//Monalphabetic Cipher

/**Created by:Mihir Vadalia*/

#include

FILE *source,*dest,*kf;

void encrypt();

void decrypt();

void main()

{

int choice;

{

clrscr();

printf("\n\n\t\tMonoalphabetic Cipher\n\nEnter your chice:\n");

printf("1.Encryption\n2.Decryption\n3.Exit.\n\nYour Choice:");

scanf("%d",&choice);

switch(choice)

{

case 1:

encrypt();

break;

case 2:

decrypt();

break;

default:

exit(0);

}

getch();

}while(choice);

}

void encrypt()

{

char k[26]={'/0'},fname[15],ch;

int i,n;

printf("\n\nEnter the name of file to be encrypted:\n");

flushall();

gets(fname);

flushall();

source = fopen(fname,"r");

dest = fopen("Dest.txt","w");

kf = fopen("key.txt","r");

i=0;

while((ch=getc(kf))!=EOF)

{

k[i]=ch;

i++;

}

while ((ch=getc(source))!=EOF)

{

n=(int)ch-97;

for (i=0;i!=n;i++);

putc(k[i],dest);

}

fclose(dest);

fclose(source);

fclose(kf);

printf("\n\nThe file has been encrypted...\n\nThe contents are:\n");

dest=fopen("Dest.txt","r");

while((ch=getc(dest))!=EOF)

printf("%c",ch);

}

void decrypt()

{

char k[26]={'/0'},fname[15],ch;

int i,n;

printf("\n\nEnter the name of file to be decrypted:\n");

flushall();

gets(fname);

flushall();

dest = fopen(fname,"r");

kf = fopen("key.txt","r");

i=0;

while((ch=getc(kf))!=EOF)

{

k[i]=ch;

i++;

}

printf("\nDecrypted contents are : ");

while ((ch=getc(dest))!=EOF)

{

for (i=0;ch!=k[i];i++);

putchar(97+i);

}

fclose(source);

fclose(kf);

}

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