对称加密与非对称加密实战( 三 ) _对称加密

* 公钥解密*

** @param encryptedData 已加密数据* @param publicKey 公钥(BASE64编码)* @return* @throws Exception*/public static byte[] decryptByPublicKey(byte[] encryptedData, String publicKey)throws Exception {byte[] keyBytes = decode(publicKey);X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);Key publicK = keyFactory.generatePublic(x509KeySpec);Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());cipher.init(Cipher.DECRYPT_MODE, publicK);int inputLen = encryptedData.length;ByteArrayOutputStream out = new ByteArrayOutputStream();int offSet = 0;byte[] cache;int i = 0;// 对数据分段解密while (inputLen - offSet > 0) {if (inputLen - offSet > MAX_DECRYPT_BLOCK) {cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);} else {cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);}out.write(cache, 0, cache.length);i++;offSet = i * MAX_DECRYPT_BLOCK;}byte[] decryptedData = out.toByteArray();out.close();return decryptedData;}/***

* 公钥加密*

** @param data 源数据* @param publicKey 公钥(BASE64编码)* @return* @throws Exception*/public static byte[] encryptByPublicKey(byte[] data, String publicKey)throws Exception {byte[] keyBytes = decode(publicKey);X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);Key publicK = keyFactory.generatePublic(x509KeySpec);// 对数据加密Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());cipher.init(Cipher.ENCRYPT_MODE, publicK);int inputLen = data.length;ByteArrayOutputStream out = new ByteArrayOutputStream();int offSet = 0;byte[] cache;int i = 0;// 对数据分段加密while (inputLen - offSet > 0) {if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);} else {cache = cipher.doFinal(data, offSet, inputLen - offSet);}out.write(cache, 0, cache.length);i++;offSet = i * MAX_ENCRYPT_BLOCK;}byte[] encryptedData = out.toByteArray();out.close();return encryptedData;}/***

* 私钥加密*

** @param data 源数据* @param privateKey 私钥(BASE64编码)* @return* @throws Exception*/public static byte[] encryptByPrivateKey(byte[] data, String privateKey)throws Exception {byte[] keyBytes = decode(privateKey);PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());cipher.init(Cipher.ENCRYPT_MODE, privateK);int inputLen = data.length;ByteArrayOutputStream out = new ByteArrayOutputStream();int offSet = 0;byte[] cache;int i = 0;// 对数据分段加密while (inputLen - offSet > 0) {if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);} else {cache = cipher.doFinal(data, offSet, inputLen - offSet);}out.write(cache, 0, cache.length);i++;offSet = i * MAX_ENCRYPT_BLOCK;}byte[] encryptedData = out.toByteArray();out.close();return encryptedData;}/***

* 获取私钥*

** @param keyMap 密钥对* @return* @throws Exception*/public static String getPrivateKey(Map keyMap)throws Exception {Key key = (Key) keyMap.get(PRIVATE_KEY);return encode(key.getEncoded());}/***

* 获取公钥*

** @param keyMap 密钥对* @return* @throws Exception*/public static String getPublicKey(Map keyMap)throws Exception {Key key = (Key) keyMap.get(PUBLIC_KEY);return encode(key.getEncoded());}public static byte[] decode(String base64) throws Exception {return Base64.decode(base64.getBytes());}/***

* 二进制数据编码为BASE64字符串*

** @param bytes* @return* @throws Exception*/public static String encode(byte[] bytes) throws Exception {return new String(Base64.encode(bytes));}}
【对称加密与非对称加密实战】