Rijndael encryption is an encryption algorithm upon which AES (advanced encryption standard) is based. "Rijndael" is a portmanteau of the names of Joan Daemen and Vincent Rijmen, the inventors of the algorithm.
Rijndael uses a design principle known as a substitution-permutation network, or an SP-network, to encrypt plaintext data. It uses a series of mathematical operations; decryption is performed by reversing the process. It has a relatively simple algebraic description, and runs very efficiently on both hardware and software implementations.