", " hpcdtoppm", " icontopbm", " ilbmtoppm", " imgtoppm", " infotopam", " jbigtopnm", " jpeg2ktopam", " jpegtopnm", " leaftoppm", " lispmtopgm", " macptopbm", " manweb", " mdatopbm", " mgrtopbm", " mrftopbm", " mtvtoppm", " neotoppm", " netpbm-config", " palmtopnm", " pamaddnoise", " pamarith", " pambackground", " pambayer", " pamchannel", " pamcomp", " pamcrater", " pamcut", " pamdeinterlace", " pamdepth", " pamdice", " pamditherbw", " pamedge", " pamendian", " pamenlarge", " pamexec", " pamfile", " pamfix", " pamfixtrunc", " pamflip", " pamfunc", " pamgauss", " pamgradient", " pamlookup", " pammasksharpen", " pammixinterlace", " pammosaicknit", " pamoil", " pampaintspill", " pamperspective", " pampick", " pampop9", " pamrecolor", " pamrgbatopng", " pamrubber", " pamscale", " pamseq", " pamshadedrelief", " pamsharpmap", " pamsharpness", " pamsistoaglyph", " pamslice", " pamsplit", " pamstack", " pamstereogram", " pamstretch", " pamstretch-gen", " pamsumm", " pamsummcol", " pamtable", " pamthreshold", " pamtilt", " pamtoavs", " pamtodjvurle", " pamtofits", " pamtogif", " pamtohdiff", " pamtohtmltbl", " pamtojpeg2k", " pamtompfont", " pamtooctaveimg", " pamtopam", " pamtopdbimg", " pamtopfm", " pamtopng", " pamtopnm", " pamtosrf", " pamtosvg", " pamtotga", " pamtotiff", " pamtouil", " pamtowinicon", " pamtoxvmini", " pamundice", " pamunlookup", " pamvalidate", " pamwipeout", " pbmclean", " pbmlife", " pbmmake", " pbmmask", " pbmminkowski", " pbmpage", " pbmpscale", " pbmreduce", " pbmtext", " pbmtextps", " pbmto10x", " pbmto4425", " pbmtoascii", " pbmtoatk", " pbmtobbnbg", " pbmtocis", " pbmtocmuwm", " pbmtodjvurle", " pbmtoepsi", " pbmtoepson", " pbmtoescp2", " pbmtog3", " pbmtogem", " pbmtogo", " pbmtoibm23xx", " pbmtoicon", " pbmtolj", " pbmtoln03", " pbmtolps", " pbmtomacp", " pbmtomatrixorbital", " pbmtomda", " pbmtomgr", " pbmtomrf", " pbmtonokia", " pbmtopgm", " pbmtopi3", " pbmtopk", " pbmtoplot", " pbmtoppa", " pbmtopsg3", " pbmtoptx", " pbmtosunicon", " pbmtowbmp", " pbmtox10bm", " pbmtoxbm", " pbmtoybm", " pbmtozinc", " pbmupc", " pc1toppm", " pcdovtoppm", " pcxtoppm", " pdbimgtopam", " pfmtopam", " pgmabel", " pgmbentley", " pgmcrater", " pgmdeshadow", " pgmedge", " pgmenhance", " pgmhist", " pgmkernel", " pgmmake", " pgmmedian", " pgmminkowski", " pgmmorphconv", " pgmnoise", " pgmnorm", " pgmoil", " pgmramp", " pgmslice", " pgmtexture", " pgmtofs", " pgmtolispm", " pgmtopbm", " pgmtopgm", " pgmtoppm", " pgmtosbig", " pgmtost4", " pi1toppm", " pi3topbm", " picttoppm", " pjtoppm", " pktopbm", " pngtopam", " pngtopnm", " pnmalias", " pnmarith", " pnmcat", " pnmcolormap", " pnmcomp", " pnmconvol", " pnmcrop", " pnmcut", " pnmdepth", " pnmenlarge", " pnmfile", " pnmflip", " pnmgamma", " pnmhisteq", " pnmhistmap", " pnmindex", " pnminterp", " pnminvert", " pnmmargin", " pnmmercator", " pnmmontage", " pnmnlfilt", " pnmnoraw", " pnmnorm", " pnmpad", " pnmpaste", " pnmpsnr", " pnmquant", " pnmquantall", " pnmremap", " pnmrotate", " pnmscale", " pnmscalefixed", " pnmshear", " pnmsmooth", " pnmsplit", " pnmstitch", " pnmtile", " pnmtoddif", " pnmtofiasco", " pnmtofits", " pnmtojbig", " pnmtojpeg", " pnmtopalm", " pnmtopclxl", " pnmtoplainpnm", " pnmtopng", " pnmtopnm", " pnmtops", " pnmtorast", " pnmtorle", " pnmtosgi", " pnmtosir", " pnmtotiff", " pnmtotiffcmyk", " pnmtoxwd", " ppm3d", " ppmbrighten", " ppmchange", " ppmcie", " ppmcolormask", " ppmcolors", " ppmdcfont", " ppmddumpfont", " ppmdim", " ppmdist", " ppmdither", " ppmdmkfont", " ppmdraw", " ppmfade", " ppmflash", " ppmforge", " ppmglobe", " ppmhist", " ppmlabel", " ppmmake", " ppmmix", " ppmnorm", " ppmntsc", " ppmpat", " ppmquant", " ppmquantall", " ppmrainbow", " ppmrelief", " ppmrough", " ppmshadow", " ppmshift", " ppmspread", " ppmtoacad", " ppmtoapplevol", " ppmtoarbtxt", " ppmtoascii", " ppmtobmp", " ppmtoeyuv", " ppmtogif", " ppmtoicr", " ppmtoilbm", " ppmtojpeg", " ppmtoleaf", " ppmtolj", " ppmtomap", " ppmtomitsu", " ppmtompeg", " ppmtoneo", " ppmtopcx", " ppmtopgm", " ppmtopi1", " ppmtopict", " ppmtopj", " ppmtopjxl", " ppmtoppm", " ppmtopuzz", " ppmtorgb3", " ppmtosixel", " ppmtospu", " ppmtoterm", " ppmtotga", " ppmtouil", " ppmtowinicon", " ppmtoxpm", " ppmtoyuv", " ppmtoyuvsplit", " ppmtv", " ppmwheel", " psidtopgm", " pstopnm", " qrttoppm", " rasttopnm", " rawtopgm", " rawtoppm", " rgb3toppm", " rlatopam", " rletopnm", " sbigtopgm", " sgitopnm", " sirtopnm", " sldtoppm", " spctoppm", " spottopgm", " sputoppm", " srftopam", " st4topgm", " sunicontopnm", " svgtopam", " tgatoppm", " thinkjettopbm", " tifftopnm", " wbmptopbm", " winicontopam", " winicontoppm", " xbmtopbm", " ximtoppm", " xpmtoppm", " xvminitoppm", " xwdtopnm", " ybmtopbm", " yuvsplittoppm", " yuvtoppm", " yuy2topam", " zeisstopnm", "nettle", " nettle-hash", " nettle-lfib-stream", " nettle-pbkdf2", " pkcs1-conv", " sexp-conv", "newsboat", " newsboat", " podboat", "nginx", " nginx", "ninja", " ninja", "nmap", " nmap", " nping", "nodejs", " node", " npm", " npx", "nodejs-current", " node", " npm", " npx", "notmuch", " notmuch", "nyancat", " nyancat", "nzbget", " nzbget", "oathtool", " oathtool", " pskctool", "ocrad", " ocrad", "openjpeg-tools", " opj_compress", " opj_decompress", " opj_dump", "openssh", " scp", " sftp", " source-ssh-agent", " ssh", " ssh-add", " ssh-agent", " ssh-copy-id", " ssh-keygen", " ssh-keyscan", " ssha", " sshd", "openssl-tool", " openssl", "optipng", " optipng", "opus-tools", " opusdec", " opusenc", " opusinfo", "p7zip", " 