Provided by: libauthen-passphrase-perl_0.008-3_all 
NAME
Authen::Passphrase::SaltedDigest - passphrases using the generic salted digest algorithm
SYNOPSIS
use Authen::Passphrase::SaltedDigest;
$ppr = Authen::Passphrase::SaltedDigest->new(
algorithm => "SHA-1",
salt_hex => "a9f524b1e819e96d8cc7".
"a04d5471e8b10c84e596",
hash_hex => "8270d9d1a345d3806ab2".
"3b0385702e10f1acc943");
$ppr = Authen::Passphrase::SaltedDigest->new(
algorithm => "SHA-1", salt_random => 20,
passphrase => "passphrase");
$ppr = Authen::Passphrase::SaltedDigest->from_rfc2307(
"{SSHA}gnDZ0aNF04BqsjsDhXAuEPGsy".
"UOp9SSx6BnpbYzHoE1UceixDITllg==");
$algorithm = $ppr->algorithm;
$salt = $ppr->salt;
$salt_hex = $ppr->salt_hex;
$hash = $ppr->hash;
$hash_hex = $ppr->hash_hex;
if($ppr->match($passphrase)) { ...
$userPassword = $ppr->as_rfc2307;
DESCRIPTION
An object of this class encapsulates a passphrase hashed using a generic digest-algorithm-based scheme.
This is a subclass of Authen::Passphrase, and this document assumes that the reader is familiar with the
documentation for that class.
The salt is an arbitrary string of bytes. It is appended to passphrase, and the combined string is
passed through a specified message digest algorithm. The output of the message digest algorithm is the
passphrase hash.
The strength depends entirely on the choice of digest algorithm, so choose according to the level of
security required. SHA-1 is suitable for most applications, but recent work has revealed weaknesses in
the basic structure of MD5, SHA-1, SHA-256, and all similar digest algorithms. A new generation of
digest algorithms emerged in 2008, centred around NIST's competition to design SHA-3. Once these
algorithms have been subjected to sufficient cryptanalysis, the survivors will be preferred over SHA-1
and its generation.
Digest algorithms are generally designed to be as efficient to compute as possible for their level of
cryptographic strength. An unbroken digest algorithm makes brute force the most efficient way to attack
it, but makes no effort to resist a brute force attack. This is a concern in some passphrase-using
applications.
The use of this kind of passphrase scheme is generally recommended for new systems. Choice of digest
algorithm is important: SHA-1 is suitable for most applications. If efficiency of brute force attack is
a concern, see Authen::Passphrase::BlowfishCrypt for an algorithm designed to be expensive to compute.
CONSTRUCTORS
Authen::Passphrase::SaltedDigest->new(ATTR => VALUE, ...)
Generates a new passphrase recogniser object using the generic salted digest algorithm. The
following attributes may be given:
algorithm
Specifies the algorithm to use. If it is a reference to a blessed object, it must be possible to
call the "new" method on that object to generate a digest context object.
If it is a string containing the subsequence "::" then it specifies a module to use. A plain
package name in bareword syntax, optionally preceded by "::" (so that top-level packages can be
recognised as such), is taken as a class name, on which the "new" method will be called to
generate a digest context object. The package name may optionally be followed by "-" to cause
automatic loading of the module, and the "-" (if present) may optionally be followed by a version
number that will be checked against. For example, "Digest::MD5-1.99_53" would load the
Digest::MD5 module and check that it is at least version 1.99_53 (which is the first version that
can be used by this module).
A string not containing "::" and which is understood by Digest->new will be passed to that
function to generate a digest context object.
Any other type of algorithm specifier has undefined behaviour.
The digest context objects must support at least the standard "add" and "digest" methods.
salt
The salt, as a raw string of bytes. Defaults to the empty string, yielding an unsalted scheme.
salt_hex
The salt, as a string of hexadecimal digits. Defaults to the empty string, yielding an unsalted
scheme.
salt_random
Causes salt to be generated randomly. The value given for this attribute must be a non-negative
integer, giving the number of bytes of salt to generate. (The same length as the hash is
recommended.) The source of randomness may be controlled by the facility described in
Data::Entropy.
hash
The hash, as a string of bytes.
hash_hex
The hash, as a string of hexadecimal digits.
passphrase
A passphrase that will be accepted.
The digest algorithm must be given, and either the hash or the passphrase.
Authen::Passphrase::SaltedDigest->from_rfc2307(USERPASSWORD)
Generates a salted-digest passphrase recogniser from the supplied RFC2307 encoding. The scheme
identifier gives the digest algorithm and controls whether salt is permitted. It is followed by a
base 64 string, using standard MIME base 64, which encodes the concatenation of the hash and salt.
The scheme identifiers accepted are "{MD4}" (unsalted MD4), "{MD5}" (unsalted MD5), "{RMD160}"
(unsalted RIPEMD-160), "{SHA}" (unsalted SHA-1), "{SMD5}" (salted MD5), and "{SSHA}" (salted SHA-1).
All scheme identifiers are recognised case-insensitively.
METHODS
$ppr->algorithm
Returns the digest algorithm, in the same form as supplied to the constructor.
$ppr->salt
Returns the salt, in raw form.
$ppr->salt_hex
Returns the salt, as a string of hexadecimal digits.
$ppr->hash
Returns the hash value, in raw form.
$ppr->hash_hex
Returns the hash value, as a string of hexadecimal digits.
$ppr->match(PASSPHRASE)
$ppr->as_rfc2307
These methods are part of the standard Authen::Passphrase interface. Only passphrase recognisers
using certain well-known digest algorithms can be represented in RFC 2307 form.
SEE ALSO
Authen::Passphrase, Crypt::SaltedHash
AUTHOR
Andrew Main (Zefram) <zefram@fysh.org>
COPYRIGHT
Copyright (C) 2006, 2007, 2009, 2010, 2012 Andrew Main (Zefram) <zefram@fysh.org>
LICENSE
This module is free software; you can redistribute it and/or modify it under the same terms as Perl
itself.