mcu-csiphash-2-4

SipHash is a family of pseudorandom functions (a.k.a. keyed hash functions) optimized for speed on short messages.

Target applications include network traffic authentication and defense against hash-flooding DoS attacks.

SipHash is secure, fast, and simple (for real):

• SipHash is simpler and faster than previous cryptographic algorithms (e.g. MACs based on universal hashing)
• SipHash is competitive in performance with insecure non-cryptographic algorithms (e.g. MurmurHash)

~ SipHash: a fast short-input PRF

The library implements SipHash PRF for C. The implementation does not utilize 64-bit integer arithmetics, thus it can be used in projects for small microcontrollers.

Implemented algorithm version uses 128-bit key to produce 64-bit hash of the provided data of arbitrary length.

This library is strongly inspired by the SipHash_2_4 C++ library for 8bit Atmel processors authored by Matthew Ford. Actually, all the core logic of the SipHash algorithm is sourced from there. The following is the copyright disclosure of the SipHash_2_4 library author

(c)2013 Forward Computing and Control Pty. Ltd. 
www.forward.com.au
This code may be freely used for both private and commercial use.
Provide this copyright is maintained.

Usage

#include "siphash.h"

void siphash(uint8_t *hash,
             const uint8_t *data,
             const size_t len,
             const uint8_t *key)

Calculated hash of provided data will be stored in hash. Length of the data is passed as len. Hash is calculated under the key provided as 16 element array of uint8_t type. Calculated hash is stored in little-endian order.

Simple usage example is provided in src/example.c.

#include "siphash.h"
#include <string.h>
#include <stdio.h>

void hexdump(const uint8_t * data, const size_t len) {
    unsigned int i;
    for (i = 0; i < len; i++)
        printf("0x%02x ",data[i]);
    printf("\n");
}

unsigned int main() {
    
    uint8_t hash[8];
    uint8_t key[] = {0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38,
                     0x39, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36};
    char *data = "Hello world!";
    
    siphash(hash, (const uint8_t *) data, strlen(data), key);
    
    printf("Data:\t%s\n", data);
    printf("Key:\t"); hexdump(key, (size_t) 16);
    printf("Hash:\t"); hexdump(hash, (size_t) 8);
    
    return 0;
    
}

The example can be compiled by invoking

$ make example

$ ./bin/example
Data:	Hello world!
Key:	0x31 0x32 0x33 0x34 0x35 0x36 0x37 0x38 0x39 0x30 0x31 0x32 0x33 0x34 0x35 0x36 
Hash:	0x93 0x6b 0x84 0x0f 0x09 0x30 0x61 0x22

Testing

To perform the tests, run

$ make test

Extras

The extras folder contains some additional utilities. They will not be documented to a greater extent than the comments in the source files.

License

This code is released under the MIT license.