英文:
Vigenere Cipher Algorithm In Java - Decrypted Message to Plaintext
问题
import java.util.Scanner;
public class VigenereCipher {
public static void main(String arg[]) {
String message = "";
String keyword = "KISWAHILI";
Scanner sc = new Scanner(System.in);
System.out.println("Enter a message: ");
message = sc.nextLine();
char msg[] = message.toCharArray();
int msgLength = msg.length;
char key[] = new char[msgLength];
char decryptedText[] = new char[msgLength];
for (int i = 0, j = 0; i < msgLength; i++, j++) {
if (j == keyword.length()) {
j = 0;
}
key[i] = keyword.charAt(j);
}
// Decryption Code
for (int i = 0; i < msgLength; i++) {
decryptedText[i] = (char) (((msg[i] - key[i] + 26) % 26) + 'A');
}
System.out.println("Decrypted Message: " + String.valueOf(decryptedText));
System.out.println("Keyword: " + keyword);
System.out.println("Plaintext: " + String.valueOf(decryptedText));
}
}
英文:
I am currently trying to write the Vigenere Cipher algorithm in Java. I have to change the decrypted message to the plaintext but having trouble. Below is what I have so far.
When I run it, the message is not deciphered properly.
import java.util.Scanner;
public class VigenereCipher {
public static void main(String arg[]) {
String message = "";
String keyword = "KISWAHILI";
Scanner sc = new Scanner(System.in);
System.out.println("Enter a message: ");
message = sc.nextLine();
char msg[] = message.toCharArray();
int msgLength = msg.length;
char key[] = new char [msgLength];
char decryptedText[] = new char[msgLength];
for(int i = 0, j = 0; i < msgLength; i++, j++) {
if(j == keyword.length()) {
j = 0;
}
key[i] = keyword.charAt(j);
}
// Decryption Code
for(int i =0; i < msgLength; i++) {
decryptedText[i] = (char)(((key[i] + 26) % 26) + 'A');
}
System.out.println("Decrypted Message: " + message);
System.out.println("Keyword: " + keyword);
System.out.println("Plaintext: " + String.valueOf(decryptedText));
}
}
答案1
得分: 1
代码部分已翻译如下：
似乎在填充key数组时需要跳过空格：
for (int i = 0, j = 0; i < msgLength; i++) {
if (msg[i] == ' ') {
key[i] = ' ';
} else {
key[i] = keyword.charAt(j++ % keyword.length());
}
}
System.out.println("关键消息： " + new String(key));
类似地，在解密循环中也需要考虑空格。并且解密需要进行修复：
for (int i = 0; i < msgLength; i++) {
char c = msg[i];
decryptedText[i] = c == ' ' ? c : (char)(((msg[i] - key[i] + 26) % 26) + 'A');
}
应用这些更改后，输出如下所示：
关键消息： KISW AH ILIKI SW AHILIKIS WAH ILI KISW AHILIKISW AHIL IKIS
加密消息： XQKP IZ IMWEB LK AUVZCXKW PHL VPE RIKD ASOZZSBZI TOIE ESTD
关键词： KISWAHILI
明文： NIST IS ABOUT TO ANNOUNCE THE NEW HASH ALGORITHM THAT WILL
英文:
It seems that whitespaces need to be skipped while populating key array:
for (int i = 0, j = 0; i < msgLength; i++) {
if (msg[i] == ' ') {
key[i] = ' ';
} else {
key[i] = keyword.charAt(j++ % keyword.length());
}
}
System.out.println("Key Message: " + new String(key));
Similarly, it needs to be taken into account in the decrypting loop.
And decryption has to be fixed:<br/>
D<sub>i</sub> = (M<sub>i</sub> - K<sub>i</sub> + 26 ) mod 26
for (int i =0; i < msgLength; i++) {
char c = msg[i];
decryptedText[i] = c == ' ' ? c : (char)(((msg[i] - key[i] + 26) % 26) + 'A');
}
Upon applying these changes, the output is as follows:
Key Message: KISW AH ILIKI SW AHILIKIS WAH ILI KISW AHILIKISW AHIL IKIS
Encrypted Message: XQKP IZ IMWEB LK AUVZCXKW PHL VPE RIKD ASOZZSBZI TOIE ESTD
Keyword: KISWAHILI
Plaintext: NIST IS ABOUT TO ANNOUNCE THE NEW HASH ALGORITHM THAT WILL
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