所有UTF-8字符的Java中的Vigenère密码 [英] Vigenère cipher in Java for all UTF-8 characters

问题描述

我有一个简单的功能，通过Java中的Vigenère加密字符串。我省略了解密，因为这只是一个 - ，而不是在计算新值的行中的+。

I have this simple function for encrypting strings via Vigenère in Java. I omitted the decryption as this is just a "-" instead of the "+" in the line where the new value is calculated.

但是此函数仅适用于正常字母AZ。如何更改函数，以便它支持小写字母以及大写字母和所有其他UTF-8字符？

But this function works only for the normal alphabet A-Z. How can I change the function so that it supports lowercase letters as well as uppercase letters and all other UTF-8 chars?

public static String vigenere_encrypt(String plaintext, String key) {
    String encryptedText = "";
    for (int i = 0, j = 0; i < plaintext.length(); i++, j++) {
        if (j == key.length()) { j = 0; } // use key again if end reached
        encryptedText += (char) ((plaintext.charAt(i)+key.charAt(j)-130)%26 + 65);
    }
    return encryptedText;
}

非常感谢您的帮助！

推荐答案

另一个答案，做Vigenere密码在上&小写字符，只需插入其他字符。使用此技术可创建多组要编码的字符。

Another answer, that does do the Vigenere cipher on upper & lower case characters, simply inserting the other characters. Use this technique to create multiple groups of characters to encode.

public static String vigenere(String plaintext, String key, boolean encrypt) {

    final int textSize = plaintext.length();
    final int keySize = key.length();

    final int groupSize1 = 'Z' - 'A' + 1; 
    final int groupSize2 = 'z' - 'a' + 1;
    final int totalGroupSize = groupSize1 + groupSize2;

    final StringBuilder encryptedText = new StringBuilder(textSize);
    for (int i = 0; i < textSize; i++) {
        final char plainChar = plaintext.charAt(i);

        // this should be a method, called for both the plain text as well as the key
        final int plainGroupNumber; 
        if (plainChar >= 'A' && plainChar <= 'Z') {
            plainGroupNumber = plainChar - 'A';
        } else if (plainChar >= 'a' && plainChar <= 'z') {
            plainGroupNumber = groupSize1 + plainChar - 'a';
        } else {
            // simply leave spaces and other characters
            encryptedText.append(plainChar);
            continue;
        }

        final char keyChar = key.charAt(i % keySize);
        final int keyGroupNumber; 
        if (keyChar >= 'A' && keyChar <= 'Z') {
            keyGroupNumber = keyChar - 'A';
        } else if (keyChar >= 'a' && keyChar <= 'z') {
            keyGroupNumber = groupSize1 + keyChar - 'a';
        } else {
            throw new IllegalStateException("Invalid character in key");
        }

        // this should be a separate method
        final int cipherGroupNumber;
        if (encrypt) {
            cipherGroupNumber = (plainGroupNumber + keyGroupNumber) % totalGroupSize;
        } else {
            // some code to go around the awkward way of handling % in Java for negative numbers
            final int someCipherGroupNumber = plainGroupNumber - keyGroupNumber;
            if (someCipherGroupNumber < 0) {
                cipherGroupNumber = (someCipherGroupNumber + totalGroupSize);
            } else {
                cipherGroupNumber = someCipherGroupNumber;
            }
        }

        // this should be a separate method
        final char cipherChar;
        if (cipherGroupNumber < groupSize1) {
            cipherChar = (char) ('A' + cipherGroupNumber);
        } else {
            cipherChar = (char) ('a' + cipherGroupNumber - groupSize1);
        }
        encryptedText.append(cipherChar);
    }

    return encryptedText.toString();
}

同样，这是不安全的代码，不要在你的键中使用太多的A字符:)但是字符编码应该是声音。

Again, this is unsafe code as the cipher used has been broken for ages. Don't use too many 'A' characters in your keys :) But the character encoding should be sound.

这篇关于所有UTF-8字符的Java中的Vigenère密码的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！