# advanced encryption standard (DES) (AES)

The National Institute of Standards and Technology(NIST) has been developing the Advanced Encryption Standard( AES) in collaboration with industrial companies for years. This symmetric encryption is intended to replace DES encryption.

AES encryption specifies three different key lengths of 128, 192 and 256 bits. This means in the case of the 128 bit long key `3.4 * 10^38` possibilities, with the 192 bit long key there are `6.2 * 10^57` possibilities and with the 256 bit key even `1.1 * 10^77` possibilities. For comparison, the 56 bit long DES key offers `7.2 * 10^16` possibilities.

The goal of the NIST activities is to develop a FIPS standard, Federal Information Processing Standard, in which an encryption algorithm is specified, with which sensitive data can be protected against unauthorized access and which has a future security.

In 1997, NIST had launched the Advanced Encryption Standard (AES) initiative and announced its terms for the algorithm. Of the proposed encryption algorithms, NIST shortlisted five algorithms; namely, MARS, RC6, Rijndael, Serpent, and Twofish. In October 2000, Rijndael was chosen as the encryption algorithm.