区分大小写的 Vigenere 密码产生错误的输出
Case sensitive Vigenere cipher produces wrong output
我付出了很多努力来使密码更可靠,以便输出区分大小写。
意思是,如果消息字符串中有大写字母,输出的字符串中该位置将有一个编码的大写字母。例如 InpUT MesSagE
变成 HrhTS WwlReyD
。使用的密钥是 test
.
public String encrypt(String text, final String key) {
int a_num = (int) 'a';
int A_num = (int) 'A';
String output = "";
for (int i = 0, j = 0; i < text.length(); i++) {
int cur = (int) text.charAt(i);
// check for spaces
if (text.charAt(i) == ' ') {
output += " ";
// check for lowercase
} else if (cur >= 'a' && cur < 'z' + 26) {
output += Character.toString((char) ((cur + key.charAt(j) - 2 * 'a') % 26 + 'a'));
j = ++j % key.length();
// check for uppercase between 'N' and 'Z'
} else if (cur >= 'N' && cur < 'Z') {
output += Character.toString((char) ((cur + key.charAt(j) - 2 * 'A') % 26 + 'N' + 7));
j = ++j % key.length();
// check for uppercase between 'A' and 'M'
} else {
output += Character.toString((char) ((cur + key.charAt(j) - 2 * 'A') % 26 + 'A' - 6));
j = ++j % key.length();
}
}
return output;
}
目前,所有小写字母似乎都能正确显示,有些大写字母也能正确显示。我的问题是有时大写是错误的,例如符号将成为输出的一部分,因为我不正确 math/logic.
我非常确定问题出在代码的这些部分中的变量:
((cur + key.charAt(j) - 2 * 'A') % 26 + 'A' - 6));
public String encrypt(String text, final String key) {
// we assume the key is all lower case
// and only inputs are letters and space (could enhance to leave all else alone)
int a_num = (int) 'a'; //unused?
int A_num = (int) 'A';//unused?
String output = "";
for (int i = 0, j = 0; i < text.length(); i++) {
int cur = (int) text.charAt(i);
// check for spaces
if (text.charAt(i) == ' ') {
output += " ";
}
// check for lowercase
else if (cur >= 'a' && cur <= 'z') {
output += Character.toString((char) ((cur + key.charAt(j) - 2 * 'a') % 26 + 'a'));
j = ++j % key.length();
}
// should work for uppercase between 'A' and 'Z'
else {
output += Character.toString((char) ((cur -'A' + key.charAt(j) - 'a') % 26 + 'A'));
j = ++j % key.length();
}
}
return output;
}
我付出了很多努力来使密码更可靠,以便输出区分大小写。
意思是,如果消息字符串中有大写字母,输出的字符串中该位置将有一个编码的大写字母。例如 InpUT MesSagE
变成 HrhTS WwlReyD
。使用的密钥是 test
.
public String encrypt(String text, final String key) {
int a_num = (int) 'a';
int A_num = (int) 'A';
String output = "";
for (int i = 0, j = 0; i < text.length(); i++) {
int cur = (int) text.charAt(i);
// check for spaces
if (text.charAt(i) == ' ') {
output += " ";
// check for lowercase
} else if (cur >= 'a' && cur < 'z' + 26) {
output += Character.toString((char) ((cur + key.charAt(j) - 2 * 'a') % 26 + 'a'));
j = ++j % key.length();
// check for uppercase between 'N' and 'Z'
} else if (cur >= 'N' && cur < 'Z') {
output += Character.toString((char) ((cur + key.charAt(j) - 2 * 'A') % 26 + 'N' + 7));
j = ++j % key.length();
// check for uppercase between 'A' and 'M'
} else {
output += Character.toString((char) ((cur + key.charAt(j) - 2 * 'A') % 26 + 'A' - 6));
j = ++j % key.length();
}
}
return output;
}
目前,所有小写字母似乎都能正确显示,有些大写字母也能正确显示。我的问题是有时大写是错误的,例如符号将成为输出的一部分,因为我不正确 math/logic.
我非常确定问题出在代码的这些部分中的变量:
((cur + key.charAt(j) - 2 * 'A') % 26 + 'A' - 6));
public String encrypt(String text, final String key) {
// we assume the key is all lower case
// and only inputs are letters and space (could enhance to leave all else alone)
int a_num = (int) 'a'; //unused?
int A_num = (int) 'A';//unused?
String output = "";
for (int i = 0, j = 0; i < text.length(); i++) {
int cur = (int) text.charAt(i);
// check for spaces
if (text.charAt(i) == ' ') {
output += " ";
}
// check for lowercase
else if (cur >= 'a' && cur <= 'z') {
output += Character.toString((char) ((cur + key.charAt(j) - 2 * 'a') % 26 + 'a'));
j = ++j % key.length();
}
// should work for uppercase between 'A' and 'Z'
else {
output += Character.toString((char) ((cur -'A' + key.charAt(j) - 'a') % 26 + 'A'));
j = ++j % key.length();
}
}
return output;
}