really still wip

User/lib/ed25519/verify.c

@@ -75,3 +75,38 @@ int ed25519_verify(const unsigned char *signature, const unsigned char *message,
 
     return 1;
 }
+
+
+int ed25519_verify_ad(const FrameStruct *frame) {
+    unsigned char h[64];
+    unsigned char checker[32];
+    sha512_context hash;
+    ge_p3 A;
+    ge_p2 R;
+    const unsigned char *signature = &(frame->payload[36]);
+
+    if (signature[63] & 224) {
+        return 0;
+    }
+
+    if (ge_frombytes_negate_vartime(&A, frame->payload) != 0) { //pubkey is at start
+        return 0;
+    }
+
+    sha512_init(&hash);
+    sha512_update(&hash, signature, 32);
+    sha512_update(&hash, frame->payload, 32);
+    sha512_update(&hash, frame->payload, 36); // pubkey and timestamp combined (32 bytes pubkey, 4 bytes timestamp)
+    sha512_update(&hash, &(frame->payload[100]), frame->payloadLen - 100);
+    sha512_final(&hash, h);
+    
+    sc_reduce(h);
+    ge_double_scalarmult_vartime(&R, h, &A, signature + 32);
+    ge_tobytes(checker, &R);
+
+    if (!consttime_equal(checker, signature)) {
+        return 0;
+    }
+
+    return 1;
+}