JDK自带方法实现RSA非对称加密

package jdbc.pro.lin;

import java.security.InvalidKeyException;
import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;

import org.apache.commons.codec.binary.Base64;

public class MyRSA {
public static final String KEY_ALGORITHM = "RSA";
/** 貌似默认是RSA/NONE/PKCS1Padding，未验证 */
public static final String CIPHER_ALGORITHM = "RSA/ECB/PKCS1Padding";
public static final String PUBLIC_KEY = "publicKey";
public static final String PRIVATE_KEY = "privateKey";

/** RSA密钥长度必须是64的倍数，在512~65536之间。默认是1024 */
public static final int KEY_SIZE = 2048;

public static final String PLAIN_TEXT = "MANUTD is the greatest club in the world";

public static void main(String[] args) {
Map<String, byte[]> keyMap = generateKeyBytes();

// 加密
PublicKey publicKey = restorePublicKey(keyMap.get(PUBLIC_KEY));

byte[] encodedText = RSAEncode(publicKey, PLAIN_TEXT.getBytes());
System.out.println("RSA encoded: " + Base64.encodeBase64String(encodedText));

// 解密
PrivateKey privateKey = restorePrivateKey(keyMap.get(PRIVATE_KEY));
System.out.println("RSA decoded: "
+ RSADecode(privateKey, encodedText));
}

/**
* 生成密钥对。注意这里是生成密钥对KeyPair，再由密钥对获取公私钥
*
* @return
*/
public static Map<String, byte[]> generateKeyBytes() {

try {
KeyPairGenerator keyPairGenerator = KeyPairGenerator
.getInstance(KEY_ALGORITHM);
keyPairGenerator.initialize(KEY_SIZE);
KeyPair keyPair = keyPairGenerator.generateKeyPair();
RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();

Map<String, byte[]> keyMap = new HashMap<String, byte[]>();
keyMap.put(PUBLIC_KEY, publicKey.getEncoded());
keyMap.put(PRIVATE_KEY, privateKey.getEncoded());
return keyMap;
} catch (NoSuchAlgorithmException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}

/**
* 还原公钥，X509EncodedKeySpec 用于构建公钥的规范
*
* @param keyBytes
* @return
*/
public static PublicKey restorePublicKey(byte[] keyBytes) {
X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(keyBytes);

try {
KeyFactory factory = KeyFactory.getInstance(KEY_ALGORITHM);
PublicKey publicKey = factory.generatePublic(x509EncodedKeySpec);
return publicKey;
} catch (NoSuchAlgorithmException | InvalidKeySpecException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}

/**
* 还原私钥，PKCS8EncodedKeySpec 用于构建私钥的规范
*
* @param keyBytes
* @return
*/
public static PrivateKey restorePrivateKey(byte[] keyBytes) {
PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(
keyBytes);
try {
KeyFactory factory = KeyFactory.getInstance(KEY_ALGORITHM);
PrivateKey privateKey = factory
.generatePrivate(pkcs8EncodedKeySpec);
return privateKey;
} catch (NoSuchAlgorithmException | InvalidKeySpecException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}

/**
* 加密，三步走。
*
* @param key
* @param plainText
* @return
*/
public static byte[] RSAEncode(PublicKey key, byte[] plainText) {

try {
Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);
cipher.init(Cipher.ENCRYPT_MODE, key);
return cipher.doFinal(plainText);
} catch (NoSuchAlgorithmException | NoSuchPaddingException
| InvalidKeyException | IllegalBlockSizeException
| BadPaddingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;

}

/**
* 解密，三步走。
*
* @param key
* @param encodedText
* @return
*/
public static String RSADecode(PrivateKey key, byte[] encodedText) {

try {
Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);
cipher.init(Cipher.DECRYPT_MODE, key);
return new String(cipher.doFinal(encodedText));
} catch (NoSuchAlgorithmException | NoSuchPaddingException
| InvalidKeyException | IllegalBlockSizeException
| BadPaddingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;

}
}