|binary||This is the most compact form, but it is not well suited for printing or embedding in places that cant handle arbitrary data.|
|hex||A twice as long string of lowercase hexadecimal digits.|
|base64||A string of portable printable characters. This is the base64 encoded representation of the digest with any trailing padding removed. The string will be about 30% longer than the binary version. MIME::Base64 tells you more about this encoding.|
use Digest::MD5 qw(md5);
$digest = md5($message);
There are also versions of the functions with _hex or _base64 appended to the name, which returns the digest in the indicated form.
The following methods are available for all Digest:: modules:
$ctx = Digest->XXX($arg,...) $ctx = Digest->new(XXX => $arg,...) $ctx = Digest::XXX->new($arg,...) The constructor returns some object that encapsulate the state of the message-digest algorithm. You can add data to the object and finally ask for the digest. The XXX should of course be replaced by the proper name of the digest algorithm you want to use.
The two first forms are simply syntactic sugar which automatically load the right module on first use. The second form allow you to use algorithm names which contains letters which are not legal perl identifiers, e.g. SHA-1. If no implementation for the given algorithm can be found, then an exception is raised.
If new() is called as an instance method (i.e. $ctx->new) it will just reset the state the object to the state of a newly created object. No new object is created in this case, and the return value is the reference to the object (i.e. $ctx).
$other_ctx = $ctx->clone The clone method creates a copy of the digest state object and returns a reference to the copy. $ctx->reset This is just an alias for $ctx->new. $ctx->add( $data ) $ctx->add( $chunk1, $chunk2, ... ) The string value of the $data provided as argument is appended to the message we calculate the digest for. The return value is the $ctx object itself.
If more arguments are provided then they are all appended to the message, thus all these lines will have the same effect on the state of the $ctx object:
$ctx->add("a"); $ctx->add("b"); $ctx->add("c"); $ctx->add("a")->add("b")->add("c"); $ctx->add("a", "b", "c"); $ctx->add("abc");
$ctx->addfile( $io_handle ) The $io_handle is read until EOF and the content is appended to the message we calculate the digest for. The return value is the $ctx object itself.
The addfile() method will croak() if it fails reading data for some reason. If it croaks it is unpredictable what the state of the $ctx object will be in. The addfile() method might have been able to read the file partially before it failed. It is probably wise to discard or reset the $ctx object if this occurs.
In most cases you want to make sure that the $io_handle is in binmode before you pass it as argument to the addfile() method.
$ctx->add_bits( $data, $nbits ) $ctx->add_bits( $bitstring ) The add_bits() method is an alternative to add() that allow partial bytes to be appended to the message. Most users should just ignore this method as partial bytes is very unlikely to be of any practical use.
The two argument form of add_bits() will add the first $nbits bits from $data. For the last potentially partial byte only the high order $nbits % 8 bits are used. If $nbits is greater than length($data) * 8, then this method would do the same as $ctx->add($data).
The one argument form of add_bits() takes a $bitstring of 1 and 0 chars as argument. Its a shorthand for $ctx->add_bits(pack("B*", $bitstring), length($bitstring)).
The return value is the $ctx object itself.
This example shows two calls that should have the same effect:
$ctx->add_bits("111100001010"); $ctx->add_bits("\xF0\xA0", 12);
Most digest algorithms are byte based and for these it is not possible to add bits that are not a multiple of 8, and the add_bits() method will croak if you try.
$ctx->digest Return the binary digest for the message.
Note that the digest operation is effectively a destructive, read-once operation. Once it has been performed, the $ctx object is automatically reset and can be used to calculate another digest value. Call $ctx->clone->digest if you want to calculate the digest without resetting the digest state.
$ctx->hexdigest Same as $ctx->digest, but will return the digest in hexadecimal form. $ctx->b64digest Same as $ctx->digest, but will return the digest as a base64 encoded string.
This table should give some indication on the relative speed of different algorithms. It is sorted by throughput based on a benchmark done with of some implementations of this API:
Algorithm Size Implementation MB/s MD4 128 Digest::MD4 v1.3 165.0 MD5 128 Digest::MD5 v2.33 98.8 SHA-256 256 Digest::SHA2 v1.1.0 66.7 SHA-1 160 Digest::SHA v4.3.1 58.9 SHA-1 160 Digest::SHA1 v2.10 48.8 SHA-256 256 Digest::SHA v4.3.1 41.3 Haval-256 256 Digest::Haval256 v1.0.4 39.8 SHA-384 384 Digest::SHA2 v1.1.0 19.6 SHA-512 512 Digest::SHA2 v1.1.0 19.3 SHA-384 384 Digest::SHA v4.3.1 19.2 SHA-512 512 Digest::SHA v4.3.1 19.2 Whirlpool 512 Digest::Whirlpool v1.0.2 13.0 MD2 128 Digest::MD2 v2.03 9.5 Adler-32 32 Digest::Adler32 v0.03 1.3 CRC-16 16 Digest::CRC v0.05 1.1 CRC-32 32 Digest::CRC v0.05 1.1 MD5 128 Digest::Perl::MD5 v1.5 1.0 CRC-CCITT 16 Digest::CRC v0.05 0.8
These numbers was achieved Apr 2004 with ActivePerl-5.8.3 running under Linux on a P4 2.8 GHz CPU. The last 5 entries differ by being pure perl implementations of the algorithms, which explains why they are so slow.
Digest::Adler32, Digest::CRC, Digest::Haval256, Digest::HMAC, Digest::MD2, Digest::MD4, Digest::MD5, Digest::SHA, Digest::SHA1, Digest::SHA2, Digest::Whirlpool
New digest implementations should consider subclassing from Digest::base.
Gisle Aas <firstname.lastname@example.org>
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
Copyright 1998-2006 Gisle Aas. Copyright 1995,1996 Neil Winton.
|perl v5.20.3||DIGEST (3)||2011-10-02|