Chilkat.Crypt2 crypt = new Chilkat.Crypt2();

bool success = crypt.UnlockComponent("Anything for 30-day trial");
if (success != true) {
    Console.WriteLine(crypt.LastErrorText);
    return;
}

//  AES is also known as Rijndael.
crypt.CryptAlgorithm = "aes";

//  CipherMode may be "ecb", "cbc", "ofb", "cfb", "gcm", etc.
//  Note: Check the online reference documentation to see the Chilkat versions
//  when certain cipher modes were introduced.
crypt.CipherMode = "cbc";

//  KeyLength may be 128, 192, 256
crypt.KeyLength = 256;

//  The padding scheme determines the contents of the bytes
//  that are added to pad the result to a multiple of the
//  encryption algorithm's block size.  AES has a block
//  size of 16 bytes, so encrypted output is always
//  a multiple of 16.
crypt.PaddingScheme = 0;

//  EncodingMode specifies the encoding of the output for
//  encryption, and the input for decryption.
//  It may be "hex", "url", "base64", or "quoted-printable".
crypt.EncodingMode = "hex";

//  An initialization vector is required if using CBC mode.
//  ECB mode does not use an IV.
//  The length of the IV is equal to the algorithm's block size.
//  It is NOT equal to the length of the key.
string ivHex = "000102030405060708090A0B0C0D0E0F";
crypt.SetEncodedIV(ivHex,"hex");

//  The secret key must equal the size of the key.  For
//  256-bit encryption, the binary secret key is 32 bytes.
//  For 128-bit encryption, the binary secret key is 16 bytes.
string keyHex = "000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F";
crypt.SetEncodedKey(keyHex,"hex");

//  Encrypt a string...
//  The input string is 44 ANSI characters (i.e. 44 bytes), so
//  the output should be 48 bytes (a multiple of 16).
//  Because the output is a hex string, it should
//  be 96 characters long (2 chars per byte).
string encStr = crypt.EncryptStringENC("The quick brown fox jumps over the lazy dog.");
Console.WriteLine(encStr);

//  Now decrypt:
string decStr = crypt.DecryptStringENC(encStr);
Console.WriteLine(decStr);