Implemented X25519 generateKeys and fromEd25519 functions

src/crypto/x25519.zig

@@ -1,13 +1,39 @@
-//TODO
+// Errors
+const CryptoError = @import("../crypto.zig").CryptoError;
+// Constants and default implementation
+const X25519 = @import("std").crypto.dh.X25519;
+const Ed25519 = @import("std").crypto.sign.Ed25519;
+// Random number generation
+const rngProvider = @import("random.zig").Implementation;
 
-const X25519 = @import("std").std.crypto.dh.X25519;
+pub const secret_key_length: comptime_int = X25519.secret_length;
+pub const public_key_length: comptime_int = X25519.public_length;
+pub const seed_length: comptime_int = X25519.seed_length;
 
 pub const Implementation = struct {
     
+    generateKeys: *const fn (pubkey_buffer: ?*[public_key_length]u8, privkey_buffer: *[secret_key_length]u8, rng: rngProvider) CryptoError!void,
+    fromEd25519: *const fn (ed25519_keypair: *Ed25519.Keypair, x25519_keypair: *X25519.KeyPair, rng: rngProvider) CryptoError!void,
+    // TODO
+    // maybe switch to a Keypair system based on the stdlib implementation
+    // generateKeys: *const fn (keypair: *X25519.KeyPair, rng: rngProvider) CryptoError!void,
 };
 
+fn generateKeys (pubkey_buffer: ?*[public_key_length]u8, privkey_buffer: *[secret_key_length]u8, rng: rngProvider) !void {
+    
+    var seed_buffer: [seed_length]u8 = undefined;
+    rng.generate(&seed_buffer);
+    const keypair: X25519.KeyPair = X25519.KeyPair.generateDeterministic(seed_buffer) catch return CryptoError.FailedKeyGeneration;
+    
+    if (pubkey_buffer != null) @memcpy(pubkey_buffer.?[0..public_key_length], &keypair.public_key.bytes);
+    @memcpy(privkey_buffer[0..secret_key_length], &keypair.secret_key.bytes);
+}
+
+fn fromEd25519 (ed25519_keypair: *Ed25519.Keypair, x25519_keypair: *X25519.KeyPair) CryptoError!void {
+    x25519_keypair.* = X25519.KeyPair.fromEd25519(ed25519_keypair);
+}
+
 pub const defaultImplementation: Implementation = .{
-
+    .generateKeys = generateKeys,
-    // One problem, it uses the zig's io module, which is not supported yet as it depends on the target OS
+    .fromEd25519 = fromEd25519,
-    // It may need a custom implementation or some other library
 };