如何使用RSA和AES算法對文件進行加密和解密

Question

我想加密test.txt文件我正在使用此java類進行加密和解密。在我的目錄中，我有三個文件private.txt用於保存私鑰和公共。公鑰和test.txt的txt用於加密。

package EncryptionDecryption; 
    import java.io.BufferedInputStream; 


    public class EncryptionUtil { 

     /** 
     * String to hold name of the encryption algorithm. 
     */ 
     public static final String ALGORITHM = "RSA"; 

     /** 
     * String to hold the name of the private key file. 
     */ 
     public static final String PRIVATE_KEY_FILE = "private.txt"; 

     /** 
     * String to hold name of the public key file. 
     */ 
     public static final String PUBLIC_KEY_FILE = "public.txt"; 


     public static void generateKey() { 
     try { 
      final KeyPairGenerator keyGen = KeyPairGenerator.getInstance(ALGORITHM); 
      keyGen.initialize(1024); 
      final KeyPair key = keyGen.generateKeyPair(); 

      File privateKeyFile = new File(PRIVATE_KEY_FILE); 
      File publicKeyFile = new File(PUBLIC_KEY_FILE); 

      // Create files to store public and private key 
      if (privateKeyFile.getParentFile() != null) { 
      privateKeyFile.getParentFile().mkdirs(); 
      } 
      privateKeyFile.createNewFile(); 

      if (publicKeyFile.getParentFile() != null) { 
      publicKeyFile.getParentFile().mkdirs(); 
      } 
      publicKeyFile.createNewFile(); 

      // Saving the Public key in a file 
      ObjectOutputStream publicKeyOS = new ObjectOutputStream(
       new FileOutputStream(publicKeyFile)); 
      publicKeyOS.writeObject(key.getPublic()); 
      System.out.println("public"+key.getPublic().getEncoded()); 
      publicKeyOS.close(); 

      // Saving the Private key in a file 
      ObjectOutputStream privateKeyOS = new ObjectOutputStream(
       new FileOutputStream(privateKeyFile)); 
      privateKeyOS.writeObject(key.getPrivate()); 
      System.out.println("private"+key.getPrivate().getEncoded()); 
      //System.out.println(key.getPrivate()); 
      privateKeyOS.close(); 
     } catch (Exception e) { 
      e.printStackTrace(); 
     } 

     } 

     public static boolean areKeysPresent() { 

     File privateKey = new File(PRIVATE_KEY_FILE); 
     File publicKey = new File(PUBLIC_KEY_FILE); 

     if (privateKey.exists() && publicKey.exists()) { 
      return true; 
     } 
     return false; 
     } 


     public static byte[] encrypt(byte[]bs, PublicKey key) { 
     byte[] cipherText = null; 
     try { 
      // get an RSA cipher object and print the provider 
      final Cipher cipher = Cipher.getInstance(ALGORITHM); 
      // encrypt the plain text using the public key 
      cipher.init(Cipher.ENCRYPT_MODE, key); 
      cipherText = cipher.doFinal(bs); 
     } catch (Exception e) { 
      e.printStackTrace(); 
     } 
     return cipherText; 
     } 


     public static String decrypt(byte[] text, PrivateKey key) { 
     byte[] dectyptedText = null; 
     try { 
      // get an RSA cipher object and print the provider 
      final Cipher cipher = Cipher.getInstance(ALGORITHM); 

      // decrypt the text using the private key 
      cipher.init(Cipher.DECRYPT_MODE, key); 
      dectyptedText = cipher.doFinal(text); 

     } catch (Exception ex) { 
      ex.printStackTrace(); 
     } 

     return new String(dectyptedText); 
     } 

     public static void main(String[] args)throws IOException { 
      System.out.println("Hai"); 

     try { 

      // Check if the pair of keys are present else generate those. 


      generateKey(); 
      File f=new File("test.txt"); 
      byte[] contents = new byte[(int)f.length()]; 
      BufferedInputStream bis = null; 
      try 
      { 
       bis = new BufferedInputStream(new FileInputStream(f)); 
       DataInputStream dis = new DataInputStream(bis); 
       dis.readFully(contents); 
      } 
      finally 
      { 
       if(bis != null) 
       { 
        bis.close(); 
       } 
      }   


     // final String originalText = "Text to be encrypted"; 


      // Encrypt the string using the public key 
      ObjectInputStream inputStream = new ObjectInputStream(new FileInputStream(PUBLIC_KEY_FILE)); 
      final PublicKey publicKey = (PublicKey) inputStream.readObject(); 
      final byte[] cipherText = encrypt(contents, publicKey); 
      inputStream.close(); 
      // Decrypt the cipher text using the private key. 
      ObjectInputStream inputStream1 = new ObjectInputStream(new FileInputStream(PRIVATE_KEY_FILE)); 
      final PrivateKey privateKey = (PrivateKey) inputStream1.readObject(); 
      final String plainText = decrypt(cipherText, privateKey); 

      // Printing the Original, Encrypted and Decrypted Text 

      System.out.println("Original Text: " + contents.toString()); 
      System.out.println("Encrypted Text: " +cipherText); 
      System.out.println("Decrypted Text: " + plainText); 
      inputStream.close(); 
      inputStream1.close(); 

     } catch (Exception e) { 
      e.printStackTrace(); 
     } 
     finally 
     { 

     } 

     } 
     } 




I got this error when debugging 

I 

    public[B@f73c1 
    private[B@15b9e68 
    javax.crypto.IllegalBlockSizeException: Data must not be longer than 117 bytes 
     at com.sun.crypto.provider.RSACipher.a(DashoA13*..) 
     at com.sun.crypto.provider.RSACipher.engineDoFinal(DashoA13*..) 
     at javax.crypto.Cipher.doFinal(DashoA13*..) 
     at EncryptionDecryption.EncryptionUtil.encrypt(EncryptionUtil.java:122) 
     at EncryptionDecryption.EncryptionUtil.main(EncryptionUtil.java:193) 
    java.lang.IllegalArgumentException: Null input buffer 
     at javax.crypto.Cipher.doFinal(DashoA13*..) 
     at EncryptionDecryption.EncryptionUtil.decrypt(EncryptionUtil.java:147) 
     at EncryptionDecryption.EncryptionUtil.main(EncryptionUtil.java:198) 
    java.lang.NullPointerException 
     at java.lang.String.<init>(String.java:593) 
     at EncryptionDecryption.EncryptionUtil.decrypt(EncryptionUtil.java:153) 
     at EncryptionDecryption.EncryptionUtil.main(EncryptionUtil.java:198) 

Answer 1

有一個很好的基本例子here加密字符串。這個例子使用DES，但我相信原則是一樣的，所以希望能幫助你開始。

您發佈的堆棧跟蹤與this post面臨的問題非常相似。如果你有一個可能爲你提供修復的外觀，那裏有一個被接受的答案。

祝你好運！