需要幫助在RSA加密（doFinal）

Question

我想加密和解密使用RSA算法的字符串。這裏的加密工作正常，但問題在於解密。 代碼在DECRYPT方法中達到doFinal時終止。 我輸入錯誤或公鑰和私鑰有問題嗎？ 請給我關於這方面的建議。 謝謝你。

public class rsa 
{ 
private KeyPair keypair;  

public rsa() throws NoSuchAlgorithmException, NoSuchProviderException 
    { 
     KeyPairGenerator keygenerator = KeyPairGenerator.getInstance("RSA"); 
     SecureRandom random = SecureRandom.getInstance("SHA1PRNG", "SUN"); 
     keygenerator.initialize(1024, random); 
     keypair = keygenerator.generateKeyPair(); 
    } 
public String ENCRYPT(String Algorithm, String Data) throws Exception 
{ 
    String alg = Algorithm; 
    String data=Data; 
    byte[] encrypted=new byte[2048]; 
    if(alg.equals("RSA")) 
    { 

     PublicKey publicKey = keypair.getPublic(); 
     Cipher cipher; 
     cipher = Cipher.getInstance("RSA"); 
     cipher.init(Cipher.ENCRYPT_MODE, publicKey); 
     encrypted = cipher.doFinal(data.getBytes()); 
     System.out.println("Encrypted String[RSA] -> " + encrypted); 
    } 
    return encrypted.toString(); 
} 
public String DECRYPT(String Algorithm, String Data) throws Exception 
{ 
    String alg = Algorithm; 
    byte[] Decrypted=Data.getBytes(); 


    if(alg.equals("RSA")) 
    { 

     PrivateKey privateKey = keypair.getPrivate(); 
     Cipher cipher; 
     cipher = Cipher.getInstance("RSA"); 
     cipher.init(Cipher.DECRYPT_MODE, privateKey); 
     byte[] dec = cipher.doFinal(Decrypted); 

     System.out.println("Decrypted String[RSA] -> " + dec.toString()); 

    } 
    return Decrypted.toString(); 
} 
public static void main(String[] args) throws Exception 
{ 
    rsa RSA=new rsa(); 
    RSA.ENCRYPT("RSA", "avinash"); 
    RSA.DECRYPT("RSA","[B@cb7e2c"); 
} 

}

got exception as 

Exception in thread "main" javax.crypto.BadPaddingException: Data must start with zero 
at sun.security.rsa.RSAPadding.unpadV15(Unknown Source) 
at sun.security.rsa.RSAPadding.unpad(Unknown Source) 
at com.sun.crypto.provider.RSACipher.doFinal(RSACipher.java:356) 
at com.sun.crypto.provider.RSACipher.engineDoFinal(RSACipher.java:382) 
at javax.crypto.Cipher.doFinal(Cipher.java:2086) 
at EncryptionProvider.rsa.DECRYPT(rsa.java:56) 
at EncryptionProvider.rsa.main(rsa.java:68) 

加密的字符串[RSA] - > [B @ 4a96a

Answer 1

[B@cb7e2c不是了加密的輸出。這是嘗試在byte []對象上打印或呼叫toString()的結果。 （例如，查看System.out.println(new byte[0]);的結果）

嘗試將加密的byte []直接送回解密函數，並使用new String(dec)來打印結果。如果要查看/保存加密數據爲字符串，請將其編碼爲十六進制或base64。

以下是區別。 byte[]表示一個字節數組。它是二進制數據，一系列8位有符號數字。如果您習慣於僅使用ascii，則一系列byte s和String之間的區別可能看起來微不足道，但有很多方式可以用二進制表示字符串。你所做的加密和解密不關心字符串的外觀，或者數據完全代表字符串;它只是看着比特。