7z", " 7za", " 7zr", "pango", " pango-view", "par2", " par2", " par2create", " par2repair", " par2verify", "patch", " patch", "patchelf", " patchelf", "pcre-dev", " pcre-config", "pcre2-dev", " pcre2-config", "perl", " corelist", " cpan", " enc2xs", " encguess", " h2ph", " h2xs", " instmodsh", " json_pp", " libnetcfg", " perl", " perlbug", " perldoc", " perlivp", " perlthanks", " piconv", " pl2pm", " pod2html", " pod2man", " pod2text", " pod2usage", " podchecker", " podselect", " prove", " ptar", " ptardiff", " ptargrep", " shasum", " splain", " xsubpp", " zipdetails", "pforth", " pforth", "php", " phar", " phar.phar", " php", " php-cgi", " php-config", " phpdbg", " phpize", "php-fpm", " php-fpm", "pick", " pick", "picolisp", " picolisp", " pil", "pinentry", " pinentry", " pinentry-curses", "pkg-config", " pkg-config", "play-audio", " play-audio", "pngquant", " pngquant", "poppler", " pdfdetach", " pdffonts", " pdfimages", " pdfinfo", " pdfseparate", " pdftocairo", " pdftohtml", " pdftoppm", " pdftops", " pdftotext", " pdfunite", "postgresql", " clusterdb", " createdb", " createuser", " dropdb", " dropuser", " initdb", " pg_archivecleanup", " pg_basebackup", " pg_config", " pg_controldata", " pg_ctl", " pg_dump", " pg_dumpall", " pg_isready", " pg_receivewal", " pg_recvlogical", " pg_resetwal", " pg_restore", " pg_rewind", " pg_test_fsync", " pg_test_timing", " pg_upgrade", " pg_waldump", " pgbench", " postgres", " postmaster", " psql", " reindexdb", " vacuumdb", "potrace", " mkbitmap", " potrace", "privoxy", " privoxy", "procps", " free", " pgrep", " pidof", " pkill", " pmap", " ps", " pwdx", " slabtop", " sysctl", " tload", " top", " uptime", " vmstat", " w", " watch", "profanity", " profanity", "proot", " proot", " termux-chroot", "protobuf", " protoc", "psmisc", " fuser", " killall", " peekfd", " prtstat", " pstree", "pulseaudio", " esdcompat", " pacat", " pacmd", " pactl", " pasuspender", " pulseaudio", "pure-ftpd", " pure-authd", " pure-ftpd", " pure-ftpwho", " pure-mrtginfo", " pure-pw", " pure-pwconvert", " pure-quotacheck", " pure-statsdecode", " pure-uploadscript", "pv", " pv", "pwgen", " pwgen", "python", " 2to3", " 2to3-3.6", " pydoc3", " pydoc3.6", " python", " python3", " python3-config", " python3.6", " python3.6-config", " python3.6m-config", " pyvenv", " pyvenv-3.6", "python2", " idle", " pydoc", " python-config", " python2", " python2-config", " python2.7", " python2.7-config", " smtpd.py", "qalc", " qalc", "qpdf", " fix-qdf", " qpdf", " zlib-flate", "radare2", " r2", " r2agent", " r2pm", " rabin2", " radare2", " radiff2", " rafind2", " ragg2", " ragg2-cc", " rahash2", " rarun2", " rasm2", " rax2", "ragel", " ragel", "rcs", " ci", " co", " ident", " merge", " rcs", " rcsclean", " rcsdiff", " rcsmerge", " rlog", "rdiff", " rdiff", "redir", " redir", "redis", " redis-benchmark", " redis-check-aof", " redis-check-rdb", " redis-cli", " redis-sentinel", " redis-server", "remind", " rem", " rem2ps", " remind", "rgbds", " rgbasm", " rgbfix", " rgbgfx", " rgblink", "rlwrap", " rlwrap", "rsync", " rsync", "rtmpdump", " rtmpdump", " rtmpgw", " rtmpsrv", " rtmpsuck", "ruby", " erb", " gem", " irb", " rake", " rdoc", " ruby", "screen", " screen", " screen-4.6.2", "scrypt", " scrypt", "sed", " sed", "sensible-utils", " select-editor", " sensible-browser", " sensible-editor", " sensible-pager", "sharutils", " shar", " unshar", " uudecode", " uuencode", "silversearcher-ag", " ag", "sl", " sl", "socat", " filan", " procan", " socat", "sox", " play", " rec", " sox", " soxi", "sqlite", " sqlite3", "squid", " purge", " squid", " squidclient", "sshpass", " sshpass", "sslscan", " sslscan", "stag", " stag", "strace", " strace", " strace-log-merge", "stunnel", " stunnel", "subversion", " svn", " svnadmin", " svnbench", " svndumpfilter", " svnfsfs", " svnlook", " svnmucc", " svnrdump", " svnserve", " svnsync", " svnversion", "syncthing", " syncthing", "tar", " tar", "tasksh", " tasksh", "taskwarrior", " task", "tcl", " sqlite3_analyzer", " tclsh", " tclsh8.6", "tcsh", " tcsh", "teckit", " sfconv", " teckit_compile", " txtconv", "termux-api", " termux-audio-info", " termux-battery-status", " termux-camera-info", " termux-camera-photo", " termux-clipboard-get", " termux-clipboard-set", " termux-contact-list", " termux-dialog", " termux-download", " termux-infrared-frequencies", " termux-infrared-transmit", " termux-location", " termux-media-scan", " termux-notification", " termux-notification-remove", " termux-share", " termux-sms-inbox", " termux-sms-send", " termux-storage-get", " termux-telephony-call", " termux-telephony-cellinfo", " termux-telephony-deviceinfo", " termux-toast", " termux-tts-engines", " termux-tts-speak", " termux-vibrate", " termux-wifi-connectioninfo", " termux-wifi-scaninfo", "termux-elf-cleaner", " termux-elf-cleaner", "teseq", " reseq", " teseq", "tesseract", " tesseract", "texinfo", " info", " install-info", " makeinfo", " pdftexi2dvi", " pod2texi", " texi2any", " texi2dvi", " texi2pdf", " texindex", "texlive-bin", " a2ping", " a5toa4", " adhocfilelist", " afm2afm", " afm2pl", " afm2tfm", " aleph", " allcm", " allec", " allneeded", " arara", " arlatex", " authorindex", " autoinst", " autosp", " bbl2bib", " bbox", " bg5+latex", " bg5+pdflatex", " bg5conv", " bg5latex", " bg5pdflatex", " bibdoiadd", " bibexport", " bibmradd", " bibtex", " bibtex8", " bibzbladd", " bundledoc", " cachepic", " cef5conv", " cef5latex", " cef5pdflatex", " cefconv", " ceflatex", " cefpdflatex", " cefsconv", " cefslatex", " cefspdflatex", " cfftot1", " checkcites", " checklistings", " chktex", " chkweb", " cjk-gs-integrate", " context", " contextjit", " convbkmk", " ctangle", " ctanify", " ctanupload", " ctie", " cweave", " 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kpsereadlink", " kpsestat", " kpsetool", " kpsewhere", " kpsewhich", " kpsexpand", " lacheck", " latex-git-log", " latex-papersize", " latex2man", " latex2nemeth", " latexdiff", " latexdiff-vc", " latexfileversion", " latexindent", " latexmk", " latexpand", " latexrevise", " lily-glyph-commands", " lily-image-commands", " lily-rebuild-pdfs", " listbib", " listings-ext.sh", " ltx2crossrefxml", " ltxfileinfo", " ltximg", " lua2dox_filter", " luaotfload-tool", " luatex", " luatools", " lwarpmk", " m-tx", " make4ht", " makedtx", " makeglossaries", " makeglossaries-lite", " makeindex", " match_parens", " mathspic", " mf", " mf-nowin", " mf2pt1", " mfplain", " mft", " mk4ht", " mkgrkindex", " mkindex", " mkjobtexmf", " mkocp", " mkofm", " mkpic", " mkt1font", " mktexfmt", " mktexlsr", " mktexmf", " mktexpk", " mktextfm", " mmafm", " mmpfb", " mpost", " mptopdf", " mtxrun", " mtxrunjit", " multibibliography", " musixflx", " musixtex", " odvicopy", " odvitype", " ofm2opl", " omfonts", " opl2ofm", " ot2kpx", " otangle", " otfinfo", " otftotfm", " otp2ocp", " outocp", " ovf2ovp", " ovp2ovf", " patgen", " pbibtex", " pdf180", " pdf270", " pdf90", " pdfannotextractor", " pdfatfi", " pdfbook", " pdfbook2", " pdfcrop", " pdfflip", " pdfjam", " pdfjam-pocketmod", " pdfjam-slides3up", " pdfjam-slides6up", " pdfjoin", " pdflatexpicscale", " pdfnup", " pdfpun", " pdftex", " pdftosrc", " pdfxup", " pdvitomp", " pdvitype", " pedigree", " perltex", " pfarrei", " pkfix", " pkfix-helper", " pktogf", " pktype", " pltotf", " pmpost", " pmxchords", " pn2pdf", " pooltype", " ppltotf", " prepmx", " ps2eps", " ps2frag", " ps4pdf", " pslatex", " pst2pdf", " ptex", " ptex2pdf", " ptftopl", " purifyeps", " pygmentex", " pythontex", " repstopdf", " rpdfcrop", " rubibtex", " rubikrotation", " rumakeindex", " rungs", " simpdftex", " sjisconv", " sjislatex", " sjispdflatex", " splitindex", " srcredact", " sty2dtx", " svn-multi", " synctex", " t1dotlessj", " t1lint", " t1rawafm", " t1reencode", " t1testpage", " t4ht", " tangle", " tex", " tex4ebook", " tex4ht", " texconfig", " texconfig-dialog", " texconfig-sys", " texcount", " texdef", " texdiff", " texdirflatten", " texdoc", " texdoctk", " texexec", " texfot", " texhash", " texlinks", " texliveonfly", " texloganalyser", " texlua", " texluac", " texmfstart", " texosquery", " texosquery-jre5", " texosquery-jre8", " tftopl", " thumbpdf", " tie", " tlmgr", " tlmgr.ln", " tpic2pdftex", " ttf2afm", " ttf2kotexfont", " ttf2pk", " ttf2tfm", " ttftotype42", " typeoutfileinfo", " ulqda", " upbibtex", " updmap", " updmap-sys", " updmap-user", " updvitomp", " updvitype", " upmendex", " upmpost", " uppltotf", " uptex", " uptftopl", " urlbst", " vftovp", " vlna", " vpe", " vpl2ovp", " vpl2vpl", " vptovf", " weave", " wofm2opl", " wopl2ofm", " wovf2ovp", " wovp2ovf", " xdvipdfmx", " xetex", " xhlatex", " yplan", "tig", " tig", "timewarrior", " timew", "tintin++", " tt++", "tinyscheme", " tinyscheme", "tmate", " tmate", "tmux", " tmux", "toilet", " toilet", "tor", " tor", " tor-gencert", " tor-resolve", " torify", "torsocks", " torsocks", "tracepath", " tracepath", " traceroute", "transmission", " transmission-create", " transmission-daemon", " transmission-edit", " transmission-remote", " transmission-show", "tree", " tree", "tsocks", " tsocks", "tty-clock", " tty-clock", "tty-solitaire", " ttysolitaire", "ttyrec", " ttyplay", " ttyrec", " ttytime", "units", " units", " units_cur", "unrar", " unrar", "unzip", " funzip", " unzip", " unzipsfx", " zipgrep", " zipinfo", "utfdecode", " utfdecode", "util-linux", " addpart", " blkdiscard", " blkid", " blkzone", " blockdev", " cal", " chcpu", " chrt", " col", " colcrt", " colrm", " ctrlaltdel", " delpart", " dmesg", " fallocate", " fdformat", " fincore", " findfs", " flock", " fsck.cramfs", " fsck.minix", " fsfreeze", " getopt", " hexdump", " hwclock", " ionice", " isosize", " ldattach", " linux32", " linux64", " look", " losetup", " lscpu", " lsipc", " lsns", " mcookie", " mesg", " mkfs", " mkfs.bfs", " mkfs.cramfs", " mkfs.minix", " mkswap", " more", " namei", " nologin", " nsenter", " partx", " prlimit", " raw", " readprofile", " rename", " renice", " resizepart", " rev", " rtcwake", " script", " scriptreplay", " setarch", " setsid", " setterm", " swaplabel", " taskset", " ul", " uname26", " unshare", " wdctl", " whereis", " wipefs", " zramctl", "valac", " vala", " vala-0.38", " vala-gen-introspect", " vala-gen-introspect-0.38", " valac", " valac-0.38", " vapicheck", " vapicheck-0.38", " vapigen", " vapigen-0.38", "valadoc", " valadoc", " valadoc-0.38", "valgrind", " callgrind_annotate", " callgrind_control", " cg_annotate", " cg_diff", " cg_merge", " ms_print", " valgrind", " valgrind-di-server", " valgrind-listener", " vgdb", "vifm", " vifm", " vifm-convert-dircolors", " vifm-pause", " vifm-screen-split", "vim", " vi", " view", " vim", " vimdiff", " vimtutor", " xxd", "vim-python", " vi", " view", " vim", " vimdiff", " vimtutor", " xxd", "vorbis-tools", " oggdec", " oggenc", " ogginfo", " vcut", " vorbiscomment", "vttest", " vttest", "vtutils", " vtquery", " vtshowkeys", " vtsize", " vttitle", "w3m", " w3m", " w3mman", "wcalc", " wcalc", "weechat", " weechat", "wget", " wget", "wol", " wol", " wol-bootptab", " wol-dhcpdconf", "x264", " x264", "x265", " x265", "xapian-tools", " copydatabase", " quest", " simpleexpand", " simpleindex", " simplesearch", " xapian-check", " xapian-compact", " xapian-delve", " xapian-metadata", " xapian-progsrv", " xapian-replicate", " xapian-replicate-server", " xapian-tcpsrv", "xmlsec", " xmlsec1", " xmlsec1-config", "xmlstarlet", " xml", "xorriso", " osirrox", " xorrecord", " xorriso", " xorriso-tcltk", " xorrisofs", "xsltproc", " xsltproc", "xz-utils", " lzcat", " lzcmp", " lzdiff", " lzegrep", " lzfgrep", " lzgrep", " lzless", " lzma", " lzmadec", " lzmainfo", " lzmore", " unlzma", " unxz", " xz", " xzcat", " xzcmp", " xzdec", " xzdiff", " xzegrep", " xzfgrep", " xzgrep", " xzless", " xzmore", "yasm", " vsyasm", " yasm", " ytasm", "zbar", " zbarimg", "zile", " zile", "zip", " zip", " zipcloak", " zipnote", " zipsplit", "zsh", " zsh", "zstd", " unzstd", " zstd", " zstdcat", " zstdgrep", " zstdless", " zstdmt", "ack-grep", " ack", "apksigner", " apksigner", "asciinema", " asciinema", "autoconf", " autoconf", " autoheader", " autom4te", " autoreconf", " autoscan", " autoupdate", " ifnames", "automake", " aclocal", " aclocal-1.15", " automake", " automake-1.15", "byobu", " byobu", " byobu-config", " byobu-ctrl-a", " byobu-disable", " byobu-disable-prompt", " byobu-enable", " byobu-enable-prompt", " byobu-export", " byobu-janitor", " byobu-keybindings", " byobu-launch", " byobu-launcher", " byobu-launcher-install", " byobu-launcher-uninstall", " byobu-layout", " byobu-prompt", " byobu-quiet", " byobu-reconnect-sockets", " byobu-screen", " byobu-select-backend", " byobu-select-profile", " byobu-select-session", " byobu-shell", " byobu-silent", " byobu-status", " 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uvhw / Bitcoin FoundationBitcoin: A Peer-to-Peer Electronic Cash System Satoshi Nakamoto satoshin@gmx.com www.bitcoin.org Abstract. A purely peer-to-peer version of electronic cash would allow online payments to be sent directly from one party to another without going through a financial institution. Digital signatures provide part of the solution, but the main benefits are lost if a trusted third party is still required to prevent double-spending. We propose a solution to the double-spending problem using a peer-to-peer network. The network timestamps transactions by hashing them into an ongoing chain of hash-based proof-of-work, forming a record that cannot be changed without redoing the proof-of-work. The longest chain not only serves as proof of the sequence of events witnessed, but proof that it came from the largest pool of CPU power. As long as a majority of CPU power is controlled by nodes that are not cooperating to attack the network, they'll generate the longest chain and outpace attackers. The network itself requires minimal structure. Messages are broadcast on a best effort basis, and nodes can leave and rejoin the network at will, accepting the longest proof-of-work chain as proof of what happened while they were gone. 1. Introduction Commerce on the Internet has come to rely almost exclusively on financial institutions serving as trusted third parties to process electronic payments. While the system works well enough for most transactions, it still