java - 如何将字符串转换为位，然后将其分成两半，对一部分执行一些功能，然后与另一部分进行异或，然后使用java进行交换？

Question

是的，这只是 Feistel 密码..我需要实现一个简单的程序来实现它，而不使用任何预先存在的代码。我认为我的主要问题是将字符串转换为位以对其执行一些功能？顺便说一句，我正在使用java，我不是那么专家。请帮我提供任何信息。你认为这可能有帮助..

这是我的代码:

public static String encrypt(String s) {
// convert to bits
int sByte = new BigInteger(s.getBytes()).intValue();
for(int i = 0 ; i<=1 ; i++) {

// split 
String splitS1 = (""+sByte).substring(0,(""+sByte).length()/2);
String splitS2 = (""+sByte).substring((""+sByte).length()/2,(""+sByte).length());

// convert to int for function + xor 
int spl1 = new BigInteger(splitS1.getBytes()).intValue();
int spl2 = new BigInteger(splitS2.getBytes()).intValue();

int F = 0;

// key based on i 
if (i == 0) 
F = spl2 + 0000111; // key 7 

if (i == 1)
F = spl2 + 00001011; // key 11

// xor
int xOr = spl1^F;

// swap
sByte = spl2 + xOr;
}
// convert to String
String AfterEnc = new String(new BigInteger(""+sByte, 2).toByteArray());

return AfterEnc;
}

Answer 1

my main problem is in conversion of string to bit

按如下方式进行:

import java.util.BitSet;

public class Main {
    public static void main(String[] args) {
        String str = "text";
        byte[] strBytes = str.getBytes();
        BitSet strBitSet = BitSet.valueOf(strBytes);
        System.out.println("BitSet: " + strBitSet);
        String strToBinary = bitSetToBinary(strBitSet);
        System.out.println("Binary representation: " + strToBinary);
    }

    static String bitSetToBinary(BitSet bitSet) {
        StringBuilder s = new StringBuilder();
        for (int i = 0; i < bitSet.length(); i++) {
            s.append(bitSet.get(i) == true ? 1 : 0);
        }
        return s.reverse().toString();
    }
}

输出:

BitSet: {2, 4, 5, 6, 8, 10, 13, 14, 19, 20, 21, 22, 26, 28, 29, 30}
Binary representation: 1110100011110000110010101110100

[更新]

注意:我建议您在开头拆分字符串，然后为两部分创建 BitSet，例如

import java.util.BitSet;

public class Main {
    public static void main(String[] args) {
        String str = "text";
        String part1 = str.substring(0, str.length() / 2);
        String part2 = str.substring(str.length() / 2);
        byte[] part1Bytes = part1.getBytes();
        byte[] part2Bytes = part2.getBytes();
        BitSet part1BitSet = BitSet.valueOf(part1Bytes);
        BitSet part2BitSet = BitSet.valueOf(part2Bytes);
        System.out.println("Part1 BitSet: " + part1BitSet);
        System.out.println("Part2 before performing XOR: " + part2BitSet);
        part2BitSet.xor(part1BitSet);// You can create a new BitSet for performing XOR. I am using an existing BitSet for test.
        System.out.println("Part2 after performing XOR: " + part2BitSet);
    }
}

输出:

Part1 BitSet: {2, 4, 5, 6, 8, 10, 13, 14}
Part2 before performing XOR: {3, 4, 5, 6, 10, 12, 13, 14}
Part2 after performing XOR: {2, 3, 8, 12}