RSA对文件进行加密和解密

package author.estone.rsa;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。 *  */public class RSAUtil {/** * 生成密钥对 *  * @return KeyPair * @throws */public static KeyPair generateKeyPair() {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) {return null;}}/** * 生成公钥 *  * @param modulus * @param publicExponent * @return RSAPublicKey * @throws */public static RSAPublicKey generateRSAPublicKey(byte[] modulus,byte[] publicExponent) {KeyFactory keyFac = null;try {keyFac = KeyFactory.getInstance("RSA",new org.bouncycastle.jce.provider.BouncyCastleProvider());} catch (NoSuchAlgorithmException ex) {}RSAPublicKeySpec pubKeySpec = new RSAPublicKeySpec(new BigInteger(modulus), new BigInteger(publicExponent));try {return (RSAPublicKey) keyFac.generatePublic(pubKeySpec);} catch (InvalidKeySpecException ex) {return null;}}/** * 生成私钥 *  * @param modulus * @param privateExponent * @return RSAPrivateKey * @throws */public static RSAPrivateKey generateRSAPrivateKey(byte[] modulus,byte[] privateExponent) {KeyFactory keyFac = null;try {keyFac = KeyFactory.getInstance("RSA",new org.bouncycastle.jce.provider.BouncyCastleProvider());} catch (NoSuchAlgorithmException ex) {}RSAPrivateKeySpec priKeySpec = new RSAPrivateKeySpec(new BigInteger(modulus), new BigInteger(privateExponent));try {return (RSAPrivateKey) keyFac.generatePrivate(priKeySpec);} catch (InvalidKeySpecException ex) {return null;}}/** * 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 */public static byte[] encrypt(Key key, byte[] data) {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byteint 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);elsecipher.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) {return null;}}/** * 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 */public static byte[] decrypt(Key key, byte[] raw) {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) {return null;}}/** *  * @param args * @throws Exception */public static void main(String[] args) throws Exception {// 读取要加密的文件File file = new File("d:/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();// 对数据文件进行加密处理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);// 对文件进行加密byte[] raw = RSAUtil.encrypt(priKey, orgData);file = new File("encrypt_result.dat");OutputStream out = new FileOutputStream(file);out.write(raw);out.close();// 对文件进行解密byte[] data = RSAUtil.decrypt(recoveryPubKey, raw);file = new File("decrypt_result.html");out = new FileOutputStream(file);out.write(data);out.flush();out.close();}}

?code from :

http://code.google.com/p/jsc4/source/browse/trunk/JSC4/src/eticketApplet/RSAUtil.java?spec=svn35&r=35