The digest package provides a function 'digest()' for the creation
of hash digests of arbitrary R objects (using the md5, sha-1, sha-256
and crc32 algorithms) permitting easy comparison of R language
objects, as well as a function 'hmac()' to create hash-based message
authentication code. The md5 algorithm by Ron Rivest is specified
in RFC 1321, the sha-1 and sha-256 algorithms are specified in
FIPS-180-1 and FIPS-180-2, and the crc32 algorithm is described in
ftp://ftp.rocksoft.com/cliens/rocksoft/papers/crc_v3.txt. For md5,
sha-1, sha-256 and aes, this package uses a small standalone
implementations that were provided by Christophe Devine. For crc32,
code from the zlib library is used. For sha-512, an implementation
by Aaron D. Gifford is used. Please note that this package is not
meant to be deployed for cryptographic purposes for which more
comprehensive (and widely tested) libraries such as OpenSSL should
be used.

WWW: http://cran.r-project.org/web/packages/digest/