The [sha1] secure hash algorithm produces a digest of 160 bits. This provides 80 bits of security against collisions
given the birthday attack (ref). An update document from NIST [http://csrc.nist.gov/cryptval/shs/sha256-384-512.pdf]
specifies a new family of secure hashing algorithms with longer digest lengths, specifically 
SHA-256, SHA-384, and SHA-512. An additional update also specifies SHA-224 [http://csrc.nist.gov/publications/fips/fips180-2/fips180-2withchangenotice.pdf].

[tcllib] now includes a pure-tcl implementation of SHA-224 and SHA-256. For comparison, here are some timing
data for the pure-Tcl implementation of all the digests in [tcllib]

   1 md4    time:  190 microseconds per iteration
   1 md5    time:  236 microseconds per iteration
   1 rmd128 time:  337 microseconds per iteration
   1 rmd160 time:  525 microseconds per iteration
   1 sha1   time:  826 microseconds per iteration
   1 sha224 time: 1117 microseconds per iteration
   1 sha256 time: 1126 microseconds per iteration

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See also [sha1], [md4], [md5], [ripemd], [cryptkit]

[[ [Category Package], subset [Tcllib] | [Category Cryptography] ]]