NAME

Crypt::OpenPGP::Signature - Signature packet

SYNOPSIS

use Crypt::OpenPGP::Signature;

my $sig = Crypt::OpenPGP::Signature->new(
                           Key  => $secret_key,
                           Data => $plaintext,
                           Type => 0x00,
                 );
my $serialized = $sig->save;

my $sig = Crypt::OpenPGP::Signature->parse($buffer);
my $hashed_data = $sig->hash_data($plaintext);

## Look up public key by $sig->key_id to get $cert, then...

my $is_valid_sig = $cert->key->verify($sig, $hashed_data);

DESCRIPTION

Crypt::OpenPGP::Signature implements PGP signature packets and provides functionality for hashing PGP packets to obtain message digests; these digests are then signed by the secret key to form a signature.

Crypt::OpenPGP::Signature reads and writes both version 3 and version 4 signatures, along with the signature subpackets found in version 4 (see Crypt::OpenPGP::Signature::SubPacket).

USAGE

Crypt::OpenPGP::Signature->new( %arg )

Creates a new signature packet object and returns that object. If there are no arguments in %arg, the object is created empty; this is used, for example, in parse (below), to create an empty packet which is then filled from the data in the buffer.

If you wish to initialize a non-empty object, %arg can contain:

• Data

  A PGP packet object of some kind. Currently the two supported objects are Crypt::OpenPGP::Certificate objects, to create self-signatures for keyrings, and Crypt::OpenPGP::Plaintext objects, for signatures on blocks of data.

  This argument is required (for a non-empty packet).

• Key

  A secret-key certificate that can be used to sign the data. In other words an object of type Crypt::OpenPGP::Certificate that holds a secret key.

  This argument is required.

• Version

  The packet format version of the signature. Valid values are either 3 or 4; version 4 signatures are the default, but will be incompatible with older PGP implementations; for example, PGP2 will only read version 3 signatures; PGP5 can read version 4 signatures, but only on signatures of data packets (not on key signatures).

  This argument is optional; the default is version 4.

• Type

  Specifies the type of signature (data, key, etc.). Valid values can be found in the OpenPGP RFC, section 5.2.1.

  This argument is optional; the default is 0x00, signature of a binary document.

• Digest

  The digest algorithm to use when generating the digest of the data to be signed. See the documentation for Crypt::OpenPGP::Digest for a list of valid values.

  This argument is optional; the default is SHA1.

$sig->save

Serializes the signature packet and returns a string of octets.

Crypt::OpenPGP::Signature->parse($buffer)

Given $buffer, a Crypt::OpenPGP::Buffer object holding (or with offset pointing to) a signature packet, returns a new Crypt::OpenPGP::Signature object, initialized with the signature data in the buffer.

$sig->hash_data(@data)

$sig->key_id

Returns the ID of the key that created the signature.

AUTHOR & COPYRIGHTS

Please see the Crypt::OpenPGP manpage for author, copyright, and license information.