man Crypt::OpenSSL::DSA (3): Digital Signature Algorithm using OpenSSL

SYNOPSIS

use Crypt::OpenSSL::DSA;
# generate keys and write out to PEM files
my $dsa = Crypt::OpenSSL::DSA->generate_parameters( 512 );
$dsa->generate_key;
$dsa->write_pub_key( $filename );
$dsa->write_priv_key( $filename );
# using keys from PEM files
my $dsa_priv = Crypt::OpenSSL::DSA->read_priv_key( $filename );
my $sig = $dsa_priv->sign($message);
my $dsa_pub = Crypt::OpenSSL::DSA->read_pub_key( $filename );
my $valid = $dsa_pub->verify($message, $sig);
# using keys from PEM strings
my $dsa_priv = Crypt::OpenSSL::DSA->read_priv_key_str( $key_string );
my $sig = $dsa_priv->sign($message);
my $dsa_pub = Crypt::OpenSSL::DSA->read_pub_key_str( $key_string );
my $valid = $dsa_pub->verify($message, $sig);

DESCRIPTION

Crypt::OpenSSL::DSA implements the DSA (Digital Signature Algorithm) signature verification system.

It is a thin XS wrapper to the DSA functions contained in the OpenSSL crypto library, located at http://www.openssl.org

CLASS METHODS

$dsa = Crypt::OpenSSL::DSA->generate_parameters( $bits, $seed );: Returns a new DSA object and generates the p, q and g parameters necessary to generate keys.
bits is the length of the prime to be generated; the DSS allows a maximum of 1024 bits.
$dsa = Crypt::OpenSSL::DSA->read_params( $filename );: Reads in a parameter PEM file and returns a new DSA object with the p, q and g parameters necessary to generate keys.
$dsa = Crypt::OpenSSL::DSA->read_pub_key( $filename );: Reads in a public key PEM file and returns a new DSA object that can be used to verify DSA signatures.
$dsa = Crypt::OpenSSL::DSA->read_priv_key( $filename );: Reads in a private key PEM file and returns a new DSA object that can be used to sign messages.
$dsa = Crypt::OpenSSL::DSA->read_pub_key_str( $key_string );: Reads in a public key PEM string and returns a new DSA object that can be used to verify DSA signatures. The string should include the -----BEGIN...----- and -----END...----- lines.
$dsa = Crypt::OpenSSL::DSA->read_priv_key_str( $key_string );: Reads in a private key PEM string and returns a new DSA object that can be used to sign messages. The string should include the -----BEGIN...----- and -----END...----- lines.

OBJECT METHODS

$dsa->generate_key;

Generates private and public keys, assuming that $dsa is the return value of generate_parameters.

$sig = $dsa->sign( $message );

Signs $message, returning the signature. Note that $meesage cannot exceed 20 characters in length.

$dsa is the signer's private key.

$sig_obj = $dsa->do_sign( $message );

Similar to "sign", but returns a Crypt::OpenSSL::DSA::Signature object.

$valid = $dsa->verify( $message, $sig );

Verifies that the $sig signature for $message is valid.

$dsa is the signer's public key.

Note: it croaks if the underlying library call returns error (-1).

$valid = $dsa->do_verify( $message, $sig_obj );

Similar to "verify", but uses a Crypt::OpenSSL::DSA::Signature object.

Note: it croaks if the underlying library call returns error (-1).

$dsa->write_params( $filename );

Writes the parameters into a PEM file.

$dsa->write_pub_key( $filename );

Writes the public key into a PEM file.

$dsa->write_priv_key( $filename );

Writes the private key into a PEM file.

$p = $dsa->get_p, $dsa->set_p($p)

Gets/sets the prime number in binary format.

$q = $dsa->get_q, $dsa->set_q($q)

Gets/sets the subprime number (q | p-1) in binary format.

$g = $dsa->get_g, $dsa->set_g($g)

Gets/sets the generator of subgroup in binary format.

$pub_key = $dsa->get_pub_key, $dsa->set_pub_key($pub_key)

Gets/sets the public key (y = g^x) in binary format.

$priv_key = $dsa->get_priv_key, $dsa->set_priv_key($priv_key)

Gets/sets the private key in binary format.

NOTES

Crpyt::DSA is a more mature Perl DSA module, but can be difficult to install, because of the Math::Pari requirement.

Comments, suggestions, and patches welcome.

AUTHOR

T.J. Mather, <[email protected]>

COPYRIGHT

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