suffers from the inherent weaknesses of the trust based model. Completely non-reversible transactions are not really possible, since financial institutions cannot avoid mediating disputes. The cost of mediation increases transaction costs, limiting the minimum practical transaction size and cutting off the possibility for small casual transactions, and there is a broader cost in the loss of ability to make non-reversible payments for non- reversible services. With the possibility of reversal, the need for trust spreads. Merchants must be wary of their customers, hassling them for more information than they would otherwise need. A certain percentage of fraud is accepted as unavoidable. These costs and payment uncertainties can be avoided in person by using physical currency, but no mechanism exists to make payments over a communications channel without a trusted party. What is needed is an electronic payment system based on cryptographic proof instead of trust, allowing any two willing parties to transact directly with each other without the need for a trusted third party. Transactions that are computationally impractical to reverse would protect sellers from fraud, and routine escrow mechanisms could easily be implemented to protect buyers. In this paper, we propose a solution to the double-spending problem using a peer-to-peer distributed timestamp server to generate computational proof of the chronological order of transactions. The system is secure as long as honest nodes collectively control more CPU power than any cooperating group of attacker nodes. 1 2. Transactions We define an electronic coin as a chain of digital signatures. Each owner transfers the coin to the next by digitally signing a hash of the previous transaction and the public key of the next owner and adding these to the end of the coin. A payee can verify the signatures to verify the chain of ownership. Transaction Hash Transaction Hash Transaction Hash Owner 1's Public Key Owner 2's Public Key Owner 3's Public Key Owner 0's Signature Owner 1's Signature The problem of course is the payee can't verify that one of the owners did not double-spend the coin. A common solution is to introduce a trusted central authority, or mint, that checks every transaction for double spending. After each transaction, the coin must be returned to the mint to issue a new coin, and only coins issued directly from the mint are trusted not to be double-spent. The problem with this solution is that the fate of the entire money system depends on the company running the mint, with every transaction having to go through them, just like a bank. We need a way for the payee to know that the previous owners did not sign any earlier transactions. For our purposes, the earliest transaction is the one that counts, so we don't care about later attempts to double-spend. The only way to confirm the absence of a transaction is to be aware of all transactions. In the mint based model, the mint was aware of all transactions and decided which arrived first. To accomplish this without a trusted party, transactions must be publicly announced [1], and we need a system for participants to agree on a single history of the order in which they were received. The payee needs proof that at the time of each transaction, the majority of nodes agreed it was the first received. 3. Timestamp Server The solution we propose begins with a timestamp server. A timestamp server works by taking a hash of a block of items to be timestamped and widely publishing the hash, such as in a newspaper or Usenet post [2-5]. The timestamp proves that the data must have existed at the time, obviously, in order to get into the hash. Each timestamp includes the previous timestamp in its hash, forming a chain, with each additional timestamp reinforcing the ones before it. Hash Hash Owner 2's Signature Owner 1's Private Key Owner 2's Private Key Owner 3's Private Key Block Item Item ... 2 Block Item Item ... Verify Verify Sign Sign 4. Proof-of-Work To implement a distributed timestamp server on a peer-to-peer basis, we will need to use a proof- of-work system similar to Adam Back's Hashcash [6], rather than newspaper or Usenet posts. The proof-of-work involves scanning for a value that when hashed, such as with SHA-256, the hash begins with a number of zero bits. The average work required is exponential in the number of zero bits required and can be verified by executing a single hash. For our timestamp network, we implement the proof-of-work by incrementing a nonce in the block until a value is found that gives the block's hash the required zero bits. Once the CPU effort has been expended to make it satisfy the proof-of-work, the block cannot be changed without redoing the work. As later blocks are chained after it, the work to change the block would include redoing all the blocks after it. The proof-of-work also solves the problem of determining representation