lnrpc: update description for VerifyMessage

Fixes #3596.

lnrpc/lightning_grpc.pb.go

@@ -73,8 +73,10 @@ type LightningClient interface {
 	// only the message digest and signature are needed for verification.
 	SignMessage(ctx context.Context, in *SignMessageRequest, opts ...grpc.CallOption) (*SignMessageResponse, error)
 	// lncli: `verifymessage`
-	// VerifyMessage verifies a signature over a msg. The signature must be
-	// zbase32 encoded and signed by an active node in the resident node's
+	// VerifyMessage verifies a signature over a message and recovers the signer's
+	// public key. The signature is only deemed valid if the recovered public key
+	// corresponds to a node key in the public Lightning network. The signature
+	// must be zbase32 encoded and signed by an active node in the resident node's
 	// channel database. In addition to returning the validity of the signature,
 	// VerifyMessage also returns the recovered pubkey from the signature.
 	VerifyMessage(ctx context.Context, in *VerifyMessageRequest, opts ...grpc.CallOption) (*VerifyMessageResponse, error)
@@ -1375,8 +1377,10 @@ type LightningServer interface {
 	// only the message digest and signature are needed for verification.
 	SignMessage(context.Context, *SignMessageRequest) (*SignMessageResponse, error)
 	// lncli: `verifymessage`
-	// VerifyMessage verifies a signature over a msg. The signature must be
-	// zbase32 encoded and signed by an active node in the resident node's
+	// VerifyMessage verifies a signature over a message and recovers the signer's
+	// public key. The signature is only deemed valid if the recovered public key
+	// corresponds to a node key in the public Lightning network. The signature
+	// must be zbase32 encoded and signed by an active node in the resident node's
 	// channel database. In addition to returning the validity of the signature,
 	// VerifyMessage also returns the recovered pubkey from the signature.
 	VerifyMessage(context.Context, *VerifyMessageRequest) (*VerifyMessageResponse, error)