非对称加密至RSA
JDK6.0提供了RSA加密算法的实现
在RSA算法中，公钥既可以用于解密，也可以用于加密，私钥也是如此。但是公钥加密只能私钥解密，反正私钥加密只能公钥解密。
对于JDK与 Bouncy Castle的实现如下
package test;
import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;
import javax.crypto.Cipher;
public abstract class RSACoder {
/**
* 非对称加密密钥算法
*/
public static final String KEY_ALGORITHM = "RSA";
/**
* 公钥
*/
private static final String PUBLIC_KEY = "RSAPublicKey";
/**
* 私钥
*/
private static final String PRIVATE_KEY = "RSAPrivateKey";
/**
* RSA密钥长度
* 默认1024位，
* 密钥长度必须是64的倍数，
* 范围在512至65536位之间。
*/
private static final int KEY_SIZE = 512;
/**
* 私钥解密
*
* @param data
*
待解密数据
* @param key
*
私钥
* @return byte[] 解密数据
* @throws Exception
*/
public static byte[] decryptByPrivateKey(byte[] data, byte[] key)
throws Exception {
// 取得私钥
PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(key);
KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
// 生成私钥
PrivateKey privateKey = keyFactory.generatePrivate(pkcs8KeySpec);
// 对数据解密
Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
cipher.init(Cipher.DECRYPT_MODE, privateKey);
return cipher.doFinal(data);
}
/**
* 公钥解密
*
* @param data
*
待解密数据
* @param key
*
公钥
* @return byte[] 解密数据
* @throws Exception
*/
public static byte[] decryptByPublicKey(byte[] data, byte[] key)
throws Exception {
// 取得公钥
X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(key);
KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
// 生成公钥
PublicKey publicKey = keyFactory.generatePublic(x509KeySpec);
// 对数据解密
Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
cipher.init(Cipher.DECRYPT_MODE, publicKey);
return cipher.doFinal(data);
}
/**
* 公钥加密
*
* @param data
*
待加密数据
* @param key
*
公钥
* @return byte[] 加密数据
* @throws Exception
*/
public static byte[] encryptByPublicKey(byte[] data, byte[] key)
throws Exception {
// 取得公钥
X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(key);
KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
PublicKey publicKey = keyFactory.generatePublic(x509KeySpec);
// 对数据加密
Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
cipher.init(Cipher.ENCRYPT_MODE, publicKey);
return cipher.doFinal(data);
}
/**
* 私钥加密
*
* @param data
*
待加密数据
* @param key
*
私钥
* @return byte[] 加密数据
* @throws Exception
*/
public static byte[] encryptByPrivateKey(byte[] data, byte[] key)
throws Exception {
// 取得私钥
PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(key);
KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
// 生成私钥
PrivateKey privateKey = keyFactory.generatePrivate(pkcs8KeySpec);
// 对数据加密
Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
cipher.init(Cipher.ENCRYPT_MODE, privateKey);
return cipher.doFinal(data);
}
/**
* 取得私钥
*
* @param keyMap
*
密钥Map
* @return byte[] 私钥
* @throws Exception
*/
public static byte[] getPrivateKey(Map<String, Object> keyMap)
throws Exception {
Key key = (Key) keyMap.get(PRIVATE_KEY);
return key.getEncoded();
}
/**
* 取得公钥
*
* @param keyMap
*
密钥Map
* @return byte[] 公钥
* @throws Exception
*/
public static byte[] getPublicKey(Map<String, Object> keyMap)
throws Exception {
Key key = (Key) keyMap.get(PUBLIC_KEY);
return key.getEncoded();
}
/**
* 初始化密钥
*
* @return Map 密钥Map
* @throws Exception
*/
public static Map<String, Object> initKey() throws Exception {
// 实例化密钥对生成器
KeyPairGenerator keyPairGen = KeyPairGenerator
.getInstance(KEY_ALGORITHM);
// 初始化密钥对生成器
keyPairGen.initialize(KEY_SIZE);
// 生成密钥对
KeyPair keyPair = keyPairGen.generateKeyPair();
// 公钥
RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
// 私钥
RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
// 封装密钥
Map<String, Object> keyMap = new HashMap<String, Object>(2);
keyMap.put(PUBLIC_KEY, publicKey);
keyMap.put(PRIVATE_KEY, privateKey);
return keyMap;
}
}
https://www.zhihu.com/question/35137387
