java非对称加密的源代码(RSA)

1/5/2008来源:Java教程人气:6594


  鉴于rsa加密的重要性和相关源代码的匮乏,经过整理特此贴出。需要下载bcPRov-jdk14-123.jar。
  
  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;
  
  /**
  * RSA 工具类。提供加密,解密,生成密钥对等方法。
  * 需要到http://www.bouncycastle.org下载bcprov-jdk14-123.jar。
  *
  */
  public class RSAUtil {
  
  /**
  * 生成密钥对
  * @return KeyPair
  * @throws EncryptException
  */
  public static KeyPair generateKeyPair() throws EncryptException {
  try {
  KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA",
  new org.bouncycastle.jce.provider.BouncyCastleProvider());
  final int KEY_SIZE = 1024;//没什么好说的了,这个值关系到块加密的大小,可以更改,但是不要太大,否则效率会低
  keyPairGen.initialize(KEY_SIZE, new SecureRandom());
  KeyPair keyPair = keyPairGen.genKeyPair();
  return keyPair;
  } catch (Exception e) {
  throw new EncryptException(e.getMessage());
  }
  }
  /**
  * 生成公钥
  * @param modulus
  * @param publicEXPonent
  * @return RSAPublicKey
  * @throws EncryptException
  */
  public static RSAPublicKey generateRSAPublicKey(byte[] modulus, byte[] publicExponent) throws EncryptException {
  KeyFactory keyFac = null;
  try {
  keyFac = KeyFactory.getInstance("RSA", new org.bouncycastle.jce.provider.BouncyCastleProvider());
  } catch (NoSUChAlgorithmException ex) {
  throw new EncryptException(ex.getMessage());
  }
  
  RSAPublicKeySpec pubKeySpec = new RSAPublicKeySpec(new BigInteger(modulus), new BigInteger(publicExponent));
  try {
  return (RSAPublicKey) keyFac.generatePublic(pubKeySpec);
  } catch (InvalidKeySpecException ex) {
  throw new EncryptException(ex.getMessage());
  }
  }
  /**
  * 生成私钥
  * @param modulus
  * @param privateExponent
  * @return RSAPrivateKey
  * @throws EncryptException
  */
  public static RSAPrivateKey generateRSAPrivateKey(byte[] modulus, byte[] privateExponent) throws EncryptException {
  KeyFactory keyFac = null;
  try {
  keyFac = KeyFactory.getInstance("RSA", new org.bouncycastle.jce.provider.BouncyCastleProvider());
  } catch (NoSuchAlgorithmException ex) {
  throw new EncryptException(ex.getMessage());
  }
  
  RSAPrivateKeySpec priKeySpec = new RSAPrivateKeySpec(new BigInteger(modulus), new BigInteger(privateExponent));
  try {
  return (RSAPrivateKey) keyFac.generatePrivate(priKeySpec);
  } catch (InvalidKeySpecException ex) {
  throw new EncryptException(ex.getMessage());
  }
  }
  /**
  * 加密
  * @param key 加密的密钥
  * @param data 待加密的明文数据
  * @return 加密后的数据
  * @throws EncryptException
  */
  public static byte[] encrypt(Key key, byte[] data) throws EncryptException {
  try {
  Cipher cipher = Cipher.getInstance("RSA", new org.bouncycastle.jce.provider.BouncyCastleProvider());
  cipher.init(Cipher.ENCRYPT_MODE, key);
  int blockSize = cipher.getBlockSize();//获得加密块大小,如:加密前数据为128个byte,而key_size=1024 加密块大小为127 byte,加密后为128个byte;因此共有2个加密块,第一个127 byte第二个为1个byte
  int outputSize = cipher.getOutputSize(data.length);//获得加密块加密后块大小
  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);
  //这里面doUpdate方法不可用,查看源代码后发现每次doUpdate后并没有什么实际动作除了把byte[]放到ByteArrayOutputStream中,而最后doFinal的时候才将所有的byte[]进行加密,可是到了此时加密块大小很可能已经超出了OutputSize所以只好用dofinal方法。
  
  i++;
  }
  return raw;
  } catch (Exception e) {
  throw new EncryptException(e.getMessage());
  }
  }
  /**
  * 解密
  * @param key 解密的密钥
  * @param raw 已经加密的数据
  * @return 解密后的明文
  * @throws EncryptException
  */
  public static byte[] decrypt(Key key, byte[] raw) throws EncryptException {
  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 EncryptException(e.getMessage());
  }
  }
  /**
  *
  * @param args
  * @throws Exception
  */
  public static void main(String[] args) throws Exception {
  File file = new File("test.Html");
  FileInputStream in = new FileInputStream(file);
  ByteArrayOutputStream bout = new ByteArrayOutputStream();
  byte[] tmpbuf = new byte[1024];
  int count = 0;
  while ((count = in.read(tmpbuf)) != -1) {
  bout.write(tmpbuf, 0, count);
  tmpbuf = new byte[1024];
  }
  in.close();
  byte[] orgData = bout.toByteArray();
  KeyPair keyPair = RSAUtil.generateKeyPair();
  RSAPublicKey pubKey = (RSAPublicKey) keyPair.getPublic();
  RSAPrivateKey priKey = (RSAPrivateKey) keyPair.getPrivate();
  
  byte[] pubModBytes = pubKey.getModulus().toByteArray();
  byte[] pubPubExpBytes = pubKey.getPublicExponent().toByteArray();
  byte[] priModBytes = priKey.getModulus().toByteArray();
  byte[] priPriExpBytes = priKey.getPrivateExponent().toByteArray();
  RSAPublicKey recoveryPubKey = RSAUtil.generateRSAPublicKey(pubModBytes,pubPubExpBytes);
  RSAPrivateKey recoveryPriKey = RSAUtil.generateRSAPrivateKey(priModBytes,priPriExpBytes);
  
  byte[] raw = RSAUtil.encrypt(priKey, orgData);
  file = new File("encrypt_result.dat");
  OutputStream out = new FileOutputStream(file);
  out.write(raw);
  out.close();
  byte[] data = RSAUtil.decrypt(recoveryPubKey, raw);
  file = new File("decrypt_result.html");
  out = new FileOutputStream(file);
  out.write(data);
  out.flush();
  out.close();
  }
  }
  
  加密可以用公钥,解密用私钥;或者加密用私钥。通常非对称加密是非常消耗资源的,因此可以对大数据用对称加密如:des(具体代码可以看我以前发的贴子),而对其对称密钥进行非对称加密,这样既保证了数据的安全,还能保证效率。