Francois Berder / Crypto

This library implements some hash and cryptographic algorithms.

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Table of Contents

  1. Computing hash
  2. TODO

This library implements the following algorithms :

  • RC4
  • AES (AES-128, AES-192, AES-256)
  • MD2
  • MD5
  • SHA-1
  • SHA-2 (SHA-224, SHA-256, SHA-384, SHA-512)

The hash algorithms have been optimized for the mbed and you should get decent performance. However, I did not optimize the ciphers.

Information

If you are using SHA-384 or SHA-512, be aware that it produces large binary files and the compilation takes much longer to execute. It may happen that the compiler stops because it timed-out. In this case, just compile again and it should work.

Computing hash

You can compute the hash of some data in two different ways. The first one is the easiest, each hash algorithm has a static method that takes some data and compute the hash from it.

Computing hash using method 1

#include "Crypto.h"
#include "mbed.h"

static const char msg[] = "mbed is great !";

int main()
{
    uint8_t digest[16];
    MD2::computeDigest(digest, (uint8_t*)msg, strlen(msg));
    printf("digest: ");
    for(int i = 0; i < 16; ++i)
        printf("%02x", digest[i]);
    printf("\n");
    
    return 0;
}

The second one is slightly slower (around 2-3% slower) but it allows you to compute the hash of some data in several steps (by calling add function). This is the method you should use if you need to compute the hash from a large source and you don't have enough memory to store it in a single buffer.

Computing hash using method 2

#include "Crypto.h"
#include "mbed.h"

static const char msg[] = "mbed is great !";

int main()
{
    uint8_t digest[16];
    MD2 h;
    h.add((uint8_t*)msg, strlen(msg));
    h.computeDigest(digest);
    printf("digest: ");
    for(int i = 0; i < 16; ++i)
        printf("%02x", digest[i]);
    printf("\n");
    
    return 0;
}

TODO

  • implement DES and 3DES (currently working on it)
  • optimize ciphers
  • implement HMAC
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