AES (American Encryption Standard) is a quite new block cipher,
specified by NIST as a replacement for the older DES standard. The
standard is the result of a competition between cipher designers.
The winning design, also known as RIJNDAEL, was constructed by
Joan Daemen and Vincent Rijnmen.
Like all the AES candidates, the winning design uses a block size
of 128 bits, or 16 octets, and variable key-size, 128, 192 and 256
bits (16, 24 and 32 octets) being the allowed key sizes. It does
not have any weak keys.
Crypto.Substitution()->set_rot_key()