public class RSA {/*** 定义加密方式*/private final static String KEY_RSA = "RSA";/*** 定义签名算法*/private final static String KEY_RSA_SIGNATURE = "MD5withRSA";static PrivateKey toPrivateKey(byte[] b)throws NoSuchAlgorithmException, InvalidKeySpecException {// 构造PKCS8EncodedKeySpec对象PKCS8EncodedKeySpec pkcs = new PKCS8EncodedKeySpec(b);// 指定的加密算法KeyFactory factory = KeyFactory.getInstance(KEY_RSA);// 取私钥对象return factory.generatePrivate(pkcs);}static PublicKey toPublicKey(byte[] b) throws Exception {X509EncodedKeySpec keySpec = new X509EncodedKeySpec(b);KeyFactory factory = KeyFactory.getInstance(KEY_RSA);return factory.generatePublic(keySpec);}// 用私钥对data签名public static byte[] sign(byte[] data, byte[] privateKey) throws Exception {Signature signature = Signature.getInstance(KEY_RSA_SIGNATURE);signature.initSign(toPrivateKey(privateKey));signature.update(data);return signature.sign();}// 公钥解密数据public static boolean verify(byte[] data, byte[] publicKey, byte[] sign)throws Exception {Signature signature = Signature.getInstance(KEY_RSA_SIGNATURE);signature.initVerify(toPublicKey(publicKey));signature.update(data);return signature.verify(sign);}public static byte[] decryptByPrivateKey(byte[] data, byte[] key)throws Exception {Cipher cipher = Cipher.getInstance(KEY_RSA);cipher.init(Cipher.DECRYPT_MODE, toPrivateKey(key));return cipher.doFinal(data);}public static byte[] decryptByPublicKey(byte[] data, byte[] key)throws Exception {Cipher cipher = Cipher.getInstance(KEY_RSA);cipher.init(Cipher.DECRYPT_MODE, toPublicKey(key));return cipher.doFinal(data);}public static byte[] encryptByPublicKey(byte[] data, byte[] key)throws Exception {Cipher cipher = Cipher.getInstance(KEY_RSA);cipher.init(Cipher.ENCRYPT_MODE, toPublicKey(key));return cipher.doFinal(data);}public static byte[] encryptByPrivateKey(byte[] data, byte[] key)throws Exception {Cipher cipher = Cipher.getInstance(KEY_RSA);cipher.init(Cipher.ENCRYPT_MODE, toPrivateKey(key));return cipher.doFinal(data);}static String tos(byte[] b) {String ans = "";for (int i = 0; i < b.length; i++) {ans += String.format("%02X", b[i]);}return ans;}public static void main(String[] args) throws Exception {KeyPairGenerator generator = KeyPairGenerator.getInstance(KEY_RSA);// generator.initialize(1024);//默认为1024KeyPair keyPair = generator.generateKeyPair();RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();System.out.println("公钥:" + tos(publicKey.getEncoded()));System.out.println("私钥:" + tos(privateKey.getEncoded()));byte[] data = "你好，世界！".getBytes();System.out.println("公钥加密-------私钥解密");byte[] enc = encryptByPublicKey(data, publicKey.getEncoded());byte[] dec = decryptByPrivateKey(enc, privateKey.getEncoded());System.out.println("加密前:" + tos(data));System.out.println("解密后:" + tos(dec));System.out.println("私钥加密--------公钥解密");enc = encryptByPrivateKey(data, privateKey.getEncoded());dec = decryptByPublicKey(enc, publicKey.getEncoded());System.out.println("加密前:" + tos(data));System.out.println("解密后:" + tos(dec));System.out.println("私钥签名--------公钥验证签名");byte[] sign = sign(data, privateKey.getEncoded());boolean status = verify(data, publicKey.getEncoded(), sign);System.out.println("签名:" + tos(sign));System.out.println("状态:" + status);}
}