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org.bouncycastle.crypto.engines.SM2Engine Maven / Gradle / Ivy
package org.bouncycastle.crypto.engines;
import java.math.BigInteger;
import java.security.SecureRandom;
import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.Digest;
import org.bouncycastle.crypto.InvalidCipherTextException;
import org.bouncycastle.crypto.digests.SM3Digest;
import org.bouncycastle.crypto.params.ECDomainParameters;
import org.bouncycastle.crypto.params.ECKeyParameters;
import org.bouncycastle.crypto.params.ECPrivateKeyParameters;
import org.bouncycastle.crypto.params.ECPublicKeyParameters;
import org.bouncycastle.crypto.params.ParametersWithRandom;
import org.bouncycastle.math.ec.ECFieldElement;
import org.bouncycastle.math.ec.ECMultiplier;
import org.bouncycastle.math.ec.ECPoint;
import org.bouncycastle.math.ec.FixedPointCombMultiplier;
import org.bouncycastle.util.Arrays;
import org.bouncycastle.util.BigIntegers;
import org.bouncycastle.util.Memoable;
import org.bouncycastle.util.Pack;
/**
* SM2 public key encryption engine - based on https://tools.ietf.org/html/draft-shen-sm2-ecdsa-02.
*/
public class SM2Engine
{
public enum Mode
{
C1C2C3, C1C3C2;
}
private final Digest digest;
private final Mode mode;
private boolean forEncryption;
private ECKeyParameters ecKey;
private ECDomainParameters ecParams;
private int curveLength;
private SecureRandom random;
public SM2Engine()
{
this(new SM3Digest());
}
public SM2Engine(Mode mode)
{
this(new SM3Digest(), mode);
}
public SM2Engine(Digest digest)
{
this(digest, Mode.C1C2C3);
}
public SM2Engine(Digest digest, Mode mode)
{
if (mode == null)
{
throw new IllegalArgumentException("mode cannot be NULL");
}
this.digest = digest;
this.mode = mode;
}
public void init(boolean forEncryption, CipherParameters param)
{
this.forEncryption = forEncryption;
if (forEncryption)
{
ParametersWithRandom rParam = (ParametersWithRandom)param;
ecKey = (ECKeyParameters)rParam.getParameters();
ecParams = ecKey.getParameters();
ECPoint s = ((ECPublicKeyParameters)ecKey).getQ().multiply(ecParams.getH());
if (s.isInfinity())
{
throw new IllegalArgumentException("invalid key: [h]Q at infinity");
}
random = rParam.getRandom();
}
else
{
ecKey = (ECKeyParameters)param;
ecParams = ecKey.getParameters();
}
curveLength = (ecParams.getCurve().getFieldSize() + 7) / 8;
}
public byte[] processBlock(
byte[] in,
int inOff,
int inLen)
throws InvalidCipherTextException
{
if (forEncryption)
{
return encrypt(in, inOff, inLen);
}
else
{
return decrypt(in, inOff, inLen);
}
}
public int getOutputSize(int inputLen)
{
return (1 + 2 * curveLength) + inputLen + digest.getDigestSize();
}
protected ECMultiplier createBasePointMultiplier()
{
return new FixedPointCombMultiplier();
}
private byte[] encrypt(byte[] in, int inOff, int inLen)
throws InvalidCipherTextException
{
byte[] c2 = new byte[inLen];
System.arraycopy(in, inOff, c2, 0, c2.length);
ECMultiplier multiplier = createBasePointMultiplier();
byte[] c1;
ECPoint kPB;
do
{
BigInteger k = nextK();
ECPoint c1P = multiplier.multiply(ecParams.getG(), k).normalize();
c1 = c1P.getEncoded(false);
kPB = ((ECPublicKeyParameters)ecKey).getQ().multiply(k).normalize();
