`The US standard for symmetric cryptography, in which the same key is
used for both encryption and decryption is the Data Encryption
Standard (DES). This is based upon a combination and permutation of
shifts and xors and so can be very fast when implemented directly on
hardware (1 GByte/s throughput or better) or on general purpose
processors. The current key size of 56 bits (plus 8 parity bits) is
now starting to seem small, but the use of larger keys with triple DES can
generate much greater security. Since the implementation of DES is
fast, it can easily be pipelined with software codecs and not impact
the performance.
`

`IDEA is an alternative and stronger form of symmetric block
encryption. Its security is based upon combining xors with addition
and multiplication in modulo 16 arithmetic. This is also fast on
general purpose processors and is comparable in speed to DES
implementations. The major advantage of IDEA is that the keys are 128
bits and thus much stronger (a.k.a. harder to break) than standard 56 bit DES.
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