一次性，加密和解密 [英] One time pad, encryption and decryption

问题描述

您好，我正在尝试使用crytography并尝试这个练习

编写一个程序（最好是Java）生成一个一次性pad，相对大文件的所有
随机数据（比方说1 MB）。程序还应该能够基于
生成的一次性填充来加密/解密文件。

提示：使用以下测试向量来检查您的程序正确加密。

纯文字（ASCII）：每个云都有一个白衬线

OTP（HEX）：6dc72fc595e35dcd38c05dca2a0d2dbd8e2df20b129b2cfa29ad17972922a2

（HEX）：28b14ab7ecc33ea157b539ea426c5e9def0d81627eed498809c17ef9404cc5

我尝试使用随机数字生成器生成一次性填充，因为我需要将它们转换为十六进制形式。

  public static void oneTimePad（）
 { 
 Random ran = new Random（）; 
 String s =0123456789ABCDEF; 
 for（int i = 0; i <100; i ++）
 {
 System.out.print（s.charAt（ran.nextInt（s.length（））））; 
} 
 
 
} 
  

解决方案

p>这里有一个完整的工作示例：

  //将秘密文本转换为字节数组
 final byte [] secret =secret.getBytes（）
 
 final byte [] encoded = new byte [secret.length]; 
 final byte [] decoded = new byte [secret.length]; 
 
 //生成随机密钥（必须交换）
 final byte [] key = new byte [secret.length]; 
 new SecureRandom（）。nextBytes（key）; 
 
 //加密
 for（int i = 0; i  encoded [i] =（byte） key [i]）; 
} 
 
 //解密
 for（int i = 0; i  decoded [i] = encoding [i] ^ key [i]）; 
} 
 
 assertTrue（Arrays.equals（secret，decoded））; 
  

我最好的，

Maciek

Hi I am trying to pick up crytography and had been trying this exercise

Write a program (preferably Java) to generate a one-time pad, which is a relatively large file of all random data (say 1 MB). The program should also be able to encrypt/decrypt files based on the generated one time pad.

Tip: use the following test vector to check if your program does encryption correctly.

Plaintext (ASCII): Every cloud has a silver lining
OTP (HEX): 6dc72fc595e35dcd38c05dca2a0d2dbd8e2df20b129b2cfa29ad17972922a2
ciphertext (HEX): 28b14ab7ecc33ea157b539ea426c5e9def0d81627eed498809c17ef9404cc5

I have tried to generate a one time pad using random number generator as I need to convert them to HEX form. and I am pretty sure I am confused or not tackling it the right way

public static void oneTimePad()
{
    Random ran = new Random();
    String s = "0123456789ABCDEF";
    for(int i = 0; i < 100; i++)
    {   
        System.out.print(s.charAt(ran.nextInt(s.length())));
    }


}

Above would be my one time pad, and I was wondering how any idea how I could implement the encryption using the one time pad and decrypting it.

解决方案

Here you have a full working example:

    // convert secret text to byte array
    final byte[] secret = "secret".getBytes()

    final byte[] encoded = new byte[secret.length];
    final byte[] decoded = new byte[secret.length];

    // Generate random key (has to be exchanged)
    final byte[] key = new byte[secret.length];
    new SecureRandom().nextBytes(key);

    // Encrypt
    for (int i = 0; i < secret.length; i++) {
        encoded[i] = (byte) (secret[i] ^ key[i]);
    }

    // Decrypt
    for (int i = 0; i < encoded.length; i++) {
        decoded[i] = (byte) (encoded[i] ^ key[i]);
    }

    assertTrue(Arrays.equals(secret, decoded));

My best,

Maciek

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