README.md

Rijndael256

AES cryptographic library for .NET Framework and .NET Core

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About

Rijndael256 makes encrypting data and files a breeze with the AES symmetric-key cipher Rijndael.

Features

• Advanced Encryption Standard (AES)
• Rijndael symmetric-key cipher:
  • Encrypt data or files
  • AES key sizes:
    • 128-bit
    • 192-bit
    • 256-bit
  • CBC Mode
• Authenticated Encryption (AE)
  • Encrypt-then-MAC (EtM)
• Cryptographic hashes:
  • SHA-512
  • PBKDF2

Quick Start

Encrypt a string using Rijndael AES 256-bit

string password = "sKzvYk#1Pn33!YN";  // The password to encrypt the data with
string plaintext = "Top secret data"; // The string to encrypt

// Encrypt the string
string ciphertext = Rijndael.Encrypt(plaintext, password, KeySize.Aes256);

// Decrypt the string
plaintext = Rijndael.Decrypt(ciphertext, password, KeySize.Aes256);

Encrypt a string using Authenticated Encryption (AE)

string password = "KQpc@HuQ66b$z37";  // The password to encrypt the data with
string plaintext = "Top secret data"; // The string to encrypt

// Encrypt the string
string aeCiphertext = RijndaelEtM.Encrypt(plaintext, password, KeySize.Aes256);

// Decrypt the string
plaintext = RijndaelEtM.Decrypt(aeCiphertext, password, KeySize.Aes256);

Encrypt a file using Rijndael AES 256-bit

string password = "2zj9cV!50BwJ$A1";            // The password to encrypt the file with
string plaintextFile = @"C:\TopSecretFile.png"; // The file to encrypt
string ciphertextFile = @"C:\SecureFile";       // The encrypted file (extension unnecessary)

// Encrypt the file
Rijndael.Encrypt(plaintextFile, ciphertextFile, password, KeySize.Aes256);

// Decrypt the file
Rijndael.Decrypt(ciphertextFile, plaintextFile, password, KeySize.Aes256);

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Settings

The Settings object is a collection of mutable defaults used throughout the library. Modification of these defaults is not necessary, but is made available for developers who want finer control of Rijndael256.

Setting	Description	Default
HashIterations	The number of iterations used to derive hashes	10000

Example

// The HashIterations setting is used in several places throughout the lib,
// with Rijndael.Encrypt being just one of them. After making this change,
// any future calls to Rijndael.Encrypt will make use of this new value
Settings.HashIterations = 25000;

// To reset all the settings to their default values
Settings.Reset();

Appendix

Authenticated Encryption (AE)

AE adds an integrity check to the resulting ciphertext, so we can authenticate the ciphertext before decrypting it. Whereas encryption provides confidentiality, AE adds authenticity.

Encrypt-then-MAC (EtM)

Rijndael256 offers AE via the EtM encryption mode, which was standardized in ISO/IEC 19772:2009.

EtM Workflow

1. Encryption:
   1. The plaintext is encrypted.
   2. A MAC is calculated from the resulting ciphertext.
   3. The MAC is appended to the ciphertext.
2. Decryption:
   1. The MAC is extracted from the ciphertext (M_o).
   2. A MAC is calculated from the ciphertext (M_n).
   3. The MACs are compared for equality (M_o == M_n)
      1. Equal: The ciphertext is decrypted.
      2. Not Equal: Authentication has failed -- the decryption process is aborted, with no attempt being made to decrypt the unauthentic ciphertext.