public static byte[] EncryptIGE(byte[] originPlaintext, byte[] key, byte[] iv)
{
var plaintext = originPlaintext
.Concat(Helpers.GenerateRandomBytes(Helpers.PositiveMod(-originPlaintext.Length, 16)))
.ToArray();
var iv1 = new byte[iv.Length / 2];
var iv2 = new byte[iv.Length / 2];
Array.Copy(iv, 0, iv1, 0, iv1.Length);
Array.Copy(iv, iv1.Length, iv2, 0, iv2.Length);
var aes = new AesEngine();
aes.Init(true, key);
var blocksCount = plaintext.Length / 16;
var ciphertext = new byte[plaintext.Length];
var ciphertextBlock = new byte[16];
var plaintextBlock = new byte[16];
for (int blockIndex = 0; blockIndex < blocksCount; blockIndex++)
{
Array.Copy(plaintext, 16 * blockIndex, plaintextBlock, 0, 16);
for (int i = 0; i < 16; i++)
{
plaintextBlock[i] ^= iv1[i];
}
aes.ProcessBlock(plaintextBlock, 0, ciphertextBlock, 0);
for (int i = 0; i < 16; i++)
{
ciphertextBlock[i] ^= iv2[i];
}
Array.Copy(ciphertextBlock, 0, iv1, 0, 16);
Array.Copy(plaintext, 16 * blockIndex, iv2, 0, 16);
Array.Copy(ciphertextBlock, 0, ciphertext, blockIndex * 16, 16);
}
return(ciphertext);
}
public static byte[] DecryptIGE(byte[] ciphertext, byte[] key, byte[] iv)
{
var iv1 = new byte[iv.Length / 2];
var iv2 = new byte[iv.Length / 2];
Array.Copy(iv, 0, iv1, 0, iv1.Length);
Array.Copy(iv, iv1.Length, iv2, 0, iv2.Length);
var aes = new AesEngine();
aes.Init(false, key);
var plaintext = new byte[ciphertext.Length];
var blocksCount = ciphertext.Length / 16;
var ciphertextBlock = new byte[16];
var plaintextBlock = new byte[16];
for (var blockIndex = 0; blockIndex < blocksCount; blockIndex++)
{
for (var i = 0; i < 16; i++)
{
ciphertextBlock[i] = (byte)(ciphertext[blockIndex * 16 + i] ^ iv2[i]);
}
aes.ProcessBlock(ciphertextBlock, 0, plaintextBlock, 0);
for (var i = 0; i < 16; i++)
{
plaintextBlock[i] ^= iv1[i];
}
Array.Copy(ciphertext, blockIndex * 16, iv1, 0, 16);
Array.Copy(plaintextBlock, 0, iv2, 0, 16);
Array.Copy(plaintextBlock, 0, plaintext, blockIndex * 16, 16);
}
return(plaintext);
}