1 files changed, 42 insertions, 0 deletions
diff --git a/src/ext/ed25519/ref10/open.c b/src/ext/ed25519/ref10/open.c
new file mode 100644
index 0000000000..9dbeb4cdd0
--- /dev/null
+++ b/src/ext/ed25519/ref10/open.c
@@ -0,0 +1,42 @@
+/* (Modified by Tor to verify signature separately from message) */
+#include <string.h>
+#include "crypto_sign.h"
+#include "crypto_hash_sha512.h"
+#include "crypto_verify_32.h"
+#include "ge.h"
+#include "sc.h"
+
+/* 'signature' must be 64-bytes long. */
+int crypto_sign_open(
+  const unsigned char *signature,
+  const unsigned char *m, size_t mlen,
+  const unsigned char *pk
+)
+{
+  unsigned char pkcopy[32];
+  unsigned char rcopy[32];
+  unsigned char scopy[32];
+  unsigned char h[64];
+  unsigned char rcheck[32];
+  ge_p3 A;
+  ge_p2 R;
+
+  if (signature[63] & 224) goto badsig;
+  if (ge_frombytes_negate_vartime(&A,pk) != 0) goto badsig;
+
+  memmove(pkcopy,pk,32);
+  memmove(rcopy,signature,32);
+  memmove(scopy,signature + 32,32);
+
+  crypto_hash_sha512_3(h, rcopy, 32, pkcopy, 32, m, mlen);
+  sc_reduce(h);
+
+  ge_double_scalarmult_vartime(&R,h,&A,scopy);
+  ge_tobytes(rcheck,&R);
+  if (crypto_verify_32(rcheck,rcopy) == 0) {
+    return 0;
+  }
+
+badsig:
+  return -1;
+}