Cipher.java

package com.lzk.gdut.sm;

import java.math.BigInteger;

import org.bouncycastle.crypto.AsymmetricCipherKeyPair;
import org.bouncycastle.crypto.params.ECPrivateKeyParameters;
import org.bouncycastle.crypto.params.ECPublicKeyParameters;
import org.bouncycastle.math.ec.ECPoint;

public class Cipher 
{
	private int ct;
	private ECPoint p2;
	private SM3Digest sm3keybase;
	private SM3Digest sm3c3;
	private byte key[];
	private byte keyOff;

	public Cipher() 
	{
		this.ct = 1;
		this.key = new byte[32];
		this.keyOff = 0;
	}

	private void Reset() 
	{
		this.sm3keybase = new SM3Digest();
		this.sm3c3 = new SM3Digest();
		
		byte p[] = Util.byteConvert32Bytes(p2.getX().toBigInteger());
		this.sm3keybase.update(p, 0, p.length);
		this.sm3c3.update(p, 0, p.length);
		
		p = Util.byteConvert32Bytes(p2.getY().toBigInteger());
		this.sm3keybase.update(p, 0, p.length);
		this.ct = 1;
		NextKey();
	}

	private void NextKey() 
	{
		SM3Digest sm3keycur = new SM3Digest(this.sm3keybase);
		sm3keycur.update((byte) (ct >> 24 & 0xff));
		sm3keycur.update((byte) (ct >> 16 & 0xff));
		sm3keycur.update((byte) (ct >> 8 & 0xff));
		sm3keycur.update((byte) (ct & 0xff));
		sm3keycur.doFinal(key, 0);
		this.keyOff = 0;
		this.ct++;
	}

	public ECPoint Init_enc(SM2 sm2, ECPoint userKey) 
	{
		AsymmetricCipherKeyPair key = sm2.ecc_key_pair_generator.generateKeyPair();
		ECPrivateKeyParameters ecpriv = (ECPrivateKeyParameters) key.getPrivate();
		ECPublicKeyParameters ecpub = (ECPublicKeyParameters) key.getPublic();
		BigInteger k = ecpriv.getD();
		ECPoint c1 = ecpub.getQ();
		this.p2 = userKey.multiply(k);
		Reset();
		return c1;
	}

	public void Encrypt(byte data[]) 
	{
		this.sm3c3.update(data, 0, data.length);
		for (int i = 0; i < data.length; i++) 
		{
			if (keyOff == key.length)
			{
				NextKey();
			}
			data[i] ^= key[keyOff++];
		}
	}

	public void Init_dec(BigInteger userD, ECPoint c1)
	{
		this.p2 = c1.multiply(userD);
		Reset();
	}

	public void Decrypt(byte data[]) 
	{
		for (int i = 0; i < data.length; i++)
		{
			if (keyOff == key.length)
			{
				NextKey();
			}
			data[i] ^= key[keyOff++];
		}

		this.sm3c3.update(data, 0, data.length);
	}

	public void Dofinal(byte c3[]) 
	{
		byte p[] = Util.byteConvert32Bytes(p2.getY().toBigInteger());
		this.sm3c3.update(p, 0, p.length);
		this.sm3c3.doFinal(c3, 0);
		Reset();
	}
}