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 [J2SE]java非对称加密的源代码(RSA)
软件技术, 电脑与网络
lhwork 发表于 2006/6/27 15:40:18 |
| 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。 |
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