in majority decision making. If the majority were based on one-IP-address-one-vote, it could be subverted by anyone able to allocate many IPs. Proof-of-work is essentially one-CPU-one-vote. The majority decision is represented by the longest chain, which has the greatest proof-of-work effort invested in it. If a majority of CPU power is controlled by honest nodes, the honest chain will grow the fastest and outpace any competing chains. To modify a past block, an attacker would have to redo the proof-of-work of the block and all blocks after it and then catch up with and surpass the work of the honest nodes. We will show later that the probability of a slower attacker catching up diminishes exponentially as subsequent blocks are added. To compensate for increasing hardware speed and varying interest in running nodes over time, the proof-of-work difficulty is determined by a moving average targeting an average number of blocks per hour. If they're generated too fast, the difficulty increases. 5. Network The steps to run the network are as follows: 1) New transactions are broadcast to all nodes. 2) Each node collects new transactions into a block. 3) Each node works on finding a difficult proof-of-work for its block. 4) When a node finds a proof-of-work, it broadcasts the block to all nodes. 5) Nodes accept the block only if all transactions in it are valid and not already spent. 6) Nodes express their acceptance of the block by working on creating the next block in the chain, using the hash of the accepted block as the previous hash. Nodes always consider the longest chain to be the correct one and will keep working on extending it. If two nodes broadcast different versions of the next block simultaneously, some nodes may receive one or the other first. In that case, they work on the first one they received, but save the other branch in case it becomes longer. The tie will be broken when the next proof- of-work is found and one branch becomes longer; the nodes that were working on the other branch will then switch to the longer one. 3 Block Nonce Tx Tx ... Block Nonce Tx Tx ... Prev Hash Prev Hash New transaction broadcasts do not necessarily need to reach all nodes. As long as they reach many nodes, they will get into a block before long. Block broadcasts are also tolerant of dropped messages. If a node does not receive a block, it will request it when it receives the next block and realizes it missed one. 6. Incentive By convention, the first transaction in a block is a special transaction that starts a new coin owned by the creator of the block. This adds an incentive for nodes to support the network, and provides a way to initially distribute coins into circulation, since there is no central authority to issue them. The steady addition of a constant of amount of new coins is analogous to gold miners expending resources to add gold to circulation. In our case, it is CPU time and electricity that is expended. The incentive can also be funded with transaction fees. If the output value of a transaction is less than its input value, the difference is a transaction fee that is added to the incentive value of the block containing the transaction. Once a predetermined number of coins have entered circulation, the incentive can transition entirely to transaction fees and be completely inflation free. The incentive may help encourage nodes to stay honest. If a greedy attacker is able to assemble more CPU power than all the honest nodes, he would have to choose between using it to defraud people by stealing back his payments, or using it to generate new coins. He ought to find it more profitable to play by the rules, such rules that favour him with more new coins than everyone else combined, than to undermine the system and the validity of his own wealth. 7. Reclaiming Disk Space Once the latest transaction in a coin is buried under enough blocks, the spent transactions before it can be discarded to save disk space. To facilitate this without breaking the block's hash, transactions are hashed in a Merkle Tree [7][2][5], with only the root included in the block's hash. Old blocks can then be compacted by stubbing off branches of the tree. The interior hashes do not need to be stored. Block Hash0 Hash1 Hash2 Hash3 Tx0 Tx1 Tx2 Tx3 Block Header (Block Hash) Prev Hash Nonce Root Hash Hash01 Hash23 Block Block Header (Block Hash) Prev Hash Nonce Root Hash Hash01 Hash23 Hash2 Hash3 Tx3 Transactions Hashed in a Merkle Tree After Pruning Tx0-2 from the Block A block header with no transactions would be about 80 bytes. If we suppose blocks are generated every 10 minutes, 80 bytes * 6 * 24 * 365 = 4.2MB per year. With computer systems typically selling with 2GB of RAM as of 2008, and Moore's Law predicting current growth of 1.2GB per year, storage should not be a problem even if the block headers must be kept in memory. 