Question

C PROGRAMMING

Implement a function (using only #include library) that can encrypt/decrypt with a substitution cipher.

cipher_sub (a, b, c, d)

a is the string that has the data that will be encrypted or decrypted

b is the string that has the result of the encrypt/decrypt

c is the code string used for our substitution cipher (27 entries plus '\0' character)

d is an integer that will pass two constants defined as ENC (encrypt) or DEC (decrypt)

--> The function is supposed to return the character that is in the shifted array at the index (aka what is the character at index z)

**The length of the code is unknown (but can be figured out using '\0' character)

**Assume that strings of 27 (26 letters in the alphabet and the space "_") characters can be called, and that all the characters are unique (never repeated).

PLEASE COMMENT ON YOUR CODE EXPLAINING WHAT WAS DONE

Answer 1

SOLUTION:-

// SIMPLE C PROGRAM TO ENCRYPT AND DECRY P T A STRING //

/*

#include<stdio.h>

int main( )

{

int i, x;

char s t r[100];

print f("\n Please enter a string :\t");

gets(s t r);

print f("\n Please choose following options:\n");

print f("1= Encrypt the string.\n");

print f("2= Decry pt the string .\n");

scan f("%d" ,&x);

//using switch case statements

switch(x)

{

case 1:

for(i = 0; (i< 100 && s t r[i] !='\0');i++)

s t r[i]=s t r[i] +3;

// the key for encryption

print f(" \n decry pt ed string: %s \n",s t r);

break;

default:

print f( " \n Error \n");

}

return 0;

}

*/