Caesar cipher for numbers in C

Question

I want to make a Caesar cipher for numbers. (Add 3 to all digits)

Input: 52 Output:85

Input:954 Output:287

Input: -10457 Output:-43780

I'll be very glad if someone helps me with this.

I tried this but when I input the number less than 5 digits it outputs 3 to beginning

When I input 52 it outputs 33385

#include<stdio.h>
#include<stdlib.h>

int main() {

int number,operation;

printf("Enter the number: ");
scanf("%d",&number);

printf("%d", ((number/10000)+3)%10);
printf("%d", (((number % 10000)/1000)+3)%10);
printf("%d", (((number % 1000)/100)+3)%10);
printf("%d", (((number % 100)/10)+3)%10);
printf("%d\n", ((number % 10)+3)%10);

printf("press 1 to continue or 2 for exit.");
scanf("%d",&operation);

switch(operation) {
    case 1:
            printf("Enter the number: ");
scanf("%d",&number);

printf("%d", ((number/10000)+3)%10);
printf("%d", (((number % 10000)/1000)+3)%10);
printf("%d", (((number % 1000)/100)+3)%10);
printf("%d", (((number % 100)/10)+3)%10);
printf("%d\n", ((number % 10)+3)%10);


        break;


    case 2:


        break;
}


return 0;

}

What have you tried? Where are you having problems? How are you going to decode your encoded numbers? SO is not a coding service. We'll help you fix problems in an honest attempt to solve your problem, but we won't simply write the code for you. (I've not previously seen a Caesar cipher for numbers. It's readily doable as long as you treat the numbers as text — a string of digits — and don't try reading the number as a number. For example, using `scanf("%d", &plain)` would be a bad idea.) — Jonathan Leffler, Dec 08 '19 at 09:02
Probably a [headstart](https://github.com/Saurabh702/caesar-cipher) which works for alphabets, you could try implementing it for numbers — Saurabh P Bhandari, Dec 08 '19 at 09:10

score 4 · Answer 1 · answered Dec 08 '19 at 09:14

Here is the general algorithm:

write the number in ASCII into a buffer,
iterate over the characters in the buffer,
for each character,
- if it's a digit, add 3,
- if the resulting ASCII code is bigger than '9', subtract 10

Writing this algorithm in C is an exercise you should perform yourself as part of your educational process. Skipping this exercise, will prevent you to become smarter.

score 1 · Answer 2 · answered Dec 08 '19 at 09:05

You have first to iterate over every digit of your number.
Then, for each digit, add 3 to the number and use a modulo 10 (% 10) to retrieve only the last digit of your number.
You'll have then to concatenate each digit together to build you caesar-ciphered string.

Caesar cipher for numbers in C

2 Answers2