从文件中读取加密数据

Question

我正在阅读关于使用私钥进行加密的IBM教程。我写下如下代码

import java.security.*; 
import javax.crypto.*; 

// encrypt and decrypt using the DES private key algorithm 

public class PrivateExample { 

    public static void main (String[] args) throws Exception { 
    String text=new String(); 
    text="THIS IS AN ENCRYPTION TEST"; 
    byte[] plainText = text.getBytes("UTF8"); 

    // get a DES private key 
    System.out.println("\nStart generating DES key"); 
    KeyGenerator keyGen = KeyGenerator.getInstance("DES"); 
    keyGen.init(56); 
    Key key = keyGen.generateKey(); 
    System.out.println("Finish generating DES key"); 

    // get a DES cipher object and print the provider 
    Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding"); 
    System.out.println("\n" + cipher.getProvider().getInfo()); 
    // 
    // encrypt using the key and the plaintext 
    System.out.println("\nStart encryption"); 
    cipher.init(Cipher.ENCRYPT_MODE, key); 
    byte[] cipherText = cipher.doFinal(plainText); 
    System.out.println("Finish encryption: "); 
    System.out.println(new String(cipherText, "UTF8")); 

    // 
    // decrypt the ciphertext using the same key 
    System.out.println("\nStart decryption"); 
    cipher.init(Cipher.DECRYPT_MODE, key); 
    byte[] newPlainText = cipher.doFinal(cipherText); 
    System.out.println("Finish decryption: "); 

    System.out.println(new String(newPlainText, "UTF8")); 
    } 
} 

上面的代码很好用。我能够看到结果和一切。但我想修改它如下，以便我可以将cipherText存储在文件中。然后另一个程序从文件中读取加密的文本并对其进行解密。以下是我迄今为止所做的，但我无法理解如何继续。只有一点点提示如何进行将有所帮助。

import java.security.*; 
import javax.crypto.*; 

// encrypt and decrypt using the DES private key algorithm 
public class PrivateExample { 

    public static void main (String[] args) throws Exception { 
    String text=new String(); 
    text="This is an encryption test"; 

    byte[] plainText = text.getBytes("UTF8"); 

    // get a DES private key 
    System.out.println("\nStart generating DES key"); 
    KeyGenerator keyGen = KeyGenerator.getInstance("DES"); 
    keyGen.init(56); 
    Key key = keyGen.generateKey(); 
    System.out.println("Finish generating DES key"); 
    // 
    // get a DES cipher object and print the provider 
    Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding"); 
    System.out.println("\n" + cipher.getProvider().getInfo()); 
    // 
    // encrypt using the key and the plaintext 
    System.out.println("\nStart encryption"); 
    cipher.init(Cipher.ENCRYPT_MODE, key); 
    byte[] cipherText = cipher.doFinal(plainText); 
    System.out.println("Finish encryption: "); 
    System.out.println(new String(cipherText, "UTF8")); 

    //Now writing to an ouput file the cipherText 
    try{ 
     FileOutputStream fs=new FileOutputStream("c:/test.txt"); 
     fs.write(cipherText); 
    }catch(Exception e){ 
     e.printStackTrace(); 
    } 
//How to proceed from here 

} 
} 

该程序的工作已经完成。它已成功将加密的字符串写入文件。新程序只需要解密数据。如何从文件读取加密的字节？新程序显然不知道原始字符串是什么，但我将使用与算法中相同的密钥。请帮忙！我是新来的加密

Answer 1

这里是你如何编写到一个文件：

 //Write your key to an output file. 
     byte[] keyAsByte = key.getEncoded(); 
     FileOutputStream keyfos = new FileOutputStream("key.txt"); 
     keyfos.write(keyAsByte); 
     keyfos.close(); 

我不会建议把钥匙在同一个文件中的加密文本。

这里是你如何阅读ecrypted文本和关键背部和解密：

//Read your key 
    FileInputStream keyFis = new FileInputStream("key.txt"); 
    byte[] encKey = new byte[keyFis.available()]; 
    keyFis.read(encKey); 
    keyFis.close(); 
    Key keyFromFile = new SecretKeySpec(encKey, "DES"); 
    //Read your text 
    FileInputStream encryptedTextFis = new FileInputStream("test.txt"); 
    byte[] encText = new byte[encryptedTextFis.available()]; 
    encryptedTextFis.read(encText); 
    encryptedTextFis.close(); 
    //Decrypt 
    Cipher decrypter = Cipher.getInstance("DES/ECB/PKCS5Padding"); 
    decrypter.init(Cipher.DECRYPT_MODE, keyFromFile); 
    byte[] decryptedText = decrypter.doFinal(encText); 
    //Print result 
    System.out.println("Decrypted Text: " + new String(decryptedText)); 

注：我没有使用相同的路径，你写的信息。