Maskify - Sensitive Data Masking Library

Maskify is a lightweight, efficient, and flexible library designed to help developers securely mask sensitive data, such as Brazilian documents (CPF, CNPJ), emails, credit cards, mobile and residential phone numbers, and more. It provides out-of-the-box masking for common data types and customizable options for other sensitive information, ensuring compliance with data protection regulations like LGPD and GDPR.

✅ Fully compliant with the new Brazilian CNPJ law! Maskify.Core already supports the new alphanumeric CNPJ format (Instrução Normativa RFB nº 2.229/2024), which allows letters and numbers in CNPJ starting January 2026.

Key Features

• RG Masking: Masks Brazilian RG numbers (7 to 9 digits), keeping only the last two digits visible.
• CPF Masking: Effortlessly masks CPF numbers, both formatted and unformatted.
• CNPJ Masking: Supports both numeric and alphanumeric CNPJ formats, compliant with Brazilian regulations.
• Email Masking: Partially hides email addresses while preserving the domain.
• Credit Card Masking: Safely masks credit card numbers, including support for:
  • Standard 16-digit cards.
  • American Express (15 digits).
  • Diners Club (14 digits).
• Mobile Phone Masking: Masks Brazilian mobile phone numbers (9 digits), keeping the area code (DDD) and the last 4 digits visible.
• Residential Phone Masking: Masks landline phone numbers (8 digits), with the area code (DDD) and the last 4 digits visible.
• Generic Masking Method: Enables masking of any sensitive data (e.g., custom fields) with full control over visible characters and the masking character.
• Customizable Masking: Allows specifying the number of visible characters and choosing the masking character (e.g., *, #).
• License Plate Masking: Masks Brazilian license plates (old and Mercosul formats).

Installation

Install Maskify via NuGet Package Manager:

dotnet add package Maskify.Core

For more details, visit the NuGet page.

Usage Guide

1. Mask CPF

Easily mask Brazilian CPF numbers, whether formatted or not:

using Maskify.Core;

string cpf = "123.456.789-10";
string maskedCpf = Masker.MaskCPF(cpf);
Console.WriteLine(maskedCpf); // Output: ***.***.***-10

2. Mask RG

Mask Brazilian RG numbers (7 to 9 digits), formatted or unformatted:

using Maskify.Core;

// RG formatado
string rgFormatted = "46.546.987-3";
string maskedRgFormatted = Masker.MaskRG(rgFormatted);
Console.WriteLine(maskedRgFormatted); // Output: **.***.***-3

// RG não formatado
string rgUnformatted = "465469873";
string maskedRgUnformatted = Masker.MaskRG(rgUnformatted);
Console.WriteLine(maskedRgUnformatted); // Output: *******3

// RG com 7 dígitos
string rgShort = "1234567";
string maskedRgShort = Masker.MaskRG(rgShort);
Console.WriteLine(maskedRgShort); // Output: *****67

3. Mask CNPJ

Mask CNPJ numbers with support for formatted and unformatted inputs:

using Maskify.Core;

string cnpj = "12.345.678/0001-99";
string maskedCnpj = Masker.MaskCNPJ(cnpj);
Console.WriteLine(maskedCnpj); // Output: **.***.***/0001-99

4. Mask Email

Hide part of the email address while preserving the domain:

using Maskify.Core;

string email = "user@example.com";
string maskedEmail = Masker.MaskEmail(email);
Console.WriteLine(maskedEmail); // Output: use****@example.com

5. Mask Credit Cards

Supports masking of credit card numbers (standard, Amex, and Diners Club):

using Maskify.Core;

// Masking a standard 16-digit card
string maskedCreditCard = "1234 5678 9012 3456".MaskCreditCard();
Console.WriteLine(maskedCreditCard); // Output: "**** **** **** 3456"

// Masking an American Express card (15 digits)
string maskedAmex = "3782 822463 10005".MaskCreditCard('#');
Console.WriteLine(maskedAmex); // Output: "#### ###### #0005"

