Crypt::PK::X25519(3)

NAME
Crypt::PK::X25519 - Asymmetric cryptography based on X25519

SYNOPSIS
 use Crypt::PK::X25519;

 my $alice = Crypt::PK::X25519->new->generate_key;
 my $bob = Crypt::PK::X25519->new->generate_key;
 my $alice_secret = $alice->shared_secret($bob);
 my $bob_secret = $bob->shared_secret($alice);
 die "ERROR" unless $alice_secret eq $bob_secret;

 #Load key
 my $pk = Crypt::PK::X25519->new;
 my $pk_hex = "EA7806F721A8570512C8F6EFB4E8D620C49A529E4DF5EAA77DEC646FB1E87E41";
 $pk->import_key_raw(pack("H*", $pk_hex), "public");
 my $sk = Crypt::PK::X25519->new;
 my $sk_hex = "002F93D10BA5728D8DD8E9527721DABA3261C0BB1BEFDE7B4BBDAC631D454651";
 $sk->import_key_raw(pack("H*", $sk_hex), "private");

 #Key generation
 my $pk = Crypt::PK::X25519->new->generate_key;
 my $private_der = $pk->export_key_der('private');
 my $public_der  = $pk->export_key_der('public');
 my $private_pem = $pk->export_key_pem('private');
 my $public_pem  = $pk->export_key_pem('public');
 my $private_raw = $pk->export_key_raw('private');
 my $public_raw  = $pk->export_key_raw('public');
 my $private_jwk = $pk->export_key_jwk('private');
 my $public_jwk  = $pk->export_key_jwk('public');

DESCRIPTION
Since: CryptX-0.067

METHODS

  new
 my $source = Crypt::PK::X25519->new();
 $source->generate_key;

 my $public_der = $source->export_key_der('public');
 my $pub = Crypt::PK::X25519->new(\$public_der);

 my $private_pem = $source->export_key_pem('private', 'secret', 'AES-256-CBC');
 my $priv = Crypt::PK::X25519->new(\$private_pem, 'secret');

Passing $filename or "\$buffer" to "new" is equivalent: both forms immediately import the key material into the new object.

  generate_key
Uses the bundled "chacha20" PRNG via "rng_make_prng()". The exact OS entropy source is handled by the underlying LibTomCrypt RNG setup. Returns the object itself (for chaining).

 $pk->generate_key;

  import_key
Loads private or public key in DER or PEM format.

 my $source = Crypt::PK::X25519->new();
 $source->generate_key;

 my $public_der = $source->export_key_der('public');
 my $pub = Crypt::PK::X25519->new();
 $pub->import_key(\$public_der);

 my $private_pem = $source->export_key_pem('private', 'secret', 'AES-256-CBC');
 my $priv = Crypt::PK::X25519->new();
 $priv->import_key(\$private_pem, 'secret');

The same method also accepts filenames instead of buffers.

Loading private or public keys from a Perl HASH:

 $pk->import_key($hashref);

 # the $hashref is either a key exported via key2hash
 $pk->import_key({
      curve => "x25519",
      pub   => "EA7806F721A8570512C8F6EFB4E8D620C49A529E4DF5EAA77DEC646FB1E87E41",
      priv  => "002F93D10BA5728D8DD8E9527721DABA3261C0BB1BEFDE7B4BBDAC631D454651",
 });

 # or a hash with items corresponding to JWK (JSON Web Key)
 $pk->import_key({
       kty => "OKP",
       crv => "X25519",
       d   => "AC-T0Qulco2N2OlSdyHaujJhwLsb7957S72sYx1FRlE",
       x   => "6ngG9yGoVwUSyPbvtOjWIMSaUp5N9eqnfexkb7HofkE",
 });

Supported key formats:

 # all formats can be loaded from a file
 my $pk = Crypt::PK::X25519->new($filename);

 # or from a buffer containing the key
 my $pk = Crypt::PK::X25519->new(\$buffer_with_key);

•   X25519 private keys in PEM format

     -----BEGIN X25519 PRIVATE KEY-----
     MC4CAQAwBQYDK2VuBCIEIAAvk9ELpXKNjdjpUnch2royYcC7G+/ee0u9rGMdRUZR
     -----END X25519 PRIVATE KEY-----

•   X25519 private keys in password protected PEM format

     -----BEGIN X25519 PRIVATE KEY-----
     Proc-Type: 4,ENCRYPTED
     DEK-Info: DES-CBC,DEEFD3D6B714E75A

     dfFWP5bKn49aZ993NVAhQQPdFWgsTb4j8CWhRjGBVTPl6ITstAL17deBIRBwZb7h
     pAyIka81Kfs=
     -----END X25519 PRIVATE KEY-----

•   X25519 public keys in PEM format

     -----BEGIN PUBLIC KEY-----
     MCowBQYDK2VuAyEA6ngG9yGoVwUSyPbvtOjWIMSaUp5N9eqnfexkb7HofkE=
     -----END PUBLIC KEY-----

•   PKCS#8 private keys

     -----BEGIN PRIVATE KEY-----
     MC4CAQAwBQYDK2VuBCIEIAAvk9ELpXKNjdjpUnch2royYcC7G+/ee0u9rGMdRUZR
     -----END PRIVATE KEY-----

