$)$:

Detective

Download detective.c here

Or$,$ copy these file$($s$)$ to your CSE account using the following command:

$$1511$ fetch$-$activity detective

Your mission $($if you choose to accept it$)$ is to complete the program

to decipher encoded messages.

Over the past few months UNSW Security Society has found seemingly normal messages paired with random numbers.

To help you solve this challenge we have created the program detective. $c$ that reads in the message and numbers,

storing them in a struct array.

We have been lucky enough to find one decoded message:

Encoded Message: muahahaha$\_$we're$\_$so$\_$evil#$\_$GNTY

Secret Numbers: $7-23-3-6-13-22-24-2-16-4-14-18-20-11-9-28-21-1-27-8-0-26-12-5-10-15-25-19-17$

Deciphered Message: haha$\_$we$\_$are$\_$TeasiNG$\_$You

Our observations from this are:

Messages seem to end with a

There are always the same number of letters as there are numbers.

Letters maintain their case between their encoded and deciphered message.

Each number is unique counting from $0$ to $n-1($where $n$ is the number of letters$).$

We wish you luck detective!

HINT:

By using the first secret number as an index into the encoded message we find the first letter of the secret

message. I wonder if this pattern can continue? Writing out each number and its associated letter may assist

in solving the cypher.

Examples Assumptions$/$Restrictions$/$Clarifications

The maximum number of characters is $100.$

The number of characters in the encrypted message and the amount of secret numbers are the same.

The case of each letter is preserved in translation.

Messages will end with a

$//$ Detective

$//$ detective.c

$//$

$//$ This program was written by YOUR$-$NAME$-$HERE $($z$5555555)$

$//$ on INSERT$-$DATE$-$HERE

$//$

$//$ A program to decipher hidden messages in enemy codes.

#include

#define MAX$\_$SIZE $100$

struct code $\{$

char letter;

int number;

$\}$;

int main$($void$)\{$

$////////////////$ DO NOT CHANGE ANY OF THE CODE BELOW HERE $//////////////////$

struct code message$[$MAX$\_$SIZE$]$;

$//$ read in message

printf$("$Please enter Encrypted Message: $")$;

int i $=0$;

char letter;

scanf$("\%$c$",$ &letter$)$;

while $($letter $!=\text{'}$

$\text{'})\{$

message$[$i$].$letter $=$ letter;

scanf$("\%$c$",$ &letter$)$;

i$++$;

$\}$

$//$ read in numbers

printf$("$Please enter Secret Numbers: $")$;

int j $=0$;

int number;

scanf$("\%$d$",$ &number$)$;

message$[$j$].$number $=$ number;

j$++$;

while $($j $!=$ i$)\{$

scanf$("-\%$d$",$ &number$)$;

message$[$j$].$number $=$ number;

j$++$;

$\}$

$////////////////$ DO NOT CHANGE ANY OF THE CODE ABOVE HERE $//////////////////$

$////////////////////////////////////////////////////////////////////////////$

$/////////////////////$ ONLY WRITE CODE BELOW HERE $///////////////////////////$

$////////////////////////////////////////////////////////////////////////////$

$//$ TODO: Use the message array to reveal the secret message!

$////////////////////////////////////////////////////////////////////////////$

$/////////////////////$ ONLY WRITE CODE ABOVE HERE $///////////////////////////$

$////////////////////////////////////////////////////////////////////////////$

return $0$;

$\}$