Draft implementation for ed25519 key blinding, as in prop224

This implementation allows somebody to add a blinding factor to a
secret key, and a corresponding blinding factor to the public key.

Robert Ransom came up with this idea, I believe.  Nick Hopper proved a
scheme like this secure.  The bugs are my own.

1 files changed, 6 insertions, 1 deletions

diff --git a/src/common/crypto_ed25519.h b/src/common/crypto_ed25519.h
index 82c5e6c6e3..1271312dfe 100644
--- a/src/common/crypto_ed25519.h
+++ b/src/common/crypto_ed25519.h
@@ -75,6 +75,12 @@ int ed25519_keypair_from_curve25519_keypair(ed25519_keypair_t *out,
 int ed25519_public_key_from_curve25519_public_key(ed25519_public_key_t *pubkey,
                                      const curve25519_public_key_t *pubkey_in,
                                      int signbit);
+int ed25519_keypair_blind(ed25519_keypair_t *out,
+                          const ed25519_keypair_t *inp,
+                          const uint8_t *param);
+int ed25519_public_blind(ed25519_public_key_t *out,
+                         const ed25519_public_key_t *inp,
+                         const uint8_t *param);
 
 #endif
 
@@ -100,6 +106,5 @@ int ed25519_pubkey_read_from_file(ed25519_public_key_t *pubkey_out,
                                   char **tag_out,
                                   const char *filename);
 
-
 #endif