Deterministic signing

src/key.h

@@ -121,8 +121,12 @@ public:
      */
     CPubKey GetPubKey() const;
 
-    //! Create a DER-serialized signature.
-    bool Sign(const uint256& hash, std::vector<unsigned char>& vchSig) const;
+    /**
+     * Create a DER-serialized signature.
+     * The test_case parameter tweaks the deterministic nonce, and is only for
+     * testing. It should be zero for normal use.
+     */
+    bool Sign(const uint256& hash, std::vector<unsigned char>& vchSig, uint32_t test_case = 0) const;
 
     /**
      * Create a compact signature (65 bytes), which allows reconstructing the used public key.