Rijndael (/AES)
AES (or Rijndael) is the new replacement for DES, and uses 128-bit blocks with 128, 192 and 256 bit encryption keys. It was selected by NIST in 2001 (after a five year standardisation process). The name Rijndael comes from its Belgium creators: Joan Daemen and Vincent Rijmen. The key has an IV and a key element, where the IV gives the overall key some variation. In this case the key is 256 bits, and the IV is 128 bits.
Encrypted stream:
and to test, the decrypted text is:
In this case, if we try "test" as the key, and test message of: "This is a test message" which should get:
54A6B8A846B61EFBFD258AF2B1E7BF129A24545CAEDC315DA1D3F924E4AA2F00
Also, a key of "test" with a message of "test" gives:
AECC52950EFC49F6B2B2407ECEE65FE5
which is 32 characters, and thus relates to 128 bits, which is the block size (as "test" fits into a single block). All our outputs will thus be a multiple of 32 hex characters.
The code is:
try
{
Rijndael myRijndael = new RijndaelManaged();
myRijndael.Key = StringToByte(this.tbKey.Text, 32); // convert to 32 characters - 256 bits
myRijndael.IV = StringToByte(" "); // 16 characters for IV
byte[] key = myRijndael.Key;
byte[] IV = myRijndael.IV;
ICryptoTransform encryptor = myRijndael.CreateEncryptor(key, IV);
MemoryStream msEncrypt = new MemoryStream();
CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write);
// Write all data to the crypto stream and flush it.
csEncrypt.Write(StringToByte(this.tbMessage.Text), 0, StringToByte(this.tbMessage.Text).Length);
csEncrypt.FlushFinalBlock();
// Get the encrypted array of bytes.
byte[] encrypted = msEncrypt.ToArray();
this.tbEncrypt.Text = ByteToString(encrypted);
ICryptoTransform decryptor = myRijndael.CreateDecryptor(key, IV);
// Now decrypt the previously encrypted message using the decryptor
MemoryStream msDecrypt = new MemoryStream(encrypted);
CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read);
this.tbDecrypt.Text = ByteToString(csDecrypt);
}
catch (Exception ex)
{
this.tbEncrypt.Text = ex.Message.ToString();
}
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