zmsg

A zero knowledge messaging system built on zcash.

zmsg uses the encrypted memo field of zcash sheilded transactions to send messages to other parties. The sent messages get stored in the zcash blockchain and the recipient can check for messages at any time (no need to be online at the same time). Since the messages get stored in the blockchain, they are on every full zcash node. The implication here is that its not possible to tell who the target of any given message is.

Currently, each message sends 0.0001 ZEC. You can change this value by setting the --txval flag on sendmsg.

Installation

First, make sure you have go installed, then:

go get github.com/whyrusleeping/zmsg

Usage

Note: To use zmsg, you'll need a running zcash daemon, a z_address, and some spare ZEC in that address.

sendmsg

To send a message, use zmsg sendmsg:

$ export TARGET_ZADDR=zchfvC6iubfsAxaNrbM4kkGDSpwjafECjqQ1BZBFXtotXyXARz2NoYRVEyfLEKGCFRY7Xfj2Q3jFueoHHmQKb63C3zumYnU
$ zmsg sendmsg -to=$TARGET_ZADDR "Hello zmsg! welcome to pretty secure messaging"
message: "Hello zmsg! welcome to pretty secure messaging"
sending message from <your z_addr>
sending message...
Message sent successfuly!
message sent! (txid = <transaction id>)

Note that this will take about a minute to compute the zero-knowledge proof, and another few minutes before the transaction gets propagated and confirmed for the other side to see it.

check

To check for messages, run zmsg check:

================================================================================
> Got 2 messages.
================================================================================
| Message #0 (val = 0.000010)
| To: zchfvC6iubfsAxaNrbM4kkGDSpwjafECjqQ1BZBFXtotXyXARz2NoYRVEyfLEKGCFRY7Xfj2Q3jFueoHHmQKb63C3zumYnU
| Date: 2016-11-11 17:36:31 -0800 PST
|
|  This is a test of zmsg, hello everyone!
================================================================================
| Message #1 (val = 0.000010)
| To: zchfvC6iubfsAxaNrbM4kkGDSpwjafECjqQ1BZBFXtotXyXARz2NoYRVEyfLEKGCFRY7Xfj2Q3jFueoHHmQKb63C3zumYnU
| Date: 2016-11-11 17:44:44 -0800 PST
|
|  This is message number 'two', i'm sitting in a coffee shop. Don't tell anyone.
================================================================================

Send me a message!

If you're trying this out and want to say hi, send me a message at zchfvC6iubfsAxaNrbM4kkGDSpwjafECjqQ1BZBFXtotXyXARz2NoYRVEyfLEKGCFRY7Xfj2Q3jFueoHHmQKb63C3zumYnU.

License

MIT, whyrusleeping