JDK自带方法实现RSA非对称加密

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         PublicKey publicKey = restorePublicKey(keyMap.get(PUBLIC_KEY)); 43          44         byte[] encodedText = RSAEncode(publicKey, PLAIN_TEXT.getBytes()); 45         System.out.println("RSA encoded: " + Base64.encodeBase64String(encodedText)); 46  47         // 解密 48         PrivateKey privateKey = restorePrivateKey(keyMap.get(PRIVATE_KEY)); 49         System.out.println("RSA decoded: " 50                 + RSADecode(privateKey, encodedText)); 51     } 52  53     /** 54      * 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 55      *  56      * @return 57      */ 58     public static Map<String, byte[]> generateKeyBytes() { 59  60         try { 61             KeyPairGenerator keyPairGenerator = KeyPairGenerator 62                     .getInstance(KEY_ALGORITHM); 63             keyPairGenerator.initialize(KEY_SIZE); 64             KeyPair keyPair = keyPairGenerator.generateKeyPair(); 65             RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic(); 66             RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate(); 67  68             Map<String, byte[]> keyMap = new HashMap<String, byte[]>(); 69             keyMap.put(PUBLIC_KEY, publicKey.getEncoded()); 70             keyMap.put(PRIVATE_KEY, privateKey.getEncoded()); 71             return keyMap; 72         } catch (NoSuchAlgorithmException e) { 73             // TODO Auto-generated catch block 74             e.printStackTrace(); 75         } 76         return null; 77     } 78  79     /** 80      * 还原公钥，X509EncodedKeySpec 用于构建公钥的规范 81      *  82      * @param keyBytes 83      * @return 84      */ 85     public static PublicKey restorePublicKey(byte[] keyBytes) { 86         X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(keyBytes); 87  88         try { 89             KeyFactory factory = KeyFactory.getInstance(KEY_ALGORITHM); 90             PublicKey publicKey = factory.generatePublic(x509EncodedKeySpec); 91             return publicKey; 92         } catch (NoSuchAlgorithmException | InvalidKeySpecException e) { 93             // TODO Auto-generated catch block 94             e.printStackTrace(); 95         } 96         return null; 97     } 98  99     /**100      * 还原私钥，PKCS8EncodedKeySpec 用于构建私钥的规范101      * 102      * @param keyBytes103      * @return104      */105     public static PrivateKey restorePrivateKey(byte[] keyBytes) {106         PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(107                 keyBytes);108         try {109             KeyFactory factory = KeyFactory.getInstance(KEY_ALGORITHM);110             PrivateKey privateKey = factory111                     .generatePrivate(pkcs8EncodedKeySpec);112             return privateKey;113         } catch (NoSuchAlgorithmException | InvalidKeySpecException e) {114             // TODO Auto-generated catch block115             e.printStackTrace();116         }117         return null;118     }119 120     /**121      * 加密，三步走。122      * 123      * @param key124      * @param plainText125      * @return126      */127     public static byte[] RSAEncode(PublicKey key, byte[] plainText) {128 129         try {130             Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);131             cipher.init(Cipher.ENCRYPT_MODE, key);132             return cipher.doFinal(plainText);133         } catch (NoSuchAlgorithmException | NoSuchPaddingException134                 | InvalidKeyException | IllegalBlockSizeException135                 | BadPaddingException e) {136             // TODO Auto-generated catch block137             e.printStackTrace();138         }139         return null;140 141     }142 143     /**144      * 解密，三步走。145      * 146      * @param key147      * @param encodedText148      * @return149      */150     public static String RSADecode(PrivateKey key, byte[] encodedText) {151 152         try {153             Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM);154             cipher.init(Cipher.DECRYPT_MODE, key);155             return new String(cipher.doFinal(encodedText));156         } catch (NoSuchAlgorithmException | NoSuchPaddingException157                 | InvalidKeyException | IllegalBlockSizeException158                 | BadPaddingException e) {159             // TODO Auto-generated catch block160             e.printStackTrace();161         }162         return null;163 164     }165 }

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