利用Java6和BouncyCastle对文件进行加解密

Bouncy Castle提供的下载地址（http://www.bouncycastle.org/latest_releases.html），下载最新的加密组件包，主要是bcprov-jdk16-143.jar和bcprov-ext-jdk16-143.jar两个文件，当然这里只用bcprov-jdk16-143.jar，自己可以去下载添加到项目中。

 

package sample; 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。 非对称加密， 2011年1月18日 16:45:28 漆艾林 */ public class RSAUtil { /** * 生成密钥对 * * @return KeyPair * @throws EncryptException */ public static KeyPair generateKeyPair() throws Exception { 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 Exception(e.getMessage()); } } /** * 生成公钥 * * @param modulus * @param publicEXPonent * @return RSAPublicKey * @throws EncryptException */ public static RSAPublicKey generateRSAPublicKey(byte[] modulus, byte[] publicExponent) throws Exception { KeyFactory keyFac = null; keyFac = KeyFactory.getInstance("RSA", new org.bouncycastle.jce.provider.BouncyCastleProvider()); RSAPublicKeySpec pubKeySpec = new RSAPublicKeySpec(new BigInteger(modulus), new BigInteger( publicExponent)); try { return (RSAPublicKey) keyFac.generatePublic(pubKeySpec); } catch (InvalidKeySpecException ex) { throw new Exception(ex.getMessage()); } } /** * 生成私钥 * * @param modulus * @param privateExponent * @return RSAPrivateKey * @throws EncryptException */ 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()); } } /** * 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 Exception { 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 Exception(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 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()); } } /** * 这里我是对相对路径的文件进行加解密 路径可以自己修改src/test.txt 相对路径前面不要带/ QQ172794299 * * @param args * @throws Exception */ public static void main(String[] args) throws Exception { File file = new File("src/test.txt"); 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(recoveryPriKey, orgData); file = new File("encryptresult.txt"); OutputStream out = new FileOutputStream(file); out.write(raw); out.close(); byte[] data = RSAUtil.decrypt(recoveryPubKey, raw); file = new File("decryptresult.txt"); out = new FileOutputStream(file); out.write(data); out.flush(); out.close(); } }