NAME

Crypt::PK::DH - Public key cryptography based on Diffie-Hellman

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');

METHODS

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);

generate_key

Uses Yarrow-based cryptographically strong random number generator seeded with random data taken from /dev/random (UNIX) or 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

import_key

Loads private or public key (exported by "export_key").

$pk->import_key($filename);
#or
$pk->import_key(\$buffer_containing_key);

export_key

my $private = $pk->export_key('private');
#or
my $public = $pk->export_key('public');

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

decrypt

my $pk = Crypt::PK::DH->new($priv_key_filename);
my $pt = $pk->decrypt($ciphertext);

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

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

sign_hash

my $pk = Crypt::PK::DH->new($priv_key_filename);
my $signature = $priv->sign_hash($message_hash);

verify_hash

my $pk = Crypt::PK::DH->new($pub_key_filename);
my $valid = $pub->verify_hash($signature, $message_hash);

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

is_private

my $rv = $pk->is_private;
# 1 .. private key loaded
# 0 .. public key loaded
# undef .. no key loaded

size

my $size = $pk->size;
# returns key size in bytes or undef if no key loaded

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
}

FUNCTIONS

dh_encrypt

DH based encryption as implemented by libtomcrypt. See method "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 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.

dh_decrypt

DH based decryption as implemented by libtomcrypt. See method "decrypt" below.

my $pt = dh_decrypt($priv_key_filename, $ciphertext);
#or
my $pt = dh_decrypt(\$buffer_containing_priv_key, $ciphertext);

dh_sign_message

Generate DH signature as implemented by libtomcrypt. See method "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);

dh_verify_message

Verify DH signature as implemented by libtomcrypt. See method "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";

dh_sign_hash

Generate DH signature as implemented by libtomcrypt. See method "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);

dh_verify_hash

Verify DH signature as implemented by libtomcrypt. See method "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";

dh_shared_secret

DH based shared secret generation. See method "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');

SEE ALSO

• https://en.wikipedia.org/wiki/Diffie%E2%80%93Hellman_key_exchange

cpanm CryptX

perl -MCPAN -e shell
install CryptX