com.google.bitcoin.crypto.DeterministicKey Maven / Gradle / Ivy
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/**
* Copyright 2013 Matija Mazi.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.bitcoin.crypto;
import com.google.bitcoin.core.Base58;
import com.google.bitcoin.core.ECKey;
import com.google.bitcoin.core.Utils;
import com.google.common.base.Joiner;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import org.spongycastle.math.ec.ECPoint;
import org.spongycastle.util.encoders.Hex;
import javax.annotation.Nullable;
import java.io.Serializable;
import java.math.BigInteger;
import java.nio.ByteBuffer;
import java.text.MessageFormat;
import java.util.Arrays;
import java.util.Collections;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
// TODO: Merge this with a redesigned ECKey class.
/**
* A deterministic key is a node in a {@link DeterministicHierarchy}. As per
* the BIP 32 specification it is a pair (key, chaincode). If you
* know its path in the tree you can derive more keys from this.
*/
public class DeterministicKey implements Serializable {
private static final long serialVersionUID = 1L;
private static final Joiner PATH_JOINER = Joiner.on("/");
private final DeterministicKey parent;
private ECPoint publicAsPoint;
private final BigInteger privateAsFieldElement;
private final ImmutableList childNumberPath;
/** 32 bytes */
private final byte[] chainCode;
DeterministicKey(ImmutableList childNumberPath, byte[] chainCode,
@Nullable ECPoint publicAsPoint, @Nullable BigInteger privateKeyFieldElt,
@Nullable DeterministicKey parent) {
checkArgument(chainCode.length == 32);
this.parent = parent;
this.childNumberPath = childNumberPath;
this.chainCode = Arrays.copyOf(chainCode, chainCode.length);
this.publicAsPoint = publicAsPoint == null ? null : HDUtils.compressedCopy(publicAsPoint);
this.privateAsFieldElement = privateKeyFieldElt;
}
/**
* Returns the path through some {@link DeterministicHierarchy} which reaches this keys position in the tree.
* A path can be written as 1/2/1 which means the first child of the root, the second child of that node, then
* the first child of that node.
*/
public ImmutableList getChildNumberPath() {
return childNumberPath;
}
private int getDepth() {
return childNumberPath.size();
}
/**
* Returns the last element of the path returned by {@link DeterministicKey#getChildNumberPath()}
*/
public ChildNumber getChildNumber() {
return getDepth() == 0 ? ChildNumber.ZERO : childNumberPath.get(childNumberPath.size() - 1);
}
/**
* Returns the chain code associated with this key. See the specification to learn more about chain codes.
*/
public byte[] getChainCode() {
return chainCode;
}
/**
* Returns the path of this key as a human readable string starting with M to indicate the master key.
*/
public String getPath() {
return PATH_JOINER.join(Iterables.concat(Collections.singleton("M"), getChildNumberPath()));
}
/**
* Returns RIPE-MD160(SHA256(pub key bytes)).
*/
public byte[] getIdentifier() {
return Utils.sha256hash160(getPubKeyBytes());
}
ECPoint getPubPoint() {
if (publicAsPoint == null) {
checkNotNull(privateAsFieldElement);
publicAsPoint = ECKey.CURVE.getG().multiply(privateAsFieldElement);
}
return HDUtils.compressedCopy(publicAsPoint);
}
public byte[] getPubKeyBytes() {
return getPubPoint().getEncoded();
}
/** Returns the first 32 bits of the result of {@link #getIdentifier()}. */
public byte[] getFingerprint() {
// TODO: why is this different than armory's fingerprint? BIP 32: "The first 32 bits of the identifier are called the fingerprint."
return Arrays.copyOfRange(getIdentifier(), 0, 4);
}
@Nullable
public BigInteger getPrivAsFieldElement() {
return privateAsFieldElement;
}
@Nullable
public DeterministicKey getParent() {
return parent;
}
/**
* Returns the private key bytes, if they were provided during construction.
*/
@Nullable
public byte[] getPrivKeyBytes() {
return privateAsFieldElement == null ? null : privateAsFieldElement.toByteArray();
}
/**
* @return private key bytes, padded with zeros to 33 bytes.
*/
public byte[] getPrivKeyBytes33() {
byte[] bytes33 = new byte[33];
byte[] priv = checkNotNull(getPrivKeyBytes(), "Private key missing");
System.arraycopy(priv, 0, bytes33, 33 - priv.length, priv.length);
return bytes33;
}
/**
* Returns the same key with the private part removed. May return the same instance.
*/
public DeterministicKey getPubOnly() {
if (!hasPrivate()) return this;
final DeterministicKey parentPub = getParent() == null ? null : getParent().getPubOnly();
return new DeterministicKey(getChildNumberPath(), getChainCode(), getPubPoint(), null, parentPub);
}
public boolean hasPrivate() {
return privateAsFieldElement != null;
}
public ECKey toECKey() {
return new ECKey(getPrivKeyBytes(), getPubKeyBytes());
}
public String serializePubB58() {
return toBase58(serialize(true));
}
public String serializePrivB58() {
return toBase58(serialize(false));
}
static String toBase58(byte[] ser) {
return Base58.encode(addChecksum(ser));
}
static byte[] addChecksum(byte[] input) {
int inputLength = input.length;
byte[] checksummed = new byte[inputLength + 4];
System.arraycopy(input, 0, checksummed, 0, inputLength);
byte[] checksum = Utils.doubleDigest(input);
System.arraycopy(checksum, 0, checksummed, inputLength, 4);
return checksummed;
}
public byte[] serializePublic() {
return serialize(true);
}
public byte[] serializePrivate() {
return serialize(false);
}
private byte[] serialize(boolean pub) {
ByteBuffer ser = ByteBuffer.allocate(78);
ser.putInt(pub ? 0x0488B21E : 0x0488ADE4);
ser.put((byte) getDepth());
if (parent == null) {
ser.putInt(0);
} else {
ser.put(parent.getFingerprint());
}
ser.putInt(getChildNumber().getI());
ser.put(getChainCode());
ser.put(pub ? getPubKeyBytes() : getPrivKeyBytes33());
assert ser.position() == 78;
return ser.array();
}
@Override
public String toString() {
return MessageFormat.format("ExtendedHierarchicKey[pub: {0}]", new String(Hex.encode(getPubKeyBytes())));
}
}