File Coverage

blib/lib/Crypt/ECDH_ES.pm

Criterion	Covered	Total	%
statement	50	54	92.5
branch	3	6	50.0
condition			n/a
subroutine	10	11	90.9
pod	3	3	100.0
total	66	74	89.1

package Crypt::ECDH_ES;
$Crypt::ECDH_ES::VERSION = '0.004';
use strict;
use warnings;

use Carp;
use Crypt::Curve25519;
use Crypt::URandom qw/urandom/;
use Crypt::Rijndael;
use Digest::SHA qw/sha256 hmac_sha256/;

use Exporter 5.57 'import';
our @EXPORT_OK = qw/ecdhes_encrypt ecdhes_decrypt ecdhes_generate_key/;
our %EXPORT_TAGS = (all => \@EXPORT_OK);

my $format = 'C/a C/a n/a N/a';

sub ecdhes_encrypt {
	my ($public_key, $data) = @_;

	my $private = curve25519_secret_key(urandom(32));
	my $public  = curve25519_public_key($private);
	my $shared  = curve25519_shared_secret($private, $public_key);

	my ($encrypt_key, $sign_key) = unpack 'a16 a16', sha256($shared);
	my $iv     = substr sha256($public), 0, 16;
	my $cipher = Crypt::Rijndael->new($encrypt_key, Crypt::Rijndael::MODE_CBC);
	$cipher->set_iv($iv);

	my $pad_length = 16 - length($data) % 16;
	my $padding = chr($pad_length) x $pad_length;

	my $ciphertext = $cipher->encrypt($data . $padding);
	my $mac = hmac_sha256($iv . $ciphertext, $sign_key);
	return pack $format, '', $public, $mac, $ciphertext;
}

sub ecdhes_decrypt {
	my ($private_key, $packed_data) = @_;

	my ($options, $public, $mac, $ciphertext) = unpack $format, $packed_data;
	croak 'Unknown options' if $options ne '';

	my $shared = curve25519_shared_secret($private_key, $public);
	my ($encrypt_key, $sign_key) = unpack 'a16 a16', sha256($shared);
	my $iv     = substr sha256($public), 0, 16;
	croak 'MAC is incorrect' if hmac_sha256($iv . $ciphertext, $sign_key) ne $mac;
	my $cipher = Crypt::Rijndael->new($encrypt_key, Crypt::Rijndael::MODE_CBC);
	$cipher->set_iv($iv);

	my $plaintext = $cipher->decrypt($ciphertext);
	my $pad_length = ord substr $plaintext, -1;
	substr($plaintext, -$pad_length, $pad_length, '') eq chr($pad_length) x $pad_length or croak 'Incorrectly padded';
	return $plaintext;
}

sub ecdhes_generate_key {
	my $buf = urandom(32);
	my $secret = curve25519_secret_key($buf);
	my $public = curve25519_public_key($secret);
	return ($public, $secret);
}

1;

#ABSTRACT: A fast and small hybrid crypto system

__END__