我正在开发一个加密解密程序，该程序使用修改后的 Vigenére 密码。即我在加密/解密 5 个字母后切换出 Vigenere 方块。如果文本很短但文本较长，它会很好地工作 fgetc() 开始返回无效值，就好像不是我试图解密的文件中实际存在的值一样。有时它开始返回 -1，有时只是无效字符。从某种意义上说，如果您使用文本编辑器检查文件，那里还有其他内容，则无效。如果您运行代码，该文件会创建 2 个调试文件，您可以在其中比较一个文件输出的内容和另一个文件从中获得的内容。这种减速似乎通常发生在 250 多个字符左右，但似乎并没有发生在完全相同的时间点。（我有超过 300 个文件，但它仍然有效）。
加密代码：
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <conio.h>
main()
{
FILE* kuhu;
FILE* kust;
FILE* debug;
int i, pikktekst, sisse, o, u, passwpikk, passk, kus, valija, n;
char failinimi[100], passw[80];
char matr2 [154][154], matr3[154][154];
int matr1[257][257];
debug = fopen("debugsisse.txt", "w");
//maatriks 1
//creates matrix for Vigenere Square
o = 0;
u=0;
for(i=0; o<=255; i++)
{
matr1[o][i]= i+u;
if(matr1[o][i]<0){matr1[o][i]= matr1[o][i]+255 ;
}
if(matr1[o][i]> 255)
{matr1[o][i]=matr1[o][i]-255;}
if(i==256)
{o++; i=0; u++;}
}
algusest:
printf("Tere, Kui soovite teksti programmi sisestada vajutage s kui failist\nsisestada vajutage f, juhul kui soovite v%cljuda vajutage x\n press f from file, s to enter here and x to quit\n", 132);
sisse = getch();
if(sisse == 'x'){exit(0);}
if(sisse != 's' & sisse != 'f'){goto algusest;} //again if invalid input
//juhul kui sisestatakse siia
else if(sisse=='s'){kus =0;
printf("Sisestage faili nimi kuhu soovite kr%cptida\n file where to encrypt:\n", 129); //file where to encrypt
scanf("%s", &failinimi);
kuhu = fopen(failinimi, "w");
printf("Sisestage tekst mida soovite kr%cptida:\n text to encrypt\n", 129); //text to encrypt
//is copied to file to get the length
sisse=0;
pikktekst = 0;
for(i=0; sisse!=13; i++)
{
sisse=getch();
printf("%c", sisse);
pikktekst = i;
fprintf(kuhu, "%c", sisse);
}
fclose(kuhu);
kuhu = fopen (failinimi, "r");
}
//juhul kui failist if from wile
else if(sisse == 'f'){
kus=1;
printf("\nPalun kontrollige et fail asub samas asukohas \nkus programm ja sisestage selle nimi:\n enter name of file:");
scanf("%s", &failinimi);
kuhu=fopen(failinimi, "r");
i=0;
sisse = fgetc(kuhu);
for(pikktekst=0; sisse!=EOF ; pikktekst++) //checks the length of file to declare variables
{sisse = fgetc(kuhu);
}
}
//failist sisse
int kryptikssisse[pikktekst+2], valjund[pikktekst+2]; //declares variables for input/output
rewind(kuhu);
for(i=0; i<pikktekst+1; i++)
{
kryptikssisse[i] = fgetc(kuhu);
}
fclose(kuhu);
//prindib krüptitava asja ning pikkuse
//prints the length of text to encrypt and what it is.
// printf("\nkrüptikssisse on %s\n", kryptikssisse);
// printf("pikkus on %d\n", pikktekst);
//kus toimub krüptimine
//encryption happens here
printf("%d Palun sisestage oma v%chemalt viie t%chem%crgi pikkune salas%cna kr%cptimiseks:\n enter password (min 5)\n",kus, 132, 132, 132, 228, 129);
scanf("%s", passw);
passwpikk = strlen(passw);
while(passwpikk<5)
{printf("Palun sisestage oma v%chemalt viie t%chem%crgi pikkune salas%cna kr%cptimiseks:\n", 132, 132, 132, 228, 129);
scanf("%s", passw);
passwpikk = strlen(passw);
}
//if its from file the output file gets asked here
if(kus != 0){
printf("Sisestage faili nimi kuhu soovite kr%cptida\n", 129);
scanf("%s", &failinimi);}
kuhu = fopen(failinimi, "w");
//maatrikikirjutus
//prints out the matrix
/*
o=0; u=0;
for(i=0; o<=256; i++)
{ if( matr1[o][i] != 13 && matr1[o][i] != 10 ) { fprintf(kuhu, "%d ", matr1[o][i]); }
else { fprintf(kuhu, "ENTER"); }
if(i==257){fprintf(kuhu," %d \n", o); o++; u++; i=0;}
}exit(0);
*/
n=0;
valija=0;
passk = 0;
for(o=0; o<pikktekst; o++)
{
n++;
if(n%5==0) //changes Square after 5 letters
{int x=0, y=0, z=0; // variables to make table
valija++;
if(valija > 255)
{
while(valija>255)
{
valija = valija - 255;
}
}
for(z=0; x<=255; z++) //creates new square, checks that nothing is higher or lower than 255
{
matr1[x][z]= z+y+valija;
if(matr1[x][z]<0)
