From d174393ebc42e37e7b4031a75b3af9149eca8b9f Mon Sep 17 00:00:00 2001
From: Anton Astafiev <anton.astafiev@dfinity.org>
Date: Tue, 20 Apr 2021 17:26:14 +0200
Subject: [PATCH] Move change inside crypto.go

---
 cmd/account.go        | 10 +++-------
 cmd/legacy-address.go | 10 +++-------
 cmd/principal.go      | 10 +++-------
 cmd/private-key.go    | 10 +++-------
 cmd/public-key.go     | 10 +++-------
 crypto/crypto.go      |  7 ++++++-
 6 files changed, 21 insertions(+), 36 deletions(-)

diff --git a/cmd/account.go b/cmd/account.go
index 273a940..5134bbb 100644
--- a/cmd/account.go
+++ b/cmd/account.go
@@ -43,18 +43,14 @@ func (cmd *AccountCmd) Run() error {
 	if err != nil {
 		return err
 	}
-	childXPrivKey, err := masterXPrivKey.Derive(0)
-	if err != nil {
-		return err
-	}
-	_, grandchildECPubKey, err := crypto.DeriveChildECKeyPair(
-		childXPrivKey,
+	_, childECPubKey, err := crypto.DeriveChildECKeyPair(
+		masterXPrivKey,
 		uint32(*cmd.Args.Index),
 	)
 	if err != nil {
 		return err
 	}
-	accountId, err := account.FromECPubKey(grandchildECPubKey)
+	accountId, err := account.FromECPubKey(childECPubKey)
 	if err != nil {
 		return err
 	}
diff --git a/cmd/legacy-address.go b/cmd/legacy-address.go
index a8494fb..e584e21 100644
--- a/cmd/legacy-address.go
+++ b/cmd/legacy-address.go
@@ -44,18 +44,14 @@ func (cmd *LegacyAddressCmd) Run() error {
 	if err != nil {
 		return err
 	}
-	childXPrivKey, err := masterXPrivKey.Derive(0)
-	if err != nil {
-		return err
-	}
-	_, grandchildECPubKey, err := crypto.DeriveChildECKeyPair(
-		childXPrivKey,
+	_, childECPubKey, err := crypto.DeriveChildECKeyPair(
+		masterXPrivKey,
 		uint32(*cmd.Args.Index),
 	)
 	if err != nil {
 		return err
 	}
-	address := eth.PubkeyToAddress(*grandchildECPubKey.ToECDSA())
+	address := eth.PubkeyToAddress(*childECPubKey.ToECDSA())
 	output := strings.ToLower(strings.TrimPrefix(address.String(), "0x"))
 	fmt.Println(output)
 	return nil
diff --git a/cmd/principal.go b/cmd/principal.go
index aec866d..79aca41 100644
--- a/cmd/principal.go
+++ b/cmd/principal.go
@@ -43,18 +43,14 @@ func (cmd *PrincipalCmd) Run() error {
 	if err != nil {
 		return err
 	}
-	childXPrivKey, err := masterXPrivKey.Derive(0)
-	if err != nil {
-		return err
-	}
-	_, grandchildECPubKey, err := crypto.DeriveChildECKeyPair(
-		childXPrivKey,
+	_, childECPubKey, err := crypto.DeriveChildECKeyPair(
+		masterXPrivKey,
 		uint32(*cmd.Args.Index),
 	)
 	if err != nil {
 		return err
 	}
-	principalId, err := principal.FromECPubKey(grandchildECPubKey)
+	principalId, err := principal.FromECPubKey(childECPubKey)
 	if err != nil {
 		return err
 	}
diff --git a/cmd/private-key.go b/cmd/private-key.go
index 3c05d19..a786901 100644
--- a/cmd/private-key.go
+++ b/cmd/private-key.go
@@ -53,18 +53,14 @@ func (cmd *PrivateKeyCmd) Run() error {
 	if err != nil {
 		return err
 	}
-	childXPrivKey, err := masterXPrivKey.Derive(0)
-	if err != nil {
-		return err
-	}
-	grandchildECPrivKey, _, err := crypto.DeriveChildECKeyPair(
-		childXPrivKey,
+	childECPrivKey, _, err := crypto.DeriveChildECKeyPair(
+		masterXPrivKey,
 		uint32(*cmd.Args.Index),
 	)
 	if err != nil {
 		return err
 	}
-	output, err := codec.ECPrivKeyToPEM(grandchildECPrivKey)
+	output, err := codec.ECPrivKeyToPEM(childECPrivKey)
 	if err != nil {
 		return err
 	}
diff --git a/cmd/public-key.go b/cmd/public-key.go
index c587f60..8a23f22 100644
--- a/cmd/public-key.go
+++ b/cmd/public-key.go
@@ -43,18 +43,14 @@ func (cmd *PublicKeyCmd) Run() error {
 	if err != nil {
 		return err
 	}
-	childXPrivKey, err := masterXPrivKey.Derive(0)
-	if err != nil {
-		return err
-	}
-	_, grandchildECPubKey, err := crypto.DeriveChildECKeyPair(
-		childXPrivKey,
+	_, childECPubKey, err := crypto.DeriveChildECKeyPair(
+		masterXPrivKey,
 		uint32(*cmd.Args.Index),
 	)
 	if err != nil {
 		return err
 	}
-	output := hex.EncodeToString(grandchildECPubKey.SerializeUncompressed())
+	output := hex.EncodeToString(childECPubKey.SerializeUncompressed())
 	fmt.Println(output)
 	return nil
 }
diff --git a/crypto/crypto.go b/crypto/crypto.go
index f5904b1..562a248 100644
--- a/crypto/crypto.go
+++ b/crypto/crypto.go
@@ -34,7 +34,12 @@ func DeriveChildECKeyPair(
 	masterXPrivKey *hdkeychain.ExtendedKey,
 	i uint32,
 ) (*btcec.PrivateKey, *btcec.PublicKey, error) {
-	childXPrivKey, err := masterXPrivKey.Derive(i)
+	// First apply the change.
+	childXPrivKey, err := masterXPrivKey.Derive(0)
+	if err != nil {
+                return nil, nil, err
+        }
+	childXPrivKey, err = childXPrivKey.Derive(i)
 	if err != nil {
 		return nil, nil, err
 	}