DESCRIPTION

  Here is a implementation of crypto hashes for PostgreSQL.
  It exports 2 functions to SQL level:

    digest(data::text, hash_name::text)
	which returns hexadecimal coded hash over data by
	specified algorithm. eg

	> select digest('blah', 'sha1');
	5bf1fd927dfb8679496a2e6cf00cbe50c1c87145

    digest_exists(hash_name::text)::bool
	which reports if particular hash type exists.

  If any of arguments are NULL they return NULL.

HASHES

  For choosing library you must edit Makefile.

  standalone (default):
	MD5, SHA1

	(the code is from KAME project.  Actually I hate code
	duplication, but I also want to quarantee that MD5 and
	SHA1 exist)

  mhash (0.8.1):
	MD5, SHA1, CRC32, CRC32B, GOST, TIGER, RIPEMD160,
	HAVAL(256,224,192,160,128)

  openssl:
	MD5, SHA1, RIPEMD160, MD2

  kerberos5 (heimdal):
	MD5, SHA1