rsautil.java

MD5加密算法

package t26lab3_2.GUI;
import javax.crypto.Cipher;
import java.security.*;
import java.security.spec.RSAPublicKeySpec;
import java.security.spec.RSAPrivateKeySpec;
import java.security.spec.InvalidKeySpecException;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.io.*;
import java.math.BigInteger;

public class RSAUtil {
   
    public static KeyPair generateKeyPair() throws Exception {
        try {
            KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA",
                    new org.bouncycastle.jce.provider.BouncyCastleProvider());
            final int KEY_SIZE = 1024;
            keyPairGen.initialize(KEY_SIZE, new SecureRandom());
            KeyPair keyPair = keyPairGen.genKeyPair();
            return keyPair;
        } catch (Exception e) {
            throw new Exception(e.getMessage());
        }
    }

    public static RSAPublicKey generateRSAPublicKey(byte[] modulus, byte[] publicExponent) throws Exception {
        KeyFactory keyFac = null;
        try {
            keyFac = KeyFactory.getInstance("RSA", new org.bouncycastle.jce.provider.BouncyCastleProvider());
        } catch (NoSuchAlgorithmException ex) {
            throw new Exception(ex.getMessage());
        }

        RSAPublicKeySpec pubKeySpec = new RSAPublicKeySpec(new BigInteger(modulus), new BigInteger(publicExponent));
        try {
            return (RSAPublicKey) keyFac.generatePublic(pubKeySpec);
        } catch (InvalidKeySpecException ex) {
            throw new Exception(ex.getMessage());
        }
    }

    public static RSAPrivateKey generateRSAPrivateKey(byte[] modulus, byte[] privateExponent) throws Exception {
        KeyFactory keyFac = null;
        try {
            keyFac = KeyFactory.getInstance("RSA", new org.bouncycastle.jce.provider.BouncyCastleProvider());
        } catch (NoSuchAlgorithmException ex) {
            throw new Exception(ex.getMessage());
        }

        RSAPrivateKeySpec priKeySpec = new RSAPrivateKeySpec(new BigInteger(modulus), new BigInteger(privateExponent));
        try {
            return (RSAPrivateKey) keyFac.generatePrivate(priKeySpec);
        } catch (InvalidKeySpecException ex) {
            throw new Exception(ex.getMessage());
        }
    }

    public static byte[] encrypt(Key key, byte[] data) throws Exception {
        try {
            Cipher cipher = Cipher.getInstance("RSA", new org.bouncycastle.jce.provider.BouncyCastleProvider());
            cipher.init(Cipher.ENCRYPT_MODE, key);            

            int blockSize = cipher.getBlockSize();
            
            int outputSize = cipher.getOutputSize(data.length);
            int leavedSize = data.length % blockSize;
            int blocksSize = leavedSize != 0 ? data.length / blockSize + 1 : data.length / blockSize;
            byte[] raw = new byte[outputSize * blocksSize];
            int i = 0;
            while (data.length - i * blockSize > 0) {
                if (data.length - i * blockSize > blockSize)
                    cipher.doFinal(data, i * blockSize, blockSize, raw, i * outputSize);
                else
                    cipher.doFinal(data, i * blockSize, data.length - i * blockSize, raw, i * outputSize);
                i++;
            }
            return raw;
        } catch (Exception e) {
            throw new Exception(e.getMessage());
        }
    }    
    
    
    public static byte[] decrypt(Key key, byte[] raw) throws Exception {
        try {
            Cipher cipher = Cipher.getInstance("RSA", new org.bouncycastle.jce.provider.BouncyCastleProvider());
            cipher.init(Cipher.DECRYPT_MODE, key);
            int blockSize = cipher.getBlockSize();
            ByteArrayOutputStream bout = new ByteArrayOutputStream(64);
            int j = 0;
            while (raw.length - j * blockSize > 0) {
                bout.write(cipher.doFinal(raw, j * blockSize, blockSize));
                j++;
            }
            return bout.toByteArray();
        } catch (Exception e) {
            throw new Exception(e.getMessage());
        }
    }   
}