// Masking a Diners Club card (14 digits)
string maskedDinersClub = "3056 9304 5567 89".MaskCreditCard();
Console.WriteLine(maskedDinersClub); // Output: "**** **** **67 89"

6. Mask Mobile Phone

Mask Brazilian mobile phone numbers (9 digits) while keeping the DDD and the last 4 digits visible:

using Maskify.Core;

string mobilePhone = "(11) 91234-5678";
string maskedMobilePhone = mobilePhone.MaskMobilePhone();
Console.WriteLine(maskedMobilePhone); // Output: (11) 9****-5678

7. Mask Residential Phone

Mask Brazilian landline phone numbers (8 digits), maintaining the DDD and the last 4 digits visible:

using Maskify.Core;

string residentialPhone = "(11) 2345-6789";
string maskedResidentialPhone = residentialPhone.MaskResidentialPhone();
Console.WriteLine(maskedResidentialPhone); // Output: (11) ****-6789

8. Mask Custom Data

Use the generic method to mask any sensitive data:

using Maskify.Core;

string sensitiveData = "Sensitive Info";
string maskedData = Masker.Mask(sensitiveData, 3, 4, '*');
Console.WriteLine(maskedData); // Output: Sen***********Info

Parameters:

• startPosition: Number of visible characters at the beginning.
• length: Number of characters to mask.
• char: Masking character (e.g., *, #).

9. MaskSensitiveData DataAnnotation

Use DataAnnotations to mask sensitive data directly in your model classes, such as CPF, CNPJ, credit card numbers, emails, and phone numbers:

using Maskify.Core.Annotations;

public class Customer
{
    [MaskSensitiveData(MaskSensitiveDataAttribute.DataType.RG, MaskCharacter = '*', ErrorMessage = "Invalid RG.")]
    public string RG { get; set; }

    [MaskSensitiveData(MaskSensitiveDataAttribute.DataType.CPF, MaskCharacter = '#', ErrorMessage = "Invalid CPF.")]
    public string CPF { get; set; }

    [MaskSensitiveData(MaskSensitiveDataAttribute.DataType.CNPJ, MaskCharacter = '*', ErrorMessage = "Invalid CNPJ.")]
    public string CNPJ { get; set; }

    [MaskSensitiveData(MaskSensitiveDataAttribute.DataType.CreditCard, MaskCharacter = '*', ErrorMessage = "Invalid credit card.")]
    public string CreditCard { get; set; }

    [MaskSensitiveData(MaskSensitiveDataAttribute.DataType.Email, MaskCharacter = '*', ErrorMessage = "Invalid email.")]
    public string Email { get; set; }

    [MaskSensitiveData(MaskSensitiveDataAttribute.DataType.ResidentialPhone, MaskCharacter = '*', ErrorMessage = "Invalid phone number.")]
    public string ResidentialPhone { get; set; }

    [MaskSensitiveData(MaskSensitiveDataAttribute.DataType.MobilePhone, MaskCharacter = '*', ErrorMessage = "Invalid mobile number.")]
    public string MobilePhone { get; set; }

    [MaskSensitiveData(MaskSensitiveDataAttribute.DataType.VehicleLicensePlate, MaskCharacter = '#', ErrorMessage = "Invalid vehicle license plate.")]
    public string VehicleLicensePlate { get; set; }

}

10. Mask License Plate

Mask Brazilian license plates (old and Mercosul formats), showing only the first 3 characters:

using Maskify.Core;

string licensePlate = "BRA2E19";
string maskedLicensePlate = Masker.MaskLicensePlate(licensePlate);
Console.WriteLine(maskedLicensePlate); // Output: BRA****

Custom Masking Rules

Create custom masking rules with the MaskSensitiveData attribute, specifying the number of visible characters and the masking character.

Contributing

Contributions are welcome! Feel free to submit a pull request or open an issue on our GitHub repository.

License

This project is licensed under the MIT License.