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fix child keys derivation adding bytes padding #1139

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merged 6 commits into from Sep 4, 2018
Merged

fix child keys derivation adding bytes padding #1139

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5a5328a
add bytes padding in derived keys
gravityblast Aug 6, 2018
19d1bed
add 3rd test vector taken from BIP32 specs
gravityblast Aug 9, 2018
ac3e8b0
test specific case where keyData is less then 32 bytes
gravityblast Aug 9, 2018
a55d387
add comment on key data padding snippet
gravityblast Aug 9, 2018
edd3416
add more docs comments
gravityblast Aug 10, 2018
69f0b15
Merge branch 'develop' into fix/bip32-keys-derivation
gravityblast Aug 13, 2018
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8 changes: 7 additions & 1 deletion extkeys/hdkey.go
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Expand Up @@ -194,7 +194,13 @@ func (k *ExtendedKey) Child(i uint32) (*ExtendedKey, error) {
keyBigInt.Add(keyBigInt, parentKeyBigInt)
keyBigInt.Mod(keyBigInt, btcec.S256().N)

child.KeyData = keyBigInt.Bytes()
keyData := keyBigInt.Bytes()
if len(keyData) < 32 {
extra := make([]byte, 32-len(keyData))
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if you want you could do a single allocation instead of 2

extra := make([]byte, 32-len, 32)

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@dmitryn yes good point I'll do it!

keyData = append(extra, keyData...)
}

child.KeyData = keyData
child.Version = PrivateKeyVersion
} else {
// Case #3: childKey = serP(point(parse256(IL)) + parentKey)
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15 changes: 15 additions & 0 deletions extkeys/hdkey_test.go
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Expand Up @@ -111,6 +111,21 @@ func TestBIP32Vectors(t *testing.T) {
"xpub6FnCn6nSzZAw5Tw7cgR9bi15UV96gLZhjDstkXXxvCLsUXBGXPdSnLFbdpq8p9HmGsApME5hQTZ3emM2rnY5agb9rXpVGyy3bdW6EEgAtqt",
"xprvA2nrNbFZABcdryreWet9Ea4LvTJcGsqrMzxHx98MMrotbir7yrKCEXw7nadnHM8Dq38EGfSh6dqA9QWTyefMLEcBYJUuekgW4BYPJcr9E7j",
},
// Test vector 3
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can you reference where this came from for future folks looking at this?

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good point @corpetty, I'm adding it to the PR description, it's from here:

https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki#test-vector-3

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PR descriptions/commit messages are pretty ephemeral. Let's put all the references in the code so no refactorings can destroy it!

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@mandrigin I added more comments in the code taken from the PR description

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hey @mandrigin @corpetty is there anything else you want to change in this PR?

{
"test vector 3 chain m",
"4b381541583be4423346c643850da4b320e46a87ae3d2a4e6da11eba819cd4acba45d239319ac14f863b8d5ab5a0d0c64d2e8a1e7d1457df2e5a3c51c73235be",
[]uint32{},
"xpub661MyMwAqRbcEZVB4dScxMAdx6d4nFc9nvyvH3v4gJL378CSRZiYmhRoP7mBy6gSPSCYk6SzXPTf3ND1cZAceL7SfJ1Z3GC8vBgp2epUt13",
"xprv9s21ZrQH143K25QhxbucbDDuQ4naNntJRi4KUfWT7xo4EKsHt2QJDu7KXp1A3u7Bi1j8ph3EGsZ9Xvz9dGuVrtHHs7pXeTzjuxBrCmmhgC6",
},
{
"test vector 3 chain m/0H",
"4b381541583be4423346c643850da4b320e46a87ae3d2a4e6da11eba819cd4acba45d239319ac14f863b8d5ab5a0d0c64d2e8a1e7d1457df2e5a3c51c73235be",
[]uint32{HardenedKeyStart},
"xpub68NZiKmJWnxxS6aaHmn81bvJeTESw724CRDs6HbuccFQN9Ku14VQrADWgqbhhTHBaohPX4CjNLf9fq9MYo6oDaPPLPxSb7gwQN3ih19Zm4Y",
"xprv9uPDJpEQgRQfDcW7BkF7eTya6RPxXeJCqCJGHuCJ4GiRVLzkTXBAJMu2qaMWPrS7AANYqdq6vcBcBUdJCVVFceUvJFjaPdGZ2y9WACViL4L",
},
}

tests:
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