keychain: add new abstraction interfaces

keychain/derivation.go

@@ -167,8 +167,8 @@ type KeyRing interface {
 	DeriveKey(keyLoc KeyLocator) (KeyDescriptor, error)
 }
 
-// SecretKeyRing is a similar to the regular KeyRing interface, but it is also
+// SecretKeyRing is a ring similar to the regular KeyRing interface, but it is
-// able to derive *private keys*. As this is a super-set of the regular
+// also able to derive *private keys*. As this is a super-set of the regular
 // KeyRing, we also expect the SecretKeyRing to implement the fully KeyRing
 // interface. The methods in this struct may be used to extract the node key in
 // order to accept inbound network connections, or to do manual signing for
@@ -194,5 +194,63 @@ type SecretKeyRing interface {
 	ScalarMult(keyDesc KeyDescriptor, pubKey *btcec.PublicKey) ([]byte, error)
 }
 
+// DigestSignerRing is an interface that abstracts away basic low-level ECDSA
+// signing on keys within a key ring.
+type DigestSignerRing interface {
+	// SignDigest signs the given SHA256 message digest with the private key
+	// described in the key descriptor.
+	SignDigest(keyDesc KeyDescriptor, digest [32]byte) (*btcec.Signature,
+		error)
+
+	// SignDigestCompact signs the given SHA256 message digest with the
+	// private key described in the key descriptor and returns the signature
+	// in the compact, public key recoverable format.
+	SignDigestCompact(keyDesc KeyDescriptor, digest [32]byte) ([]byte, error)
+}
+
+// SingleKeyDigestSigner is an abstraction interface that hides the
+// implementation of the low-level ECDSA signing operations by wrapping a
+// single, specific private key.
+type SingleKeyDigestSigner interface {
+	// PubKey returns the public key of the wrapped private key.
+	PubKey() *btcec.PublicKey
+
+	// SignDigest signs the given SHA256 message digest with the wrapped
+	// private key.
+	SignDigest(digest [32]byte) (*btcec.Signature, error)
+
+	// SignDigestCompact signs the given SHA256 message digest with the
+	// wrapped private key and returns the signature in the compact, public
+	// key recoverable format.
+	SignDigestCompact(digest [32]byte) ([]byte, error)
+}
+
+// ECDHRing is an interface that abstracts away basic low-level ECDH shared key
+// generation on keys within a key ring.
+type ECDHRing interface {
+	// ECDH performs a scalar multiplication (ECDH-like operation) between
+	// the target key descriptor and remote public key. The output
+	// returned will be the sha256 of the resulting shared point serialized
+	// in compressed format. If k is our private key, and P is the public
+	// key, we perform the following operation:
+	//
+	//  sx := k*P
+	//  s := sha256(sx.SerializeCompressed())
+	ECDH(keyDesc KeyDescriptor, pubKey *btcec.PublicKey) ([32]byte, error)
+}
+
+// SingleKeyECDH is an abstraction interface that hides the implementation of an
+// ECDH operation by wrapping a single, specific private key.
+type SingleKeyECDH interface {
+	// PubKey returns the public key of the wrapped private key.
+	PubKey() *btcec.PublicKey
+
+	// ECDH performs a scalar multiplication (ECDH-like operation) between
+	// the wrapped private key and remote public key. The output returned
+	// will be the sha256 of the resulting shared point serialized in
+	// compressed format.
+	ECDH(pubKey *btcec.PublicKey) ([32]byte, error)
+}
+
 // TODO(roasbeef): extend to actually support scalar mult of key?
 //  * would allow to push in initial handshake auth into interface as well