4 8. Simplified Payment Verification It is possible to verify payments without running a full network node. A user only needs to keep a copy of the block headers of the longest proof-of-work chain, which he can get by querying network nodes until he's convinced he has the longest chain, and obtain the Merkle branch linking the transaction to the block it's timestamped in. He can't check the transaction for himself, but by linking it to a place in the chain, he can see that a network node has accepted it, and blocks added after it further confirm the network has accepted it. Longest Proof-of-Work Chain Block Header Block Header Block Header Prev Hash Nonce Prev Hash Nonce Prev Hash Nonce Merkle Root Merkle Root Merkle Root Hash01 Hash23 Merkle Branch for Tx3 Hash2 Hash3 Tx3 As such, the verification is reliable as long as honest nodes control the network, but is more vulnerable if the network is overpowered by an attacker. While network nodes can verify transactions for themselves, the simplified method can be fooled by an attacker's fabricated transactions for as long as the attacker can continue to overpower the network. One strategy to protect against this would be to accept alerts from network nodes when they detect an invalid block, prompting the user's software to download the full block and alerted transactions to confirm the inconsistency. Businesses that receive frequent payments will probably still want to run their own nodes for more independent security and quicker verification. 9. Combining and Splitting Value Although it would be possible to handle coins individually, it would be unwieldy to make a separate transaction for every cent in a transfer. To allow value to be split and combined, transactions contain multiple inputs and outputs. Normally there will be either a single input from a larger previous transaction or multiple inputs combining smaller amounts, and at most two outputs: one for the payment, and one returning the change, if any, back to the sender. It should be noted that fan-out, where a transaction depends on several transactions, and those transactions depend on many more, is not a problem here. There is never the need to extract a complete standalone copy of a transaction's history. 5 Transaction In Out In ... ... 10. Privacy The traditional banking model achieves a level of privacy by limiting access to information to the parties involved and the trusted third party. The necessity to announce all transactions publicly precludes this method, but privacy can still be maintained by breaking the flow of information in another place: by keeping public keys anonymous. The public can see that someone is sending an amount to someone else, but without information linking the transaction to anyone. This is similar to the level of information released by stock exchanges, where the time and size of individual trades, the "tape", is made public, but without telling who the parties were. Traditional Privacy Model Identities Transactions New Privacy Model Identities Transactions As an additional firewall, a new key pair should be used for each transaction to keep them from being linked to a common owner. Some linking is still unavoidable with multi-input transactions, which necessarily reveal that their inputs were owned by the same owner. The risk is that if the owner of a key is revealed, linking could reveal other transactions that belonged to the same owner. 11. Calculations We consider the scenario of an attacker trying to generate an alternate chain faster than the honest chain. Even if this is accomplished, it does not throw the system open to arbitrary changes, such as creating value out of thin air or taking money that never belonged to the attacker. Nodes are not going to accept an invalid transaction as payment, and honest nodes will never accept a block containing them. An attacker can only try to change one of his own transactions to take back money he recently spent. The race between the honest chain and an attacker chain can be characterized as a Binomial Random Walk. The success event is the honest chain being extended by one block, increasing its lead by +1, and the failure event is the attacker's chain being extended by one block, reducing the gap by -1. The probability of an attacker catching up from a given deficit is analogous to a Gambler's Ruin problem. Suppose a gambler with unlimited credit starts at a deficit and plays potentially an infinite number of trials to try to reach breakeven. We can calculate the probability he ever reaches breakeven, or that an attacker ever catches up with the honest chain, as follows [8]: p = probability an honest node finds the next block q = probability the attacker finds the next block qz = probability the attacker will ever catch up from z blocks behind Trusted Third Party q ={ 1 if p≤q} z q/pz if pq 6 Counterparty Public Public Given our assumption that p > q, the probability drops exponentially as the number of blocks the