Project: File Encryption Problem Description: Suppose an encrypted file was crea

Question

Project: File Encryption

Problem Description:

Suppose an encrypted file was created using the encoding/decoding scheme . Each letter is substituted by some other letter according to a given mapping as shown below.

String letters = "abcdefghijklmnopqrstuvwxyz";

String enc = "kngcadsxbvfhjtiumylzqropwe";

For example, every 'a' becomes a 'k' when encoding a text, and every 'k' becomes an 'a' when decoding. You will write a program, encode or decode a File, and then encodes or decodes the File using the mapping above. Capital letters are mapped the same way as the lower case letters above, but remain capitalized. For example, every 'A' becomes 'K' when encoding a file, and every 'K' becomes an 'A' when decoding. Numbers and other characters are not encoded and remain the same.

Write a program to read a file and encode the file to an encrypted file. And write a program to get an encrypted file and decode to original file. Your program should prompt the user to enter an input file name and an output file name

What should you do?

Ask for input file name/ output file name (encrypted file). The encrypt using above encode/decode.

Ask for encrypted file and decoded to original input file.

Explanation / Answer

Answer for Question:

1. Read the input file from console. and read the charecter by charecter if it matching the decrypt charcter string letters replace those with letter.

2. Write the data into another file called output file

3. See the below code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
int main()
{
char letters[]={"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"};
char enlet[]= {"kngcadsxbvfhjtiumylzqropweKNGCADSXBVFHJTIUMYLZQROPWE"};
char infile[20];
char outfile[20];
char ch;
int i;

FILE *org, * enc, *dec;

printf("Enter file name (***.txt) : ");
gets(infile);

printf("Enter saving file name (***.txt) : ");
gets(outfile);

org = fopen(infile,"r");
enc = fopen(outfile,"w+");

while((ch=fgetc(org))!=EOF)
{
for(i=0;i<52;i++)
{
if ( letters[i]==ch )
{
ch = enlet[i];
break;
}
}
fputc(ch,enc);
}
fclose(org);
fclose(enc);

return 0;
}

Input:

helloworldhowareyou

Output:

xahhioiyhcxiokyawiq

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