Update libsecp256k1

crypto/secp256k1/libsecp256k1/include/secp256k1_ecdh.h

@@ -0,0 +1,30 @@
+#ifndef _SECP256K1_ECDH_
+# define _SECP256K1_ECDH_
+
+# include "secp256k1.h"
+
+# ifdef __cplusplus
+extern "C" {
+# endif
+
+/** Compute an EC Diffie-Hellman secret in constant time
+ *  Returns: 1: exponentiation was successful
+ *           0: scalar was invalid (zero or overflow)
+ *  Args:    ctx:      pointer to a context object (cannot be NULL)
+ *  Out:     result:   a 32-byte array which will be populated by an ECDH
+ *                     secret computed from the point and scalar
+ *  In:      point:    pointer to a public point
+ *           scalar:   a 32-byte scalar with which to multiply the point
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ecdh(
+  const secp256k1_context* ctx,
+  unsigned char *result,
+  const secp256k1_pubkey *point,
+  const unsigned char *scalar
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
+
+# ifdef __cplusplus
+}
+# endif
+
+#endif