RSA密鑰的數據類型轉換：由合法的string到PublicKey或PrivateKey

給定base64編碼的RSA公鑰和私鑰，下面兩段代碼可以將string類型轉換為PublicKey和PrivateKey類型，后面會給出完整的測試程序。至於如何將其他形式（如16進制編碼string或byte之類的）轉換為base64 string就很簡單了，可以使用Base64那個庫，自己下個jar包，里面有encode和decode之類的方法，hex轉base64網上也可以搜到。

轉換代碼如下：

 public static PublicKey getPublicKey(String key) throws Exception {
             byte[] keyBytes;
             keyBytes = (new BASE64Decoder()).decodeBuffer(key);
             X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
             KeyFactory keyFactory = KeyFactory.getInstance("RSA");
             PublicKey publicKey = keyFactory.generatePublic(keySpec);
             return publicKey;
       }

public static PrivateKey getPrivateKey(String key) throws Exception {
            byte[] keyBytes;
            keyBytes = (new BASE64Decoder()).decodeBuffer(key);
            PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);
            KeyFactory keyFactory = KeyFactory.getInstance("RSA");
            PrivateKey privateKey = keyFactory.generatePrivate(keySpec);
            return privateKey;
      }

注意：不是隨便敲一串字母就可以作為密鑰string使用的，需要用嚴格的代碼生成公鑰串和私鑰串。

 

完整的程序如下：

程序中包含密鑰轉換、加密和簽名三個部分。

  1 package pack1;

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.Signature;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

import javax.crypto.Cipher;

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

import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;
 
 
public class RSAtest{
    public static final String KEY_ALGORITHM="RSA";
    public static final String SIGNATURE_ALGORITHM="MD5withRSA";
    private static final int KEY_SIZE=1024;
    private static final String PUBLIC_KEY="RSAPublicKey";
    private static final String PRIVATE_KEY="RSAPrivateKey";
    public static String str_pubK = "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCqPvovSfXcwBbW8cKMCgwqNpsYuzF8RPAPFb7LGsnVo44JhM/xxzDyzoYtdfNmtbIuKVi9PzIsyp6rg+09gbuI6UGwBZ5DWBDBMqv5MPdOF5dCQkB2Bbr5yPfURPENypUz+pBFBg41d+BC+rwRiXELwKy7Y9caD/MtJyHydj8OUwIDAQAB";
    public static String str_priK = "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";
      /**
       * 使用getPublicKey得到公鑰,返回類型為PublicKey
       * @param base64 String to PublicKey
       * @throws Exception
       */
      public static PublicKey getPublicKey(String key) throws Exception {
            byte[] keyBytes;
            keyBytes = (new BASE64Decoder()).decodeBuffer(key);
            X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
            KeyFactory keyFactory = KeyFactory.getInstance("RSA");
            PublicKey publicKey = keyFactory.generatePublic(keySpec);
            return publicKey;
      }
      /**
       * 轉換私鑰
       * @param base64 String to PrivateKey
       * @throws Exception
       */
      public static PrivateKey getPrivateKey(String key) throws Exception {
            byte[] keyBytes;
            keyBytes = (new BASE64Decoder()).decodeBuffer(key);
            PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);
            KeyFactory keyFactory = KeyFactory.getInstance("RSA");
            PrivateKey privateKey = keyFactory.generatePrivate(keySpec);
            return privateKey;
      }

      //***************************簽名和驗證*******************************
      public static byte[] sign(byte[] data) throws Exception{
        PrivateKey priK = getPrivateKey(str_priK);
          Signature sig = Signature.getInstance(SIGNATURE_ALGORITHM);        
          sig.initSign(priK);
          sig.update(data);
          return sig.sign();
      }
      
      public static boolean verify(byte[] data,byte[] sign) throws Exception{
          PublicKey pubK = getPublicKey(str_pubK);
          Signature sig = Signature.getInstance(SIGNATURE_ALGORITHM);
          sig.initVerify(pubK);
          sig.update(data);
          return sig.verify(sign);
      }
      
      //************************加密解密**************************
      public static byte[] encrypt(byte[] bt_plaintext)throws Exception{
          PublicKey publicKey = getPublicKey(str_pubK);
          Cipher cipher = Cipher.getInstance("RSA");
          cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        byte[] bt_encrypted = cipher.doFinal(bt_plaintext);
        return bt_encrypted;
      }
      
      public static byte[] decrypt(byte[] bt_encrypted)throws Exception{
        PrivateKey privateKey = getPrivateKey(str_priK);
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE, privateKey);
        byte[] bt_original = cipher.doFinal(bt_encrypted);
        return bt_original;
      }
      //********************main函數：加密解密和簽名驗證*********************
      public static void main(String[] args) throws Exception {
            String str_plaintext = "這是一段用來測試密鑰轉換的明文";
            System.err.println("明文："+str_plaintext);
            byte[] bt_cipher = encrypt(str_plaintext.getBytes());
            System.out.println("加密后："+Base64.encodeBase64String(bt_cipher));
            
            byte[] bt_original = decrypt(bt_cipher);
            String str_original = new String(bt_original);
            System.out.println("解密結果:"+str_original);
            
            String str="被簽名的內容";
            System.err.println("\n原文:"+str);
            byte[] signature=sign(str.getBytes());
            System.out.println("產生簽名："+Base64.encodeBase64String(signature));
            boolean status=verify(str.getBytes(), signature);
            System.out.println("驗證情況："+status);
      }
 
}

曾經在百度知道上尋求過這個問題，一直都沒能很好的解決。今日coding測試成功，來分享一下，技術有限，不足之處望指正。。。。。。by SHADOW.Delta