C++ <文本文件的加密与解密>

未加密文本.txt

almost lover

Your fingertips against my skin 
The palm trees swaying in the wind in my chase 
You sang me Spanish lullabies 
The sweetest sadness in your eyes 
Clever trick

I never wanna see you unhappy 
I thought you want the same for me 
Goodbye my almost lover 
Goodbye my hopeless dream 
I'm trying not to think about you 
Can't you just let me be? 
So long my luckless romance 
My back is turned on you 
Should've known you'd bring me heartbreak 
Almost lovers always do

We walked along a crowded street 
You took my hand and danced with me 
In the shade 
And when you left you kissed my lips 
You told me you'd never ever forget these images 
No

I'd never wanna see you unhappy 
I thought you'd want the same for me 
Goodbye my almost lover 
Goodbye my hopeless dream 
I'm trying not to think about you 
Can't you just let me be? 
So long my luckless romance 
My back is turned on you 
Should've known you'd bring me heartbreak 
Almost lovers always do

I cannot go to the ocean 
I cannot try the streets at night 
I cannot wake up in the morning 
Without you on my mind 
So you're gonna and I'm haunted 
And I bet you are just fine 
I'll make it there 
You walk right in and out of my life

Goodbye my almost lover 
Goodbye my hopeless dream 
I'm trying not to think about you 
Can't you just let me be? 
So long my luckless romance 
My back is turned on you 
Should've known you'd bring me heartache 
Almost lovers always do

加密后文本.txt (key = 20)

u!"$()4!$+y'm$*'4z}#{y')}%(4u{u}#()4".4( }#4h|y4%u!"4)'yy(4(,u.}#{4}#4)|y4,}#x4}#4".4w|u(y4m$*4(u#
{4"y4g%u#}(|4!*!!uv}y(4h|y4(,yy)y()4(ux#y((4}#4.$*'4y.y(4W!y+y'4)'}w 
]4#y+y'4,u##u4(yy4.$*4*#|u%%.4]4)|$*
{|)4.$*4,u#)4)|y4(u"y4z$'4"y4[$$xv.y4".4u!"$()4!$+y'4[$$xv.y4".4|$%y!y((4x'yu"4];"4)'.}#{4#$)4)$4)|}# 
4uv$*)4.$*4Wu#;)4.$*4~*()4!y)4"y4vyS4g$4!$#{4".4!*w !y((4'$"u#wy4a.4vuw 4}(4)*'#yx4$#4.$*4g|$*!x;+y4 
#$,#4.$*;x4v'}#{4"y4|yu')v'yu 4U!"$()4!$+y'(4u!,u.(4x$ky4,u! yx4u!$#{4u4w'$,xyx4()'yy)4m$*4)$$ 
4".4|u#x4u#x4xu#wyx4,})|4"y4]#4)|y4(|uxy4U#x4,|y#4.$*4!yz)4.$*4 }((yx4".4!}%
(4m$*4)$!x4"y4.$*;x4#y+y'4y+y'4z$'{y)4)|y(y4}"u{y(4b$];x4#y+y'4,u##u4(yy4.$*4*#|u%%.4]4)|$*
{|)4.$*;x4,u#)4)|y4(u"y4z$'4"y4[$$xv.y4".4u!"$()4!$+y'4[$$xv.y4".4|$%y!y((4x'yu"4];"4)'.}#
{4#$)4)$4)|}# 4uv$*)4.$*4Wu#;)4.$*4~*()4!y)4"y4vyS4g$4!$#{4".4!*w !y((4'$"u#wy4a.4vuw 4}
(4)*'#yx4$#4.$*4g|$*!x;+y4 #$,#4.$*;x4v'}#{4"y4|yu')v'yu 4U!"$()4!$+y'(4u!,u.
(4x$]4wu##$)4{$4)$4)|y4$wyu#4]4wu##$)4)'.4)|y4()'yy)(4u)4#}{|)4]4wu##$)4,u y4*%4}#4)|y4"$'#}#
{4k})|$*)4.$*4$#4".4"}#x4g$4.$*;'y4{$##u4u#x4];"4|u*#)yx4U#x4]4vy)4.$*4u'y4~*()4z}#y4];!!4"u 
y4})4)|y'y4m$*4,u! 4'}
{|)4}#4u#x4$*)4$z4".4!}zy[$$xv.y4".4u!"$()4!$+y'4[$$xv.y4".4|$%y!y((4x'yu"4];"4)'.}#{4#$)4)$4)|}# 
4uv$*)4.$*4Wu#;)4.$*4~*()4!y)4"y4vyS4g$4!$#{4".4!*w !y((4'$"u#wy4a.4vuw 4}(4)*'#yx4$#4.$*4g|$*!x;+y4 
#$,#4.$*;x4v'}#{4"y4|yu')uw|y4U!"$()4!$+y'(4u!,u.(4x$

主程序：
说明：key值等于1至20之间时程序运行正常，大于20解密后的文件格式会错乱且有些数据与源文件不符，暂时没有更好的解决办法。

#include <iostream>
#include <fstream>
#include <cstdlib>

using namespace std;

void encryptFile(ifstream& inFile, ofstream& outFile, int key);
char encryptChar(char c, int key);
void declassifyFile(ifstream& inFile, ofstream& outFile, int key);
char declassifyChar(char c, int key);

int main() {
    ifstream inFile;
    inFile.open("/Users/br/Documents/C:C++/secretCode/secretGardon.txt");
    if (inFile.fail()) {
        cout << "inFile opening failed.";
        exit(EXIT_FAILURE);
    }

    ofstream outFile;
    outFile.open("/Users/br/Documents/C:C++/secretCode/encyptc.txt");
    if (outFile.fail()) {
        cout << "outFile opening failed.";
        exit(EXIT_FAILURE);
    }
    cout << "Enter a key use it a number between 1 and 100: ";
    int key;
    cin >> key;

    encryptFile(inFile, outFile, key);
    inFile.close();
    outFile.close();

    inFile.open("/Users/br/Documents/C:C++/secretCode/encyptc.txt");
    if (inFile.fail()) {
        cout << "inFile opening failed.";
        exit(EXIT_FAILURE);
    }

    outFile.open("/Users/br/Documents/C:C++/secretCode/declassify.txt");
    if (outFile.fail()) {
        cout << "outFile opening failed.";
        exit(EXIT_FAILURE);
    }

    int key1;
    int count = 5;

    do {
        cout << "Enter a key to unlock the file: ";
        cin >> key1;
        count--;

        if (key1 == key)
            declassifyFile(inFile, outFile, key);
        else
            cout << "you have " << count << " times to unlock it." << '\n';
    } while (count != 0 && key1 != key);

    inFile.close();
    outFile.close();

    return 0;
}

void encryptFile(ifstream& inFile, ofstream& outFile, int key) {
    char c, ec;
    while (! inFile.eof()) {
        inFile.get(c);
        ec = encryptChar(c, key);
        outFile.put(ec);
    }
}

char encryptChar(char c, int key) {
    char enChar;

    if (c + key > 126)
        enChar = 32 + ((c + key) - 127);
    else
        enChar = c + key;

    return enChar;
}

void declassifyFile(ifstream& inFile, ofstream& outFile, int key) {
    char c, dec;
    while (! inFile.eof()) {
        inFile.get(c);
        dec = declassifyChar(c, key);
        outFile.put(dec);
    }
}

char declassifyChar(char decChar, int key) {
    decChar -= key;

    if ((decChar > 31 || decChar == 10) && decChar < 126)
        return decChar;
    else
        return decChar - 32 + 127;
}