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Add support for extended BIP32 #13

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Add support for extended BIP32 #13

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48 changes: 25 additions & 23 deletions src/Bip32.mo
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@ module {
public type Path = {
#text : Text;
#array : [Nat32];
#extended: [[Nat8]];
};

// #publicKeyData is SEC1 encoded public key data.
Expand Down Expand Up @@ -106,7 +107,9 @@ module {
if (not Affine.isOnCurve(parsedPoint)) {
return null;
};
?ExtendedPublicKey(keyData, chaincode, depth, index, parentPubKey);
let indexBytes = Array.init<Nat8>(4, 0x00);
Common.writeBE32(indexBytes, 0, index);
?ExtendedPublicKey(keyData, chaincode, depth, Array.freeze(indexBytes), parentPubKey);
};
};
};
Expand All @@ -117,8 +120,15 @@ module {
};
};

func isHardenedIndex(index: Nat32) : Bool {
return index >= 0x80000000; // 2**31
func arrayPathFromNat32(path: [Nat32]) : [[Nat8]] {
let extendedPath : Buffer.Buffer<[Nat8]> = Buffer.Buffer(path.size());
for (idx in path.vals()) {
let indexBytes : [var Nat8] = Array.init<Nat8>(4, 0x00);
Common.writeBE32(indexBytes, 0, idx);
extendedPath.add(Array.freeze(indexBytes));
};

return extendedPath.toArray();
};

// Parses a Text path in the form "m/a/b/c/..." for unsigned integers
Expand Down Expand Up @@ -167,7 +177,7 @@ module {
_key: [Nat8],
_chaincode : [Nat8],
_depth: Nat8,
_index: Nat32,
_index: [Nat8],
_parentPublicKey: ?ParentPublicKey
) {

Expand All @@ -182,12 +192,15 @@ module {
public func derivePath(path : Path) : ?ExtendedPublicKey {
return do ? {
// Normalize the given path as an array of indices.
let pathArray : [Nat32] = switch(path) {
let pathArray : [[Nat8]] = switch(path) {
case (#array path) {
arrayPathFromNat32(path);
};
case (#extended path) {
path
};
case (#text path) {
arrayPathFromString(path)!;
arrayPathFromNat32(arrayPathFromString(path)!);
};
};

Expand All @@ -202,22 +215,11 @@ module {
};
};

// Derive child at the given index. Valid indices are in the range
// [0, 2^31 - 1] and the function throws an error if given an index outside
// this range.
public func deriveChild(index: Nat32) : ?ExtendedPublicKey {
if (isHardenedIndex(index)) {
return null;
};

// Compute HMAC with chaincode as the key and the serialized
// parentPublicKey (33 bytes) concatenated with the serialized
// index (4 bytes) as its data.
let hmacData : [var Nat8] = Array.init<Nat8>(33 + 4, 0x00);
Common.copy(hmacData, 0, key, 0, 33);
Common.writeBE32(hmacData, 33, index);
// Derive child at the given index.
public func deriveChild(index: [Nat8]) : ?ExtendedPublicKey {
let hmacSha512 : Hmac.Hmac = Hmac.sha512(chaincode);
hmacSha512.write(Array.freeze(hmacData));
hmacSha512.write(key);
hmacSha512.write(index);
let fullNode : [Nat8] = hmacSha512.sum();

// Split HMAC output into two 32-byte sequences.
Expand Down Expand Up @@ -275,12 +277,12 @@ module {
result[4] := depth;
let fingerprint = Hash.hash160(parentPublicKey);
Common.copy(result, 5, fingerprint, 0, 4);
Common.writeBE32(result, 9, index);
Common.copy(result, 9, index, 0, 4);
};
case (?(#fingerprint fingerprint)) {
result[4] := depth;
Common.copy(result, 5, fingerprint, 0, 4);
Common.writeBE32(result, 9, index);
Common.copy(result, 9, index, 0, 4);
};
};
Common.copy(result, 13, chaincode, 0, 32);
Expand Down
8 changes: 0 additions & 8 deletions test/bip32Test.mo
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Original file line number Diff line number Diff line change
Expand Up @@ -43,10 +43,6 @@ let derivationVectors: [DerivationVector] = [
serialized = ?("xpub6FHUhLbYYkgFQiFrDiXRfQFXBB2msCxKTsNyAExi6keFxQ8sHfwpogY3p3s1"
# "ePSpUqLNYks5T6a3JqpCGszt4kxbyq7tUoFP5c8KWyiDtPp");
},
{
derivePath = #text "m/0/1'/2/2";
serialized = null;
},
{
derivePath = #text "m/0/1/2/2/1000000000";
serialized = ?("xpub6GX3zWVgSgPc5tgjE6ogT9nfwSADD3tdsxpzd7jJoJMqSY12Be6VQEFwDCp6"
Expand All @@ -68,10 +64,6 @@ let derivationVectors: [DerivationVector] = [
serialized = ?("xpub6ASAVgeWMg4pmutghzHG3BohahjwNwPmy2DgM6W9wGegtPrvNgjBwuZRD7hS"
# "DFhYfunq8vDgwG4ah1gVzZysgp3UsKz7VNjCnSUJJ5T4fdD");
},
{
derivePath = #array ([0, 2147483649]);
serialized = null;
},
{
derivePath = #array ([0, 2147483647, 1]);
serialized = ?("xpub6CrnV7NzJy4VdgP5niTpqWJiFXMAca6qBm5Hfsry77SQmN1HGYHnjsZSujoH"
Expand Down