Symmetric algorithms are
algorithms for
cryptography that use the same
key to encrypt and decrypt the message. They can be divided into [stream ciphers]
? and
block ciphers. The former encrypts the bits of the message one at a time, while the latter takes a number of bits and encrypts them as a a single unit. Blocks of 64 bits have been common; the
Advanced Encryption Standard algorithm approved by
NIST in December
2001 uses 128 bit blocks. Symmetric algorithms are generally much faster to execute electronically than
asymmetric algorithms.