1Crypt::Curve25519(3) User Contributed Perl Documentation Crypt::Curve25519(3)
2
6 Crypt::Curve25519 - Generate shared secret using elliptic-curve
7 Diffie-Hellman function
8
10 version 0.06
11
13 use Crypt::Curve25519;
14 # Alice:
16 my $alice_secret_key = curve25519_secret_key(random_32_bytes());
17 my $alice_public_key = curve25519_public_key( $alice_secret_key );
18 # Bob:
20 my $bob_secret_key = curve25519_secret_key(random_32_bytes());
21 my $bob_public_key = curve25519_public_key( $bob_secret_key );
22 # Alice and Bob exchange their public keys
24 my $alice_public_key_hex = unpack('H64', $alice_public_key);
25 my $bob_public_key_hex = unpack('H64', $bob_public_key);
26 # Alice calculates shared secret to communicate with Bob
28 my $shared_secret_with_bob = curve25519_shared_secret(
29 $alice_secret_key,
30 pack('H64', $bob_public_key_hex)
31 );
32 # Bob calculates shared secret to communicate with Alice
34 my $shared_secret_with_alice = curve25519_shared_secret(
35 $bob_secret_key,
36 pack('H64', $alice_public_key_hex)
37 );
38 # Shared secrets are equal
40 die "Something horrible has happend!"
41 unless $shared_secret_with_bob eq $shared_secret_with_alice;
42 This package provides also simplified OO interface:
44 use Crypt::Curve25519 ();
46 my $c = Crypt::Curve25519->new();
48 # Alice:
50 my $alice_secret_key_hex = $c->secret_key(random_hexencoded_32_bytes());
51 my $alice_public_key_hex = $c->public_key( $alice_secret_key_hex );
52 # Bob:
54 my $bob_secret_key_hex = $c->secret_key(random_hexencoded_32_bytes());
55 my $bob_public_key_hex = $c->public_key( $bob_secret_key_hex );
56 # Alice and Bob exchange their public keys
58 # Alice calculates shared secret to communicate with Bob
60 my $shared_secret_with_bob_hex = $c->shared_secret(
61 $alice_secret_key_hex,
62 $bob_public_key_hex);
63 # Bob calculates shared secret to communicate with Alice
65 my $shared_secret_with_alice_hex = $c->shared_secret(
66 $bob_secret_key_hex,
67 $alice_public_key_hex);
68 # Shared secrets are equal
70 die "Something horrible has happend!"
71 unless $shared_secret_with_bob_hex eq $shared_secret_with_alice_hex;
72 Example functions to generate pseudo-random private secret key:
74 sub random_32_bytes {
76 return join('', map { chr(int(rand(255))) } 1 .. 32);
77 }
78 sub random_hexencoded_32_bytes {
80 return unpack('H64', random_32_bytes());
81 }
82
84 Curve25519 is a state-of-the-art Diffie-Hellman function suitable for a
85 wide variety of applications.
86 Given a user's 32-byte secret key, Curve25519 computes the user's
88 32-byte public key. Given the user's 32-byte secret key and another
89 user's 32-byte public key, Curve25519 computes a 32-byte secret shared
90 by the two users. This secret can then be used to authenticate and
91 encrypt messages between the two users.
92
94 new
95 my $c = Crypt::Curve25519->new();
96 Create a new object
98 secret_key
100 my $my_secret_key_hex = $c->secret_key( $my_random_32byte_string_hex );
101 Using hex encoded 32-byte random string from cryptographically safe
103 source create masked secret key.
104 public_key
106 my $public_key_hex = $c->public_key( $my_secret_key_hex );
107 Using hex encoded masked secret key generate corresponding hex encoded
109 32-byte Curve25519 public key.
110 shared_secret
112 my $shared_secret_hex = $c->shared_secret(
113 $my_secret_key_hex, $his_public_key_hex
114 );
115 Using provided hex encoded keys generate 32-byte hex encoded shared
117 secret, that both parties can use without disclosing their private
118 secret keys.
119 generate
121 Access to primitive method is also provided.
122 my $key_hex = $c->generate($my_secret_key_hex, $basepoint_hex);
124 # public key
126 if ( $basepoint_hex eq unpack("H64", pack("H64", "09")) ) {
127 print "\$key_hex is a public key\n";
128 }
129 elsif ( $basepoint_hex eq $his_public_key_hex ) {
130 print "\$key_hex is a shared secret\n";
131 }
132 Using provided hex encoded secret key and depending on the 32-byte hex
134 encoded basepoint generate 32-byte hex encoded public key or shared
135 secret.
136
138 curve25519_secret_key
139 my $my_secret_key = curve25519_secret_key($my_random_32byte_string);
140 Using provided 32-byte random string from cryptographically safe source
142 create masked secret key.
143 curve25519_public_key
145 my $public_key = curve25519_public_key($my_secret_key);
146 Using masked secret key generate corresponding 32-byte Curve25519
148 public key.
149 curve25519_shared_secret
151 my $shared_secret = curve25519_shared_secret(
152 $my_secret_key, $his_public_key
153 );
154 Using provided keys generate 32-byte shared secret, that both parties
156 can use without disclosing their private secret keys.
157 curve25519
159 Access to primitive function is also provided.
160 use Crypt::Curve25519 'curve25519';
162 my $key = curve25519($my_secret_key, $basepoint);
164 # public key
166 if ( $basepoint eq pack('H64', '09') ) {
167 print "\$key is a public key\n";
168 }
169 elsif ( $basepoint eq $his_public_key ) {
170 print "\$key is a shared secret\n";
171 }
172 Using provided secret key and depending on the 32-byte basepoint
174 generate 32-byte public key or shared secret.
175
177 • <http://cr.yp.to/ecdh.html>
178
180 Alex J. G. Burzyński <ajgb@cpan.org>
181
183 This software is copyright (c) 2014 by Alex J. G. Burzyński
184 <ajgb@cpan.org>.
185 This is free software; you can redistribute it and/or modify it under
187 the same terms as the Perl 5 programming language system itself.
188perl v5.34.0 2022-03-04 Crypt::Curve25519(3)