如果要加密字符串，則需要將其轉換爲一系列字節。另一方面，一旦你解密了構成字符串的字節，你就需要將它們轉換回來。 myString.getBytes()和new String(myBytea)通常是有效的，但由於他們只使用默認編碼，所以有點草率。如果Alice的系統使用utf-8和Bob使用的utf-16，她的信息對他來說就沒有多大意義。因此，最好使用myString.getBytes("utf-8")和new String(myBytea,"utf-8")來指定字符編碼。

下面是從項目的一些功能我工作的，具有示範main函數一起：

import java.security.InvalidKeyException; 
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.SecureRandom; 
import java.security.spec.InvalidKeySpecException; 
import java.security.spec.PKCS8EncodedKeySpec; 
import java.security.spec.X509EncodedKeySpec; 

import javax.crypto.BadPaddingException; 
import javax.crypto.Cipher; 
import javax.crypto.IllegalBlockSizeException; 
import javax.crypto.NoSuchPaddingException; 
import javax.xml.bind.DatatypeConverter; 

public class RSAExample { 
    private static byte[] h2b(String hex){ 
     return DatatypeConverter.parseHexBinary(hex); 
    } 
    private static String b2h(byte[] bytes){ 
     return DatatypeConverter.printHexBinary(bytes); 
    } 

    private static SecureRandom sr = new SecureRandom(); 

    public static KeyPair newKeyPair(int rsabits) throws NoSuchAlgorithmException { 
     KeyPairGenerator generator = KeyPairGenerator.getInstance("RSA"); 
     generator.initialize(rsabits, sr); 
     return generator.generateKeyPair(); 
    } 

    public static byte[] pubKeyToBytes(PublicKey key){ 
     return key.getEncoded(); // X509 for a public key 
    } 
    public static byte[] privKeyToBytes(PrivateKey key){ 
     return key.getEncoded(); // PKCS8 for a private key 
    } 

    public static PublicKey bytesToPubKey(byte[] bytes) throws InvalidKeySpecException, NoSuchAlgorithmException{ 
     return KeyFactory.getInstance("RSA").generatePublic(new X509EncodedKeySpec(bytes)); 
    } 
    public static PrivateKey bytesToPrivKey(byte[] bytes) throws InvalidKeySpecException, NoSuchAlgorithmException{ 
     return KeyFactory.getInstance("RSA").generatePrivate(new PKCS8EncodedKeySpec(bytes)); 
    } 

    public static byte[] encryptWithPubKey(byte[] input, PublicKey key) throws IllegalBlockSizeException, BadPaddingException, InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException { 
     Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding"); 
     cipher.init(Cipher.ENCRYPT_MODE, key); 
     return cipher.doFinal(input); 
    } 
    public static byte[] decryptWithPrivKey(byte[] input, PrivateKey key) throws IllegalBlockSizeException, BadPaddingException, InvalidKeyException, NoSuchAlgorithmException, NoSuchPaddingException { 
     Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding"); 
     cipher.init(Cipher.DECRYPT_MODE, key); 
     return cipher.doFinal(input); 
    } 


    public static void main(String[] args) throws Exception { 
     KeyPair kp = newKeyPair(1<<11); // 2048 bit RSA; might take a second to generate keys 
     PublicKey pubKey = kp.getPublic(); 
     PrivateKey privKey = kp.getPrivate(); 
     String plainText = "Dear Bob,\nWish you were here.\n\t--Alice"; 
     byte[] cipherText = encryptWithPubKey(plainText.getBytes("UTF-8"),pubKey); 
     System.out.println("cipherText: "+b2h(cipherText)); 
     System.out.println("plainText:"); 
     System.out.println(new String(decryptWithPrivKey(cipherText,privKey),"UTF-8")); 
    } 
} 

Answer 2

「[B @ 4a96a」是不加密的字符串。這是字符串的數據。真正的加密發生在這裏

//add this line to your code, it will work fine. 
"String encryptedValue = new BASE64Encoder().encode(encrypted);" 

現在打印encryptedValue查看加密結果。