ADDED: Public key signatures and signature verification with Ed25519

src/prolog/lib/crypto.pl

@@ -9,7 +9,7 @@
    and strings have the advantage that the atom table remains unmodified.
 
    Especially for cryptographic applications, it as an advantage that
-   using strings leaves little trace of what was processed in the system,
+   using strings leaves little trace of what was processed in the system.
 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 
 :- module(crypto,
@@ -21,6 +21,8 @@
            crypto_password_hash/3,     % +Password, -Hash, +Options
            crypto_data_encrypt/6,      % +PlainText, +Algorithm, +Key, +IV, -CipherText, +Options
            crypto_data_decrypt/6,      % +CipherText, +Algorithm, +Key, +IV, -PlainText, +Options
+           ed25519_sign/4,             % +PrivateKey, +Data, -Signature, +Options
+           ed25519_verify/4,           % +PublicKey, +Data, -Signature, +Options
            crypto_name_curve/2,        % +Name, -Curve
            crypto_curve_order/2,       % +Curve, -Order
            crypto_curve_generator/2,   % +Curve, -Generator
@@ -624,6 +626,44 @@ encoding_bytes(utf8, Cs, Bs) :-
         ;   domain_error(encryption_encoding, Cs, crypto)
         ).
 
+/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   Digital signatures with Ed25519
+   ===============================
+
+   ed25519_sign(+Key, +Data, -Signature, +Options)
+
+   Key and Data must be lists of characters. Key is a private key in
+   PKCS#8 (v1 or v2) DER format. Sign Data with Key, yielding
+   Signature as a list of hexadecimal characters.
+
+
+   ed25519_verify(+Key, +Data, +Signature, +Options)
+
+   Key and Data must be lists of characters. Key is a public key in
+   PKCS#8 DER format. Succeeds if Data was signed with the private key
+   corresponding to Key, where Signature is a list of hexadecimal
+   characters as generated by ed25519_sign/4. Fails otherwise.
+
+
+   Currently, the only option for both predicates is:
+
+     - encoding(+Encoding)
+       The default encoding of Data is utf8. The alternative is octet,
+       which treats Data as a list of raw bytes.
+- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
+
+ed25519_sign(Key0, Data0, Signature, Options) :-
+        options_data_bytes(Options, Data0, Data),
+        encoding_bytes(octet, Key0, Key),
+        '$ed25519_sign'(Key, Data, Signature0),
+        hex_bytes(Signature, Signature0).
+
+ed25519_verify(Key0, Data0, Signature0, Options) :-
+        options_data_bytes(Options, Data0, Data),
+        encoding_bytes(octet, Key0, Key),
+        hex_bytes(Signature0, Signature),
+        '$ed25519_verify'(Key, Data, Signature).
+
 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    Modular multiplicative inverse.