attacker has to catch up with increases. With the odds against him, if he doesn't make a lucky lunge forward early on, his chances become vanishingly small as he falls further behind. We now consider how long the recipient of a new transaction needs to wait before being sufficiently certain the sender can't change the transaction. We assume the sender is an attacker who wants to make the recipient believe he paid him for a while, then switch it to pay back to himself after some time has passed. The receiver will be alerted when that happens, but the sender hopes it will be too late. The receiver generates a new key pair and gives the public key to the sender shortly before signing. This prevents the sender from preparing a chain of blocks ahead of time by working on it continuously until he is lucky enough to get far enough ahead, then executing the transaction at that moment. Once the transaction is sent, the dishonest sender starts working in secret on a parallel chain containing an alternate version of his transaction. The recipient waits until the transaction has been added to a block and z blocks have been linked after it. He doesn't know the exact amount of progress the attacker has made, but assuming the honest blocks took the average expected time per block, the attacker's potential progress will be a Poisson distribution with expected value: = z qp To get the probability the attacker could still catch up now, we multiply the Poisson density for each amount of progress he could have made by the probability he could catch up from that point: ∞ ke−{q/pz−k ifk≤z} ∑k=0 k!⋅ 1 ifkz Rearranging to avoid summing the infinite tail of the distribution... z ke− z−k 1−∑k=0 k! 1−q/p Converting to C code... #include <math.h> double AttackerSuccessProbability(double q, int z) { double p = 1.0 - q; double lambda = z * (q / p); double sum = 1.0; int i, k; for (k = 0; k <= z; k++) { double poisson = exp(-lambda); for (i = 1; i <= k; i++) poisson *= lambda / i; sum -= poisson * (1 - pow(q / p, z - k)); } return sum; } 7 Running some results, we can see the probability drop off exponentially with z. q=0.1 z=0 P=1.0000000 z=1 P=0.2045873 z=2 P=0.0509779 z=3 P=0.0131722 z=4 P=0.0034552 z=5 P=0.0009137 z=6 P=0.0002428 z=7 P=0.0000647 z=8 P=0.0000173 z=9 P=0.0000046 z=10 P=0.0000012 q=0.3 z=0 P=1.0000000 z=5 P=0.1773523 z=10 P=0.0416605 z=15 P=0.0101008 z=20 P=0.0024804 z=25 P=0.0006132 z=30 P=0.0001522 z=35 P=0.0000379 z=40 P=0.0000095 z=45 P=0.0000024 z=50 P=0.0000006 Solving for P less than 0.1%... P < 0.001 q=0.10 z=5 q=0.15 z=8 q=0.20 z=11 q=0.25 z=15 q=0.30 z=24 q=0.35 z=41 q=0.40 z=89 q=0.45 z=340 12. Conclusion We have proposed a system for electronic transactions without relying on trust. We started with the usual framework of coins made from digital signatures, which provides strong control of ownership, but is incomplete without a way to prevent double-spending. To solve this, we proposed a peer-to-peer network using proof-of-work to record a public history of transactions that quickly becomes computationally impractical for an attacker to change if honest nodes control a majority of CPU power. The network is robust in its unstructured simplicity. Nodes work all at once with little coordination. They do not need to be identified, since messages are not routed to any particular place and only need to be delivered on a best effort basis. Nodes can leave and rejoin the network at will, accepting the proof-of-work chain as proof of what happened while they were gone. They vote with their CPU power, expressing their acceptance of valid blocks by working on extending them and rejecting invalid blocks by refusing to work on them. Any needed rules and incentives can be enforced with this consensus mechanism. 8 References [1] W. Dai, "b-money," http://www.weidai.com/bmoney.txt, 1998. [2] H. Massias, X.S. Avila, and J.-J. Quisquater, "Design of a secure timestamping service with minimal trust requirements," In 20th Symposium on Information Theory in the Benelux, May 1999. [3] S. Haber, W.S. Stornetta, "How to time-stamp a digital document," In Journal of Cryptology, vol 3, no 2, pages 99-111, 1991. [4] D. Bayer, S. Haber, W.S. Stornetta, "Improving the efficiency and reliability of digital time-stamping," In Sequences II: Methods in Communication, Security and Computer Science, pages 329-334, 1993. [5] S. Haber, W.S. Stornetta, "Secure names for bit-strings," In Proceedings of the 4th ACM Conference on Computer and Communications Security, pages 28-35, April 1997. [6] A. Back, "Hashcash - a denial of service counter-measure," http://www.hashcash.org/papers/hashcash.pdf, 2002. [7] R.C. Merkle, "Protocols for public key cryptosystems," In Proc. 1980 Symposium on Security and Privacy, IEEE Computer Society, pages 122-133, April 1980. [8] W. Feller, "An introduction to probability theory and its applications," 1957. 9
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