The Data Encryption Standard (DES) was introduced in 19xx and
is formally defined in
FIPS 46-3
Using a 56-bit key (usually entered as a 64-bit value with odd parity bits),
working on a 64-bit data block.
There are several modes for using DES to encrypt blocks of data
that may be more (or less) than 8 bytes in size. Click here
for more details on how DES works.
The 56-bit key used by DES is no longer sufficient for good security, but
many applications use triple-DES
(encrypt using key part A, decrypt using key part B, encrypt using key part A)
to acheive a 112-bit key while maintaining compatibility with
plain DES (using key part A = key part B).