JDK自带方法实现RSA对称加密

  1 package jdbc.pro.lin;
  2
  3 import java.security.InvalidKeyException;
  4 import java.security.Key;
  5 import java.security.KeyFactory;
  6 import java.security.KeyPair;
  7 import java.security.KeyPairGenerator;
  8 import java.security.NoSuchAlgorithmException;
  9 import java.security.PrivateKey;
 10 import java.security.PublicKey;
 11 import java.security.interfaces.RSAPrivateKey;
 12 import java.security.interfaces.RSAPublicKey;
 13 import java.security.spec.InvalidKeySpecException;
 14 import java.security.spec.PKCS8EncodedKeySpec;
 15 import java.security.spec.X509EncodedKeySpec;
 16 import java.util.HashMap;
 17 import java.util.Map;
 18
 19 import javax.crypto.BadPaddingException;
 20 import javax.crypto.Cipher;
 21 import javax.crypto.IllegalBlockSizeException;
 22 import javax.crypto.NoSuchPaddingException;
 23
 24 import org.apache.commons.codec.binary.Base64;
 25
 26 public class MyRSA {
 27     public static final String KEY_ALGORITHM = "RSA";
 28     /** 貌似默认是RSA/NONE/PKCS1Padding，未验证 */
 29     public static final String CIPHER_ALGORITHM = "RSA/ECB/PKCS1Padding";
 30     public static final String PUBLIC_KEY = "publicKey";
 31     public static final String PRIVATE_KEY = "privateKey";
 32
 33     /** RSA密钥长度必须是64的倍数，在512~65536之间。默认是1024 */
 34     public static final int KEY_SIZE = 2048;
 35
 36     public static final String PLAIN_TEXT = "MANUTD is the greatest club in the world";
 37
 38     public static void main(String[] args) {
 39         Map<String, byte[]> keyMap = generateKeyBytes();
 40
 41         // 加密
 42         PrivateKey privateKey = restorePrivateKey(keyMap.get(PRIVATE_KEY));
 43         byte[] encodedText = RSAEncode(privateKey, PLAIN_TEXT.getBytes());
 44         System.out.println("RSA encoded: " + Base64.encodeBase64String(encodedText));
 45
 46         // 解密
 47         PublicKey publicKey = restorePublicKey(keyMap.get(PUBLIC_KEY));
 48         System.out.println("RSA decoded: "
 49                 + RSADecode(publicKey, encodedText));
 50     }
 51
 52     /**
 53      * 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
 54      *
 55      * @return
 56      */
 57     public static Map<String, byte[]> generateKeyBytes() {
 58
 59         try {
 60             KeyPairGenerator keyPairGenerator = KeyPairGenerator
 61                     .getInstance(KEY_ALGORITHM);
 62             keyPairGenerator.initialize(KEY_SIZE);
 63             KeyPair keyPair = keyPairGenerator.generateKeyPair();
 64             RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
 65             RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
 66
 67             Map<String, byte[]> keyMap = new HashMap<String, byte[]>();
 68             keyMap.put(PUBLIC_KEY, publicKey.getEncoded());
 69             keyMap.put(PRIVATE_KEY, privateKey.getEncoded());
 70             return keyMap;
 71         } catch (NoSuchAlgorithmException e) {
 72             // TODO Auto-generated catch block
 73             e.printStackTrace();
 74         }
 75         return null;
 76     }
 77
 78     /**
 79      * 还原公钥，X509EncodedKeySpec 用于构建公钥的规范
 80      *
 81      * @param keyBytes
 82      * @return
 83      */
 84     public static PublicKey restorePublicKey(byte[] keyBytes) {
 85         X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(keyBytes);
 86
 87         try {
 88             KeyFactory factory = KeyFactory.getInstance(KEY_ALGORITHM);
 89             PublicKey publicKey = factory.generatePublic(x509EncodedKeySpec);
 90             return publicKey;
 91         } catch (NoSuchAlgorithmException | InvalidKeySpecException e) {
 92             // TODO Auto-generated catch block
 93             e.printStackTrace();
 94         }
 95         return null;
 96     }
 97
 98     /**
 99      * 还原私钥，PKCS8EncodedKeySpec 用于构建私钥的规范
100      *
101      * @param keyBytes
102      * @return
103      */
104     public static PrivateKey restorePrivateKey(byte[] keyBytes) {
105         PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(
106                 keyBytes);
107         try {
108             KeyFactory factory = KeyFactory.getInstance(KEY_ALGORITHM);
109             PrivateKey privateKey = factory
110                     .generatePrivate(pkcs8EncodedKeySpec);
111             return privateKey;
112         } catch (NoSuchAlgorithmException | InvalidKeySpecException e) {
113             // TODO Auto-generated catch block
114             e.printStackTrace();
115         }
116         return null;
117     }
118
119     /**
120      * 加密，三步走。
121      *
122      * @param key
123      * @param plainText
124      * @return
125      */
126     public static byte[] RSAEncode(PrivateKey key, byte[] plainText) {
127
128         try {
129             Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);
130             cipher.init(Cipher.ENCRYPT_MODE, key);
131             return cipher.doFinal(plainText);
132         } catch (NoSuchAlgorithmException | NoSuchPaddingException
133                 | InvalidKeyException | IllegalBlockSizeException
134                 | BadPaddingException e) {
135             // TODO Auto-generated catch block
136             e.printStackTrace();
137         }
138         return null;
139
140     }
141
142     /**
143      * 解密，三步走。
144      *
145      * @param key
146      * @param encodedText
147      * @return
148      */
149     public static String RSADecode(PublicKey key, byte[] encodedText) {
150
151         try {
152             Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);
153             cipher.init(Cipher.DECRYPT_MODE, key);
154             return new String(cipher.doFinal(encodedText));
155         } catch (NoSuchAlgorithmException | NoSuchPaddingException
156                 | InvalidKeyException | IllegalBlockSizeException
157                 | BadPaddingException e) {
158             // TODO Auto-generated catch block
159             e.printStackTrace();
160         }
161         return null;
162
163     }
164 }

几点注意：

1.用到了KeyFactory。

2.用到了公私钥的规范。

3.RSA密钥长度从512~65536，必须是64的整数倍