Rijndael is a symmetric block cipher supporting block and key sizes of 128, 192 and 256 bits. It has been chosen as the AES cipher. [Edit]

See Also: Rijndael Members

System.Object
     System.Security.Cryptography.SymmetricAlgorithm
          System.Security.Cryptography.Rijndael

[System.Runtime.InteropServices.ComVisible(true)] public abstract class Rijndael : SymmetricAlgorithm

Remarks

To be compatible with AES you should only use 128 bits as the block size. Other block size (192, 256) aren't part of the AES specification and may be problematic for interoperability with other implementations.

The AES specification is known as NIST FIPS PUB 197: Advanced Encryption Standard available at http://csrc.nist.gov/publications/fips/fips197/fips-197.pdf

[Edit]

Requirements

Namespace: System.Security.Cryptography
Assembly: mscorlib (in mscorlib.dll)
Assembly Versions: 1.0.5000.0, 2.0.0.0