From a1ce2e116f3a1cedeee1aa28fa8c7f20930ac66c Mon Sep 17 00:00:00 2001
From: Dave Collins <davec@conformal.com>
Date: Wed, 4 Aug 2021 03:52:55 -0500
Subject: [PATCH] secp256k1: Use blake256 directly in examples.

This modifies the ecdsa and schnorr examples to call blake256 directly
instead of indirecting through chainhash in order to avoid the chainhash
dependency which is otherwise not needed.

The go.mod and go.sum files are updated accordingly to remove the
no longer required dependency.
---
 dcrec/secp256k1/ecdsa/example_test.go   | 14 +++++++-------
 dcrec/secp256k1/go.mod                  |  5 +----
 dcrec/secp256k1/go.sum                  |  2 --
 dcrec/secp256k1/schnorr/example_test.go | 14 +++++++-------
 4 files changed, 15 insertions(+), 20 deletions(-)

diff --git a/dcrec/secp256k1/ecdsa/example_test.go b/dcrec/secp256k1/ecdsa/example_test.go
index 6b93096d..55ef738f 100644
--- a/dcrec/secp256k1/ecdsa/example_test.go
+++ b/dcrec/secp256k1/ecdsa/example_test.go
@@ -1,5 +1,5 @@
 // Copyright (c) 2014 The btcsuite developers
-// Copyright (c) 2015-2020 The Decred developers
+// Copyright (c) 2015-2021 The Decred developers
 // Use of this source code is governed by an ISC
 // license that can be found in the LICENSE file.
 
@@ -9,7 +9,7 @@ import (
 	"encoding/hex"
 	"fmt"
 
-	"github.com/decred/dcrd/chaincfg/chainhash"
+	"github.com/decred/dcrd/crypto/blake256"
 	"github.com/decred/dcrd/dcrec/secp256k1/v4"
 	"github.com/decred/dcrd/dcrec/secp256k1/v4/ecdsa"
 )
@@ -28,15 +28,15 @@ func ExampleSign() {
 
 	// Sign a message using the private key.
 	message := "test message"
-	messageHash := chainhash.HashB([]byte(message))
-	signature := ecdsa.Sign(privKey, messageHash)
+	messageHash := blake256.Sum256([]byte(message))
+	signature := ecdsa.Sign(privKey, messageHash[:])
 
 	// Serialize and display the signature.
 	fmt.Printf("Serialized Signature: %x\n", signature.Serialize())
 
 	// Verify the signature for the message using the public key.
 	pubKey := privKey.PubKey()
-	verified := signature.Verify(messageHash, pubKey)
+	verified := signature.Verify(messageHash[:], pubKey)
 	fmt.Printf("Signature Verified? %v\n", verified)
 
 	// Output:
@@ -77,8 +77,8 @@ func ExampleSignature_Verify() {
 
 	// Verify the signature for the message using the public key.
 	message := "test message"
-	messageHash := chainhash.HashB([]byte(message))
-	verified := signature.Verify(messageHash, pubKey)
+	messageHash := blake256.Sum256([]byte(message))
+	verified := signature.Verify(messageHash[:], pubKey)
 	fmt.Println("Signature Verified?", verified)
 
 	// Output:
diff --git a/dcrec/secp256k1/go.mod b/dcrec/secp256k1/go.mod
index 344306de..d15095a8 100644
--- a/dcrec/secp256k1/go.mod
+++ b/dcrec/secp256k1/go.mod
@@ -2,7 +2,4 @@ module github.com/decred/dcrd/dcrec/secp256k1/v4
 
 go 1.13
 
-require (
-	github.com/decred/dcrd/chaincfg/chainhash v1.0.2
-	github.com/decred/dcrd/crypto/blake256 v1.0.0
-)
+require github.com/decred/dcrd/crypto/blake256 v1.0.0
diff --git a/dcrec/secp256k1/go.sum b/dcrec/secp256k1/go.sum
index b41490e3..1687242d 100644
--- a/dcrec/secp256k1/go.sum
+++ b/dcrec/secp256k1/go.sum
@@ -1,4 +1,2 @@
-github.com/decred/dcrd/chaincfg/chainhash v1.0.2 h1:rt5Vlq/jM3ZawwiacWjPa+smINyLRN07EO0cNBV6DGU=
-github.com/decred/dcrd/chaincfg/chainhash v1.0.2/go.mod h1:BpbrGgrPTr3YJYRN3Bm+D9NuaFd+zGyNeIKgrhCXK60=
 github.com/decred/dcrd/crypto/blake256 v1.0.0 h1:/8DMNYp9SGi5f0w7uCm6d6M4OU2rGFK09Y2A4Xv7EE0=
 github.com/decred/dcrd/crypto/blake256 v1.0.0/go.mod h1:sQl2p6Y26YV+ZOcSTP6thNdn47hh8kt6rqSlvmrXFAc=
diff --git a/dcrec/secp256k1/schnorr/example_test.go b/dcrec/secp256k1/schnorr/example_test.go
index aaade57d..f0f4deee 100644
--- a/dcrec/secp256k1/schnorr/example_test.go
+++ b/dcrec/secp256k1/schnorr/example_test.go
@@ -1,4 +1,4 @@
-// Copyright (c) 2020 The Decred developers
+// Copyright (c) 2020-2021 The Decred developers
 // Use of this source code is governed by an ISC
 // license that can be found in the LICENSE file.
 
@@ -8,7 +8,7 @@ import (
 	"encoding/hex"
 	"fmt"
 
-	"github.com/decred/dcrd/chaincfg/chainhash"
+	"github.com/decred/dcrd/crypto/blake256"
 	"github.com/decred/dcrd/dcrec/secp256k1/v4"
 	"github.com/decred/dcrd/dcrec/secp256k1/v4/schnorr"
 )
@@ -28,8 +28,8 @@ func ExampleSign() {
 
 	// Sign a message using the private key.
 	message := "test message"
-	messageHash := chainhash.HashB([]byte(message))
-	signature, err := schnorr.Sign(privKey, messageHash)
+	messageHash := blake256.Sum256([]byte(message))
+	signature, err := schnorr.Sign(privKey, messageHash[:])
 	if err != nil {
 		fmt.Println(err)
 		return
@@ -40,7 +40,7 @@ func ExampleSign() {
 
 	// Verify the signature for the message using the public key.
 	pubKey := privKey.PubKey()
-	verified := signature.Verify(messageHash, pubKey)
+	verified := signature.Verify(messageHash[:], pubKey)
 	fmt.Printf("Signature Verified? %v\n", verified)
 
 	// Output:
@@ -81,8 +81,8 @@ func ExampleSignature_Verify() {
 
 	// Verify the signature for the message using the public key.
 	message := "test message"
-	messageHash := chainhash.HashB([]byte(message))
-	verified := signature.Verify(messageHash, pubKey)
+	messageHash := blake256.Sum256([]byte(message))
+	verified := signature.Verify(messageHash[:], pubKey)
 	fmt.Println("Signature Verified?", verified)
 
 	// Output: