package Crypt::AuthEnc::EAX;
use strict;
use warnings;
use base qw(Crypt::AuthEnc Exporter);
our %EXPORT_TAGS = ( all => [qw( eax_encrypt_authenticate eax_decrypt_verify )] );
our @EXPORT_OK = ( @{ $EXPORT_TAGS{'all'} } );
our @EXPORT = qw();
use CryptX;
use Crypt::Cipher;
### the following methods/functions are implemented in XS:
# - _new
# - DESTROY
# - clone
# - encrypt_add
# - encrypt_done
# - decrypt_add
# - decrypt_done
# - header_add
sub new { my $class = shift; _new(Crypt::Cipher::_trans_cipher_name(shift), @_) }
sub eax_encrypt_authenticate {
my $cipher_name = shift;
my $key = shift;
my $nonce = shift;
my $header = shift;
my $plaintext = shift;
my $m = Crypt::AuthEnc::EAX->new($cipher_name, $key, $nonce);
$m->header_add($header) if defined $header;
my $ct = $m->encrypt_add($plaintext);
my $tag = $m->encrypt_done;
return ($ct, $tag);
}
sub eax_decrypt_verify {
my $cipher_name = shift;
my $key = shift;
my $nonce = shift;
my $header = shift;
my $ciphertext = shift;
my $tag = shift;
my $m = Crypt::AuthEnc::EAX->new($cipher_name, $key, $nonce);
$m->header_add($header) if defined $header;
my $ct = $m->decrypt_add($ciphertext);
return $m->decrypt_done($tag) ? $ct : undef;
}
1;
=pod
=head1 NAME
Crypt::AuthEnc::EAX - Authenticated encryption in EAX mode
=head1 SYNOPSIS
### example 1
use Crypt::AuthEnc::EAX;
# encrypt + authenticate
my $ae = Crypt::AuthEnc::EAX->new("AES", $key, $nonce);
$ae->header_add('headerdata part1');
$ae->header_add('headerdata part2');
$ct = $ae->encrypt_add('data1');
$ct = $ae->encrypt_add('data2');
$ct = $ae->encrypt_add('data3');
$tag = $ae->encrypt_done();
# decrypt + verify
my $ae = Crypt::AuthEnc::EAX->new("AES", $key, $nonce);
$ae->header_add('headerdata part1');
$ae->header_add('headerdata part2');
$pt = $ae->decrypt_add('ciphertext1');
$pt = $ae->decrypt_add('ciphertext2');
$pt = $ae->decrypt_add('ciphertext3');
my $result = $ae->decrypt_done($tag);
#or
my $tag_dec = $ae->decrypt_done;
die "TAG mismatch" unless $tag eq $tag_dec;
### example 2
use Crypt::AuthEnc::EAX qw(eax_encrypt_authenticate eax_decrypt_verify);
my ($ciphertext, $tag) = eax_encrypt_authenticate('AES', $key, $nonce, $header, $plaintext);
my $plaintext = eax_decrypt_verify('AES', $key, $nonce, $header, $ciphertext, $tag);
=head1 DESCRIPTION
EAX is a mode that requires a cipher, CTR and OMAC support and provides encryption and authentication.
It is initialized with a random nonce that can be shared publicly, a header which can be fixed and public,
and a random secret symmetric key.
=head1 EXPORT
Nothing is exported by default.
You can export selected functions:
use Crypt::AuthEnc::EAX qw(eax_encrypt_authenticate eax_decrypt_verify);
=head1 FUNCTIONS
=head2 eax_encrypt_authenticate
my ($ciphertext, $tag) = eax_encrypt_authenticate($cipher, $key, $nonce, $header, $plaintext);
# $cipher .. 'AES' or name of any other cipher with 16-byte block len
# $key ..... AES key of proper length (128/192/256bits)
# $nonce ... unique nonce/salt (no need to keep it secret)
# $header .. meta-data you want to send with the message but not have encrypted
=head2 eax_decrypt_verify
my $plaintext = eax_decrypt_verify($cipher, $key, $nonce, $header, $ciphertext, $tag);
# on error returns undef
=head1 METHODS
=head2 new
my $ae = Crypt::AuthEnc::EAX->new($cipher, $key, $nonce);
#or
my $ae = Crypt::AuthEnc::EAX->new($cipher, $key, $nonce, $header);
# $cipher .. 'AES' or name of any other cipher with 16-byte block len
# $key ..... AES key of proper length (128/192/256bits)
# $nonce ... unique nonce/salt (no need to keep it secret)
# $header .. meta-data you want to send with the message but not have encrypted
=head2 header_add
$ae->header_add($header_data); #can be called multiple times
=head2 encrypt_add
$ciphertext = $ae->encrypt_add($data); #can be called multiple times
=head2 encrypt_done
$tag = $ae->encrypt_done();
=head2 decrypt_add
$plaintext = $ae->decrypt_add($ciphertext); #can be called multiple times
=head2 decrypt_done
my $result = $ae->decrypt_done($tag); # returns 1 (success) or 0 (failure)
#or
my $tag = $ae->decrypt_done; # returns $tag value
=head2 clone
my $ae_new = $ae->clone;
=head1 SEE ALSO
=over
=item * L<CryptX|CryptX>, L<Crypt::Mode::CCM|Crypt::Mode::CCM>, L<Crypt::Mode::GCM|Crypt::Mode::GCM>, L<Crypt::Mode::OCB|Crypt::Mode::OCB>
=item * L<https://en.wikipedia.org/wiki/EAX_mode|https://en.wikipedia.org/wiki/EAX_mode>
=back