kdf(digest, kPB, c2);
}
while (notEncrypted(c2, in, inOff));
byte[] c3 = new byte[digest.getDigestSize()];
addFieldElement(digest, kPB.getAffineXCoord());
digest.update(in, inOff, inLen);
addFieldElement(digest, kPB.getAffineYCoord());
digest.doFinal(c3, 0);
switch (mode)
{
case C1C3C2:
return Arrays.concatenate(c1, c3, c2);
default:
return Arrays.concatenate(c1, c2, c3);
}
}
private byte[] decrypt(byte[] in, int inOff, int inLen)
throws InvalidCipherTextException
{
byte[] c1 = new byte[curveLength * 2 + 1];
System.arraycopy(in, inOff, c1, 0, c1.length);
ECPoint c1P = ecParams.getCurve().decodePoint(c1);
ECPoint s = c1P.multiply(ecParams.getH());
if (s.isInfinity())
{
throw new InvalidCipherTextException("[h]C1 at infinity");
}
c1P = c1P.multiply(((ECPrivateKeyParameters)ecKey).getD()).normalize();
int digestSize = this.digest.getDigestSize();
byte[] c2 = new byte[inLen - c1.length - digestSize];
if (mode == Mode.C1C3C2)
{
System.arraycopy(in, inOff + c1.length + digestSize, c2, 0, c2.length);
}
else
{
System.arraycopy(in, inOff + c1.length, c2, 0, c2.length);
}
kdf(digest, c1P, c2);
byte[] c3 = new byte[digest.getDigestSize()];
addFieldElement(digest, c1P.getAffineXCoord());
digest.update(c2, 0, c2.length);
addFieldElement(digest, c1P.getAffineYCoord());
digest.doFinal(c3, 0);
int check = 0;
if (mode == Mode.C1C3C2)
{
for (int i = 0; i != c3.length; i++)
{
check |= c3[i] ^ in[inOff + c1.length + i];
}
}
else
{
for (int i = 0; i != c3.length; i++)
{
check |= c3[i] ^ in[inOff + c1.length + c2.length + i];
}
}
Arrays.fill(c1, (byte)0);
Arrays.fill(c3, (byte)0);
if (check != 0)
{
Arrays.fill(c2, (byte)0);
throw new InvalidCipherTextException("invalid cipher text");
}
return c2;
}
private boolean notEncrypted(byte[] encData, byte[] in, int inOff)
{
for (int i = 0; i != encData.length; i++)
{
if (encData[i] != in[inOff + i])
{
return false;
}
}
return true;
}
private void kdf(Digest digest, ECPoint c1, byte[] encData)
{
int digestSize = digest.getDigestSize();
byte[] buf = new byte[Math.max(4, digestSize)];
int off = 0;
Memoable memo = null;
Memoable copy = null;
if (digest instanceof Memoable)
{
addFieldElement(digest, c1.getAffineXCoord());
addFieldElement(digest, c1.getAffineYCoord());
memo = (Memoable)digest;
copy = memo.copy();
}
int ct = 0;
while (off < encData.length)
{
if (memo != null)
{
memo.reset(copy);
}
else
{
addFieldElement(digest, c1.getAffineXCoord());
addFieldElement(digest, c1.getAffineYCoord());
}
Pack.intToBigEndian(++ct, buf, 0);
digest.update(buf, 0, 4);
digest.doFinal(buf, 0);
int xorLen = Math.min(digestSize, encData.length - off);
xor(encData, buf, off, xorLen);
off += xorLen;
}
}
private void xor(byte[] data, byte[] kdfOut, int dOff, int dRemaining)
{
for (int i = 0; i != dRemaining; i++)
{
data[dOff + i] ^= kdfOut[i];
}
}
private BigInteger nextK()
{
int qBitLength = ecParams.getN().bitLength();
BigInteger k;
do
{
k = BigIntegers.createRandomBigInteger(qBitLength, random);
}
while (k.equals(BigIntegers.ZERO) || k.compareTo(ecParams.getN()) >= 0);
return k;
}
private void addFieldElement(Digest digest, ECFieldElement v)
{
byte[] p = BigIntegers.asUnsignedByteArray(curveLength, v.toBigInteger());
digest.update(p, 0, p.length);
}
}
