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Switch to accelerated secp256k1: huge speed improvements.

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This commit is contained in:
Mike Hearn 2014-07-26 14:56:34 +02:00
parent 6ae4662f93
commit 539037ec0e
1 changed files with 11 additions and 10 deletions
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21
core/src/main/java/com/google/bitcoin/core/ECKey.java
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@ -27,18 +27,19 @@ import org.bitcoinj.wallet.Protos;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.spongycastle.asn1.*;
import org.spongycastle.asn1.sec.SECNamedCurves;
import org.spongycastle.asn1.x9.X9ECParameters;
import org.spongycastle.asn1.x9.X9IntegerConverter;
import org.spongycastle.crypto.AsymmetricCipherKeyPair;
import org.spongycastle.crypto.digests.SHA256Digest;
import org.spongycastle.crypto.ec.CustomNamedCurves;
import org.spongycastle.crypto.generators.ECKeyPairGenerator;
import org.spongycastle.crypto.params.*;
import org.spongycastle.crypto.signers.ECDSASigner;
import org.spongycastle.crypto.signers.HMacDSAKCalculator;
import org.spongycastle.math.ec.ECAlgorithms;
import org.spongycastle.math.ec.ECCurve;
import org.spongycastle.math.ec.ECPoint;
import org.spongycastle.math.ec.FixedPointUtil;
import org.spongycastle.math.ec.custom.sec.SecP256K1Curve;
import org.spongycastle.util.encoders.Base64;
import javax.annotation.Nullable;
@ -51,9 +52,7 @@ import java.security.SecureRandom;
import java.security.SignatureException;
import java.util.Arrays;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
import static com.google.common.base.Preconditions.*;
// TODO: Move this class to tracking compression state itself.
// The Bouncy Castle guys are deprecating their own tracking of the compression state.
@ -90,7 +89,7 @@ public class ECKey implements EncryptableItem, Serializable {
private static final Logger log = LoggerFactory.getLogger(ECKey.class);
/** The parameters of the secp256k1 curve that Bitcoin uses. */
public static final X9ECParameters CURVE_PARAMS = SECNamedCurves.getByName("secp256k1");
public static final X9ECParameters CURVE_PARAMS = CustomNamedCurves.getByName("secp256k1");
/** The parameters of the secp256k1 curve that Bitcoin uses. */
public static final ECDomainParameters CURVE;
@ -105,7 +104,10 @@ public class ECKey implements EncryptableItem, Serializable {
private static final long serialVersionUID = -728224901792295832L;
static {
// All clients must agree on the curve to use by agreement. Bitcoin uses secp256k1.
// Tell Bouncy Castle to precompute data that's needed during secp256k1 calculations. Increasing the width
// number makes calculations faster, but at a cost of extra memory usage and with decreasing returns. 12 was
// picked after consulting with the BC team.
FixedPointUtil.precompute(CURVE_PARAMS.getG(), 12);
CURVE = new ECDomainParameters(CURVE_PARAMS.getCurve(), CURVE_PARAMS.getG(), CURVE_PARAMS.getN(),
CURVE_PARAMS.getH());
HALF_CURVE_ORDER = CURVE_PARAMS.getN().shiftRight(1);
@ -837,8 +839,7 @@ public class ECKey implements EncryptableItem, Serializable {
// do another iteration of Step 1.
//
// More concisely, what these points mean is to use X as a compressed public key.
ECCurve.Fp curve = (ECCurve.Fp) CURVE.getCurve();
BigInteger prime = curve.getQ(); // Bouncy Castle is not consistent about the letter it uses for the prime.
BigInteger prime = SecP256K1Curve.q;
if (x.compareTo(prime) >= 0) {
// Cannot have point co-ordinates larger than this as everything takes place modulo Q.
return null;
@ -866,7 +867,7 @@ public class ECKey implements EncryptableItem, Serializable {
BigInteger rInv = sig.r.modInverse(n);
BigInteger srInv = rInv.multiply(sig.s).mod(n);
BigInteger eInvrInv = rInv.multiply(eInv).mod(n);
ECPoint.Fp q = (ECPoint.Fp) ECAlgorithms.sumOfTwoMultiplies(CURVE.getG(), eInvrInv, R, srInv);
ECPoint q = ECAlgorithms.sumOfTwoMultiplies(CURVE.getG(), eInvrInv, R, srInv);
return ECKey.fromPublicOnly(q.getEncoded(compressed));
}