package Crypt::PK::DH;
use strict;
use warnings;
use Exporter 'import';
our %EXPORT_TAGS = ( all => [qw( dh_encrypt dh_decrypt dh_sign_message dh_verify_message dh_sign_hash dh_verify_hash dh_shared_secret )] );
our @EXPORT_OK = ( @{ $EXPORT_TAGS{'all'} } );
our @EXPORT = qw();
use CryptX;
use Crypt::PK;
use Crypt::Digest 'digest_data';
use Carp;
use MIME::Base64 qw(encode_base64 decode_base64);
sub new {
my ($class, $f) = @_;
my $self = _new();
$self->import_key($f) if $f;
return $self;
}
sub generate_key {
my $self = shift;
$self->_generate_key(@_);
return $self;
}
sub import_key {
my ($self, $key) = @_;
croak "FATAL: undefined key" unless $key;
my $data;
if (ref($key) eq 'SCALAR') {
$data = $$key;
}
elsif (-f $key) {
$data = Crypt::PK::_slurp_file($key);
}
else {
croak "FATAL: non-existing file '$key'";
}
croak "FATAL: invalid key format" unless $data;
$self->_import($data);
return $self;
}
sub encrypt {
my ($self, $data, $hash_name) = @_;
$hash_name = Crypt::Digest::_trans_digest_name($hash_name||'SHA1');
return $self->_encrypt($data, $hash_name);
}
sub decrypt {
my ($self, $data) = @_;
return $self->_decrypt($data);
}
sub sign_message {
my ($self, $data, $hash_name) = @_;
$hash_name ||= 'SHA1';
my $data_hash = digest_data($hash_name, $data);
return $self->_sign($data_hash);
}
sub verify_message {
my ($self, $sig, $data, $hash_name) = @_;
$hash_name ||= 'SHA1';
my $data_hash = digest_data($hash_name, $data);
return $self->_verify($sig, $data_hash);
}
sub sign_hash {
my ($self, $data_hash) = @_;
return $self->_sign($data_hash);
}
sub verify_hash {
my ($self, $sig, $data_hash) = @_;
return $self->_verify($sig, $data_hash);
}
### FUNCTIONS
sub dh_encrypt {
my $key = shift;
$key = __PACKAGE__->new($key) unless ref $key;
carp "FATAL: invalid 'key' param" unless ref($key) eq __PACKAGE__;
return $key->encrypt(@_);
}
sub dh_decrypt {
my $key = shift;
$key = __PACKAGE__->new($key) unless ref $key;
carp "FATAL: invalid 'key' param" unless ref($key) eq __PACKAGE__;
return $key->decrypt(@_);
}
sub dh_sign_message {
my $key = shift;
$key = __PACKAGE__->new($key) unless ref $key;
carp "FATAL: invalid 'key' param" unless ref($key) eq __PACKAGE__;
return $key->sign_message(@_);
}
sub dh_verify_message {
my $key = shift;
$key = __PACKAGE__->new($key) unless ref $key;
carp "FATAL: invalid 'key' param" unless ref($key) eq __PACKAGE__;
return $key->verify_message(@_);
}
sub dh_sign_hash {
my $key = shift;
$key = __PACKAGE__->new($key) unless ref $key;
carp "FATAL: invalid 'key' param" unless ref($key) eq __PACKAGE__;
return $key->sign_hash(@_);
}
sub dh_verify_hash {
my $key = shift;
$key = __PACKAGE__->new($key) unless ref $key;
carp "FATAL: invalid 'key' param" unless ref($key) eq __PACKAGE__;
return $key->verify_hash(@_);
}
sub dh_shared_secret {
my ($privkey, $pubkey) = @_;
$privkey = __PACKAGE__->new($privkey) unless ref $privkey;
$pubkey = __PACKAGE__->new($pubkey) unless ref $pubkey;
carp "FATAL: invalid 'privkey' param" unless ref($privkey) eq __PACKAGE__ && $privkey->is_private;
carp "FATAL: invalid 'pubkey' param" unless ref($pubkey) eq __PACKAGE__;
return $privkey->shared_secret($pubkey);
}
sub CLONE_SKIP { 1 } # prevent cloning
1;
=pod
=head1 NAME
Crypt::PK::DH - Public key cryptography based on Diffie-Hellman
=head1 SYNOPSIS
### OO interface
#Encryption: Alice