•   PKCS#8 encrypted private keys

     -----BEGIN ENCRYPTED PRIVATE KEY-----
     MIGHMEsGCSqGSIb3DQEFDTA+MCkGCSqGSIb3DQEFDDAcBAiS0NOFZmjJswICCAAw
     DAYIKoZIhvcNAgkFADARBgUrDgMCBwQIGd40Hdso8Y4EONSRCTrqvftl9hl3zbH9
     2QmHF1KJ4HDMdLDRxD7EynonCw2SV7BO+XNRHzw2yONqiTybfte7nk9t
     -----END ENCRYPTED PRIVATE KEY-----

•   X25519 private keys in JSON Web Key (JWK) format

    See <https://www.rfc-editor.org/rfc/rfc8037>

     {
      "kty":"OKP",
      "crv":"X25519",
      "x":"6ngG9yGoVwUSyPbvtOjWIMSaUp5N9eqnfexkb7HofkE",
      "d":"AC-T0Qulco2N2OlSdyHaujJhwLsb7957S72sYx1FRlE",
     }

    BEWARE: For JWK support you need to have JSON module installed.

•   X25519 public keys in JSON Web Key (JWK) format

     {
      "kty":"OKP",
      "crv":"X25519",
      "x":"6ngG9yGoVwUSyPbvtOjWIMSaUp5N9eqnfexkb7HofkE",
     }

    BEWARE: For JWK support you need to have JSON module installed.

  import_key_raw
Import raw public/private key - can load raw key data exported by "export_key_raw".

 $pk->import_key_raw($key, 'public');
 $pk->import_key_raw($key, 'private');

  export_key_der
Returns the key as a binary DER-encoded string.

 my $private_der = $pk->export_key_der('private');
 #or
 my $public_der = $pk->export_key_der('public');

  export_key_pem
Returns the key as a PEM-encoded string (ASCII).

 my $private_pem = $pk->export_key_pem('private');
 #or
 my $public_pem = $pk->export_key_pem('public');

Support for password protected PEM keys

 my $private_pem = $pk->export_key_pem('private', $password);
 #or
 my $private_pem = $pk->export_key_pem('private', $password, $cipher);

 # supported ciphers: 'DES-CBC'
 #                    'DES-EDE3-CBC'
 #                    'SEED-CBC'
 #                    'CAMELLIA-128-CBC'
 #                    'CAMELLIA-192-CBC'
 #                    'CAMELLIA-256-CBC'
 #                    'AES-128-CBC'
 #                    'AES-192-CBC'
 #                    'AES-256-CBC' (DEFAULT)

  export_key_jwk
Returns a JSON string, or a hashref if the optional second argument is true.

Exports public/private keys as a JSON Web Key (JWK).

 my $private_json_text = $pk->export_key_jwk('private');
 #or
 my $public_json_text = $pk->export_key_jwk('public');

Also exports public/private keys as a Perl HASH with JWK structure.

 my $jwk_hash = $pk->export_key_jwk('private', 1);
 #or
 my $jwk_hash = $pk->export_key_jwk('public', 1);

BEWARE: For JWK support you need to have JSON module installed.

  export_key_raw
Returns the raw key as a binary string.

Export raw public/private key

 my $private_bytes = $pk->export_key_raw('private');
 #or
 my $public_bytes = $pk->export_key_raw('public');

  shared_secret
Returns the shared secret as a binary string (raw bytes).

  # Alice having her priv key $pk and Bob's public key $pkb
  my $pk  = Crypt::PK::X25519->new($priv_key_filename);
  my $pkb = Crypt::PK::X25519->new($pub_key_filename);
  my $shared_secret = $pk->shared_secret($pkb);

  # Bob having his priv key $pk and Alice's public key $pka
  my $pk = Crypt::PK::X25519->new($priv_key_filename);
  my $pka = Crypt::PK::X25519->new($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

  key2hash
Returns a hashref with the key components, or "undef" if no key is loaded.

 my $hash = $pk->key2hash;

 # returns hash like this (or undef if no key loaded):
 {
   curve => "x25519",
   # raw public key as a hexadecimal string
   pub   => "EA7806F721A8570512C8F6EFB4E8D620C49A529E4DF5EAA77DEC646FB1E87E41",
   # raw private key as a hexadecimal string. undef if key is public only
   priv  => "002F93D10BA5728D8DD8E9527721DABA3261C0BB1BEFDE7B4BBDAC631D454651",
 }

OpenSSL interoperability
 # Generate a key with OpenSSL
 # openssl genpkey -algorithm x25519 -out x25519_priv.pem
 # openssl pkey -in x25519_priv.pem -pubout -out x25519_pub.pem

 # Load the OpenSSL-generated key in CryptX
 use Crypt::PK::X25519;
 my $alice = Crypt::PK::X25519->new("x25519_priv.pem");
 my $bob_pub = Crypt::PK::X25519->new("bob_x25519_pub.pem");

 # Derive shared secret
 my $shared_secret = $alice->shared_secret($bob_pub);

 # Export CryptX key for OpenSSL
 my $pem = $alice->export_key_pem('private');
 # then: openssl pkey -in priv.pem -text -noout

SEE ALSO

•   <https://en.wikipedia.org/wiki/Curve25519>

•   <https://www.rfc-editor.org/rfc/rfc7748>