Question

C code: hash program (use the Fowler-Noll-Vo (FNV) hash algorithm)

This is a simple program that you will use in the second part of the assignment. Details of this program is as follows.
A hashing algorithm is simply an algorithm that maps data of an arbitrary size into a hash value of a fixed size. On your VM, you should have a program called ”md5sum”, which computes the MD5 hash of a file (or bytes taken from standard input). One of the most useful things about md5sum is that it allows you to quickly check if two files are identical; it is highly improbable that two different files will have the same md5 hash (while it is certainly possible, you can safely assume that will not happen in our class).

Note that you will not use md5sum in your assignment. Rather, in this assignment, you will implement and use the Fowler-Noll-Vo (FNV) hash algorithm, which is much simpler than MD5. The following outlines the FNV Hash algorithm:

def hash(bytes):
    hash = 0xcbf29ce484222325
    for byte in bytes:

        hash = hash ^ byte

        hash = hash * 0x100000001b3
    return hash

Your program should read from standard input until it reaches an EOF, and output the hash of the bytes it read using your FNV algorithm. You should add your code to hash.c
In the following example, the user typed “ABC”, and then Enter, and then pressed “Ctrl-D” to send the EOF to the program’s standard input:

[jforce@archlinux lab6]$ ./hash
ABC
93a0128ba58da453

The program computed 93a0128ba58da453 as the hash of ‘‘ABC\n’’
Fun fact (Not useful to solve this assignment): Hashes are commonly used in cryptography and computer security. For example, passwords are often hashed before being put into a database; it is never a good idea to store plaintext passwords in a database. Storing plaintext passwords in a database will result in you beingfired. Note that FNV and MD5 hashes are not cryptographically secure.

Start code:

#include <stdio.h>

int main(){
/*
Fill this code in yourself
*/
  
printf("%lx\n", hash);
return 0;
}

Answer 1

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

const size_t Prime = 0x100000001b3;
const size_t Seed = 0xcbf29ce484222325;

int main()
{
printf("Hello, World!\n");
char str[20];
unsigned char *bytes;
size_t hash;
while(1) {
printf("Enter string:");
scanf("%[^\n]%*c", str);
printf(":%s:", str);
bytes = (unsigned char*)str;
hash = Seed;
for (int i = 0; i < strlen(str); i++) {
hash = hash ^ bytes[i];
hash = hash * Prime;
//printf("%02X ", bytes[i]);
}
printf("%lx\n", hash);
}
printf("\n:");
return 0;
}