my $pub = Crypt::PK::DH->new('Bob_pub_dh1.key');
my $ct = $pub->encrypt("secret message");
#
#Encryption: Bob (received ciphertext $ct)
my $priv = Crypt::PK::DH->new('Bob_priv_dh1.key');
my $pt = $priv->decrypt($ct);
#Signature: Alice
my $priv = Crypt::PK::DH->new('Alice_priv_dh1.key');
my $sig = $priv->sign_message($message);
#
#Signature: Bob (received $message + $sig)
my $pub = Crypt::PK::DH->new('Alice_pub_dh1.key');
$pub->verify_message($sig, $message) or die "ERROR";
#Shared secret
my $priv = Crypt::PK::DH->new('Alice_priv_dh1.key');
my $pub = Crypt::PK::DH->new('Bob_pub_dh1.key');
my $shared_secret = $priv->shared_secret($pub);
#Key generation
my $pk = Crypt::PK::DH->new();
$pk->generate_key(128);
my $private = $pk->export_key('private');
my $public = $pk->export_key('public');
### Functional interface
#Encryption: Alice
my $ct = dh_encrypt('Bob_pub_dh1.key', "secret message");
#Encryption: Bob (received ciphertext $ct)
my $pt = dh_decrypt('Bob_priv_dh1.key', $ct);
#Signature: Alice
my $sig = dh_sign_message('Alice_priv_dh1.key', $message);
#Signature: Bob (received $message + $sig)
dh_verify_message('Alice_pub_dh1.key', $sig, $message) or die "ERROR";
#Shared secret
my $shared_secret = dh_shared_secret('Alice_priv_dh1.key', 'Bob_pub_dh1.key');
=head1 FUNCTIONS
=head2 dh_encrypt
DH based encryption as implemented by libtomcrypt. See method L</encrypt> below.
my $ct = dh_encrypt($pub_key_filename, $message);
#or
my $ct = dh_encrypt(\$buffer_containing_pub_key, $message);
#or
my $ct = dh_encrypt($pub_key_filename, $message, $hash_name);
#NOTE: $hash_name can be 'SHA1' (DEFAULT), 'SHA256' or any other hash supported by Crypt::Digest
Encryption works similar to the L<Crypt::PK::ECC> encryption whereas shared DH key is computed, and
the hash of the shared key XOR'ed against the plaintext forms the ciphertext.
=head2 dh_decrypt
DH based decryption as implemented by libtomcrypt. See method L</decrypt> below.
my $pt = dh_decrypt($priv_key_filename, $ciphertext);
#or
my $pt = dh_decrypt(\$buffer_containing_priv_key, $ciphertext);
=head2 dh_sign_message
Generate DH signature as implemented by libtomcrypt. See method L</sign_message> below.
my $sig = dh_sign_message($priv_key_filename, $message);
#or
my $sig = dh_sign_message(\$buffer_containing_priv_key, $message);
#or
my $sig = dh_sign_message($priv_key, $message, $hash_name);
=head2 dh_verify_message
Verify DH signature as implemented by libtomcrypt. See method L</verify_message> below.
dh_verify_message($pub_key_filename, $signature, $message) or die "ERROR";
#or
dh_verify_message(\$buffer_containing_pub_key, $signature, $message) or die "ERROR";
#or
dh_verify_message($pub_key, $signature, $message, $hash_name) or die "ERROR";
=head2 dh_sign_hash
Generate DH signature as implemented by libtomcrypt. See method L</sign_hash> below.
my $sig = dh_sign_hash($priv_key_filename, $message_hash);
#or
my $sig = dh_sign_hash(\$buffer_containing_priv_key, $message_hash);
=head2 dh_verify_hash
Verify DH signature as implemented by libtomcrypt. See method L</verify_hash> below.
dh_verify_hash($pub_key_filename, $signature, $message_hash) or die "ERROR";
#or
dh_verify_hash(\$buffer_containing_pub_key, $signature, $message_hash) or die "ERROR";
=head2 dh_shared_secret
DH based shared secret generation. See method L</shared_secret> below.