{matr1[x][z]= matr1[x][z]+255 ;}
if(matr1[x][z]> 255)
{matr1[x][z]=matr1[x][z]-256;}
if(z==256)
{x++; z=0; y++;}
}
}
//gives value to output
valjund[o]=matr1[passw[passk]][kryptikssisse[o]] /*+valija*/;
//checks that output isnt too little or large
while(valjund[o] < 0)
{valjund[o]= valjund[o]+256;
}
while(valjund[o] > 256)
{valjund[o]= valjund[o]-256; }
//prints output into debug file, with extra info AND the file the user specified
fprintf(kuhu, "%c", valjund[o]);
fprintf(debug, "%d : %c (%d) --> %c (%d)\n",n, kryptikssisse[o], kryptikssisse[o], valjund[o], valjund[o]);
passk++;//checks password and resets if neccesary
if(passk>=passwpikk) {passk=0;}
}
fprintf(debug, "%s", kryptikssisse);
system("pause");
fclose(kuhu);
exit(0);
}
解密的代码是：
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <conio.h>
#include <sys/stat.h>
main()
{ FILE* kust;
FILE* kuhu;
FILE* debug;
debug = fopen("debug valja.txt", "w");
fpos_t position;
int i, sisse, passwpikk, u, o, kord, nord, k;
char pw[50], sissef[80], valjaf[80];
int matr1[257][257];
printf("Mis failist soovite dekr%cptida?\n input file\n", 129);
scanf("%s", &sissef);
kust= fopen(sissef, "r");
struct stat st;
stat(sissef, &st);
int size = st.st_size;
printf("Size =%d", size);
printf("Kuhu soovite teksti panna?\n output file\n");
scanf("%s", &valjaf);
kuhu = fopen(valjaf, "wb");
//maatriks 1
//makes Vigenere Table
o = 0;
u=0;
for(i=0; o<=255; i++)
{
matr1[o][i]= i+u;
if(matr1[o][i]<0){matr1[o][i]= matr1[o][i]+255 ;
}
if(matr1[o][i]> 255)
{matr1[o][i]=matr1[o][i]-255;}
if(i==256)
{o++; i=0; u++;}
}
//maatriksikirjutus
//prints Vigenere table
/*o=0; u=0;
for(i=0; o<=256; i++)
{if( matr1[o][i] != 13 && matr1[o][i] != 10 ) { fprintf(kuhu, "%d ", matr1[o][i]); }
else { fprintf(kuhu, "ENTER"); }
if(i==257){fprintf(kuhu," %d \n", o); o++; u++; i=0;}
}exit(0);*/
printf("Palun sisestage oma salas%cna!\npassword\n", 228);
scanf("%s", &pw);
passwpikk = strlen(pw);
//starts encrypting
int valjund=0;
sisse = 0;
sisse = fgetc(kust);
kord=0;
nord=1;
for(o=0; nord<size; nord++){
if(nord%5==0) //changes table
{int x=0, y=0, z=0;
kord++;
if(kord>255)
{while(kord>255)
{
kord= kord - 255;
}
}
for(z=0; x<=255; z++)
{
matr1[x][z]= z+y/*+kord*/;
if(matr1[x][z]<0)
{matr1[x][z]= matr1[x][z]+255 ;}
if(matr1[x][z]> 255)
{matr1[x][z]=matr1[x][z]-256;}
if(z==256)
{x++; z=0; y++;}
}
//prints all matrixes that it uses; please not file can get very large and the programs uses A LOT of time.
/*
FILE* matr;
matr = fopen("maatriksid", "a");
fprintf(matr, "\n\n");
z=0; x=0;
for(i=0; z<=255; i++)
{if( matr1[z][i] != 13 && matr1[z][i] != 10 ) { fprintf(matr, "%d ", matr1[z][i]); }
else { fprintf(matr, "ENTER"); }
if(i==256){fprintf(matr," %d \n", z); z++; x++; i=0;}
}
fclose(matr);
*/
}
i=pw[o];
for( u=0; sisse != matr1[i][u]; u++)
{
}
if(u==0)
{
for( u=1; sisse != matr1[i][u]; u++)
{
}
}
//show when bad things happen
if(matr1[0][u]-kord<0)
{fprintf(debug, "shiiet");}
if(u>256){fprintf(debug, " shit went to hell ");}
valjund = matr1[0][u] - kord ;
/*
while(valjund < 0)
{
valjund= valjund+255;
}
while(valjund > 255)
{
valjund = valjund - 255;
}
*/
//prints stuff out
// note that the debug file prints the int sisse which shows exactly the letter that the program took from the file
fprintf(kuhu ,"%c", valjund);
fprintf(debug,"%d : %c (%d) --> %c (%d) u oli %d \n",nord, sisse, sisse, valjund, valjund, u);
//hoped reopening the file would help
//it didnt
fgetpos(kust, &position);
sisse = fgetc(kust);
if(sisse==-1)
{
fclose(kust);
kust = fopen(sissef, "r");
fsetpos(kust, &position);
sisse= fgetc(kust);
}
//checks password
o++;
if(o>=passwpikk){o=0;}
}
//prints the password at the end of debug file
fprintf(debug,"\n%s", pw);
printf("valmis\n done\n");
system("pause");
exit(0);
}