digest::hmac(3) [centos man page]

Digest::HMAC(3) 					User Contributed Perl Documentation					   Digest::HMAC(3)

NAME

       Digest::HMAC - Keyed-Hashing for Message Authentication

SYNOPSIS

	# Functional style
	use Digest::HMAC qw(hmac hmac_hex);
	$digest = hmac($data, $key, &myhash);
	print hmac_hex($data, $key, &myhash);

	# OO style
	use Digest::HMAC;
	$hmac = Digest::HMAC->new($key, "Digest::MyHash");

	$hmac->add($data);
	$hmac->addfile(*FILE);

	$digest = $hmac->digest;
	$digest = $hmac->hexdigest;
	$digest = $hmac->b64digest;

DESCRIPTION

       HMAC is used for message integrity checks between two parties that share a secret key, and works in combination with some other Digest
       algorithm, usually MD5 or SHA-1.  The HMAC mechanism is described in RFC 2104.

       HMAC follow the common "Digest::" interface, but the constructor takes the secret key and the name of some other simple "Digest::" as
       argument.

       The hmac() and hmac_hex() functions and the Digest::HMAC->new() constructor takes an optional $blocksize argument as well.  The HMAC
       algorithm assumes the digester to hash by iterating a basic compression function on blocks of data and the $blocksize should match the
       byte-length of such blocks.

       The default $blocksize is 64 which is suitable for the MD5 and SHA-1 digest functions.  For stronger algorithms the blocksize probably
       needs to be increased.

SEE ALSO

       Digest::HMAC_MD5, Digest::HMAC_SHA1

       RFC 2104

AUTHORS

       Graham Barr <gbarr@ti.com>, Gisle Aas <gisle@aas.no>

perl v5.16.3							    2011-07-25							   Digest::HMAC(3)

ISC-HMAC-FIXUP(1)						       BIND9							 ISC-HMAC-FIXUP(1)

NAME

       isc-hmac-fixup - fixes HMAC keys generated by older versions of BIND

SYNOPSIS

       isc-hmac-fixup {algorithm} {secret}

DESCRIPTION

       Versions of BIND 9 up to and including BIND 9.6 had a bug causing HMAC-SHA* TSIG keys which were longer than the digest length of the hash
       algorithm (i.e., SHA1 keys longer than 160 bits, SHA256 keys longer than 256 bits, etc) to be used incorrectly, generating a message
       authentication code that was incompatible with other DNS implementations.

       This bug has been fixed in BIND 9.7. However, the fix may cause incompatibility between older and newer versions of BIND, when using long
       keys.  isc-hmac-fixup modifies those keys to restore compatibility.

       To modify a key, run isc-hmac-fixup and specify the key's algorithm and secret on the command line. If the secret is longer than the digest
       length of the algorithm (64 bytes for SHA1 through SHA256, or 128 bytes for SHA384 and SHA512), then a new secret will be generated
       consisting of a hash digest of the old secret. (If the secret did not require conversion, then it will be printed without modification.)

SECURITY CONSIDERATIONS

       Secrets that have been converted by isc-hmac-fixup are shortened, but as this is how the HMAC protocol works in operation anyway, it does
       not affect security. RFC 2104 notes, "Keys longer than [the digest length] are acceptable but the extra length would not significantly
       increase the function strength."

SEE ALSO

       BIND 9 Administrator Reference Manual, RFC 2104.

AUTHOR

       Internet Systems Consortium

COPYRIGHT

       Copyright (C) 2010 Internet Systems Consortium, Inc. ("ISC")

BIND9								  January 5, 2010						 ISC-HMAC-FIXUP(1)