NAME Crypt::Curve25519 - Generate shared secret using elliptic-curve Diffie-Hellman function VERSION version 0.05 SYNOPSIS use Crypt::Curve25519; # Alice: my $alice_secret_key = curve25519_secret_key(random_32_bytes()); my $alice_public_key = curve25519_public_key( $alice_secret_key ); # Bob: my $bob_secret_key = curve25519_secret_key(random_32_bytes()); my $bob_public_key = curve25519_public_key( $bob_secret_key ); # Alice and Bob exchange their public keys my $alice_public_key_hex = unpack('H64', $alice_public_key); my $bob_public_key_hex = unpack('H64', $bob_public_key); # Alice calculates shared secret to communicate with Bob my $shared_secret_with_bob = curve25519_shared_secret( $alice_secret_key, pack('H64', $bob_public_key_hex) ); # Bob calculates shared secret to communicate with Alice my $shared_secret_with_alice = curve25519_shared_secret( $bob_secret_key, pack('H64', $alice_public_key_hex) ); # Shared secrets are equal die "Something horrible has happend!" unless $shared_secret_with_bob eq $shared_secret_with_alice; This package provides also simplified OO interface: use Crypt::Curve25519 (); my $c = Crypt::Curve25519->new(); # Alice: my $alice_secret_key_hex = $c->secret_key(random_hexencoded_32_bytes()); my $alice_public_key_hex = $c->public_key( $alice_secret_key_hex ); # Bob: my $bob_secret_key_hex = $c->secret_key(random_hexencoded_32_bytes()); my $bob_public_key_hex = $c->public_key( $bob_secret_key_hex ); # Alice and Bob exchange their public keys # Alice calculates shared secret to communicate with Bob my $shared_secret_with_bob_hex = $c->shared_secret( $alice_secret_key_hex, $bob_public_key_hex); # Bob calculates shared secret to communicate with Alice my $shared_secret_with_alice_hex = $c->shared_secret( $bob_secret_key_hex, $alice_public_key_hex); # Shared secrets are equal die "Something horrible has happend!" unless $shared_secret_with_bob_hex eq $shared_secret_with_alice_hex; Example functions to generate pseudo-random private secret key: sub random_32_bytes { return join('', map { chr(int(rand(255))) } 1 .. 32); } sub random_hexencoded_32_bytes { return unpack('H64', random_32_bytes()); } DESCRIPTION Curve25519 is a state-of-the-art Diffie-Hellman function suitable for a wide variety of applications. Given a user's 32-byte secret key, Curve25519 computes the user's 32-byte public key. Given the user's 32-byte secret key and another user's 32-byte public key, Curve25519 computes a 32-byte secret shared by the two users. This secret can then be used to authenticate and encrypt messages between the two users. METHODS new my $c = Crypt::Curve25519->new(); Create a new object secret_key my $my_secret_key_hex = $c->secret_key( $my_random_32byte_string_hex ); Using hex encoded 32-byte random string from cryptographically safe source create masked secret key. public_key my $public_key_hex = $c->public_key( $my_secret_key_hex ); Using hex encoded masked secret key generate corresponding hex encoded 32-byte Curve25519 public key. shared_secret my $shared_secret_hex = $c->shared_secret( $my_secret_key_hex, $his_public_key_hex ); Using provided hex encoded keys generate 32-byte hex encoded shared secret, that both parties can use without disclosing their private secret keys. generate Access to primitive method is also provided. my $key_hex = $c->generate($my_secret_key_hex, $basepoint_hex); # public key if ( $basepoint_hex eq unpack("H64", pack("H64", "09")) ) { print "\$key_hex is a public key\n"; } elsif ( $basepoint_hex eq $his_public_key_hex ) { print "\$key_hex is a shared secret\n"; } Using provided hex encoded secret key and depending on the 32-byte hex encoded basepoint generate 32-byte hex encoded public key or shared secret. FUNCTIONS curve25519_secret_key my $my_secret_key = curve25519_secret_key($my_random_32byte_string); Using provided 32-byte random string from cryptographically safe source create masked secret key. curve25519_public_key my $public_key = curve25519_public_key($my_secret_key); Using masked secret key generate corresponding 32-byte Curve25519 public key. curve25519_shared_secret my $shared_secret = curve25519_shared_secret( $my_secret_key, $his_public_key ); Using provided keys generate 32-byte shared secret, that both parties can use without disclosing their private secret keys. curve25519 Access to primitive function is also provided. use Crypt::Curve25519 'curve25519'; my $key = curve25519($my_secret_key, $basepoint); # public key if ( $basepoint eq pack('H64', '09') ) { print "\$key is a public key\n"; } elsif ( $basepoint eq $his_public_key ) { print "\$key is a shared secret\n"; } Using provided secret key and depending on the 32-byte basepoint generate 32-byte public key or shared secret. SEE ALSO * AUTHOR Alex J. G. Burzyński COPYRIGHT AND LICENSE This software is copyright (c) 2014 by Alex J. G. Burzyński . This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.