#on Alice side
my $shared_secret = dh_shared_secret('Alice_priv_dh1.key', 'Bob_pub_dh1.key');
#on Bob side
my $shared_secret = dh_shared_secret('Bob_priv_dh1.key', 'Alice_pub_dh1.key');
=head1 METHODS
=head2 new
my $pk = Crypt::PK::DH->new();
#or
my $pk = Crypt::PK::DH->new($priv_or_pub_key_filename);
#or
my $pk = Crypt::PK::DH->new(\$buffer_containing_priv_or_pub_key);
=head2 generate_key
Uses Yarrow-based cryptographically strong random number generator seeded with
random data taken from C</dev/random> (UNIX) or C<CryptGenRandom> (Win32).
$pk->generate_key($keysize);
### $keysize (in bytes) corresponds to DH params (p, g) predefined by libtomcrypt
# 96 => DH-768
# 128 => DH-1024
# 160 => DH-1280
# 192 => DH-1536
# 224 => DH-1792
# 256 => DH-2048
# 320 => DH-2560
# 384 => DH-3072
# 512 => DH-4096
=head2 import_key
Loads private or public key (exported by L</export_key>).
$pk->import_key($filename);
#or
$pk->import_key(\$buffer_containing_key);
=head2 export_key
my $private = $pk->export_key('private');
#or
my $public = $pk->export_key('public');
=head2 encrypt
my $pk = Crypt::PK::DH->new($pub_key_filename);
my $ct = $pk->encrypt($message);
#or
my $ct = $pk->encrypt($message, $hash_name);
#NOTE: $hash_name can be 'SHA1' (DEFAULT), 'SHA256' or any other hash supported by Crypt::Digest
=head2 decrypt
my $pk = Crypt::PK::DH->new($priv_key_filename);
my $pt = $pk->decrypt($ciphertext);
=head2 sign_message
my $pk = Crypt::PK::DH->new($priv_key_filename);
my $signature = $priv->sign_message($message);
#or
my $signature = $priv->sign_message($message, $hash_name);
#NOTE: $hash_name can be 'SHA1' (DEFAULT), 'SHA256' or any other hash supported by Crypt::Digest
=head2 verify_message
my $pk = Crypt::PK::DH->new($pub_key_filename);
my $valid = $pub->verify_message($signature, $message)
#or
my $valid = $pub->verify_message($signature, $message, $hash_name);
#NOTE: $hash_name can be 'SHA1' (DEFAULT), 'SHA256' or any other hash supported by Crypt::Digest
=head2 sign_hash
my $pk = Crypt::PK::DH->new($priv_key_filename);
my $signature = $priv->sign_hash($message_hash);
=head2 verify_hash
my $pk = Crypt::PK::DH->new($pub_key_filename);
my $valid = $pub->verify_hash($signature, $message_hash);
=head2 shared_secret
# Alice having her priv key $pk and Bob's public key $pkb
my $pk = Crypt::PK::DH->new($priv_key_filename);
my $pkb = Crypt::PK::DH->new($pub_key_filename);
my $shared_secret = $pk->shared_secret($pkb);
# Bob having his priv key $pk and Alice's public key $pka
my $pk = Crypt::PK::DH->new($priv_key_filename);
my $pka = Crypt::PK::DH->new($pub_key_filename);
my $shared_secret = $pk->shared_secret($pka); # same value as computed by Alice
=head2 is_private
my $rv = $pk->is_private;
# 1 .. private key loaded
# 0 .. public key loaded
# undef .. no key loaded
=head2 size
my $size = $pk->size;
# returns key size in bytes or undef if no key loaded
=head2 key2hash
my $hash = $pk->key2hash;
# returns hash like this (or undef if no key loaded):
{
type => 0, # integer: 1 .. private, 0 .. public
size => 256, # integer: key size in bytes
name => "DH-2048", # internal libtomcrypt name
x => "FBC1062F73B9A17BB8473A2F5A074911FA7F20D28FB...", #private key
y => "AB9AAA40774D3CD476B52F82E7EE2D8A8D40CD88BF4...", #public key
}
=head1 SEE ALSO
=over
=item * L<https://en.wikipedia.org/wiki/Diffie%E2%80%93Hellman_key_exchange|https://en.wikipedia.org/wiki/Diffie%E2%80%93Hellman_key_exchange>
=back