Arduino & Python MD5

Question

Well I tried hashing a string or at least a set of numbers in Python and compare it with the one generated using the MD5 Library updated by Scott MacVicar on the Arduino but the results I get are differents.

Arduino Code:

#include <MD5.h> 

void setup()
{
   //initialize serial
   Serial.begin(9600);
   //give it a second
   delay(1000);
   //generate the MD5 hash for our string
   unsigned char* hash=MD5::make_hash("hello");
   //generate the digest (hex encoding) of our hash
   char *md5str = MD5::make_digest(hash, 16);
   //print it on our serial monitor
   Serial.println(md5str);
}

Result: 5d41402abc4b2a76b9e4080020008c00

Python Code:

from hashlib import md5

m = md5('hello').hexdigest()
print m    

Result: 5d41402abc4b2a76b9719d911017c592

From what I can see in every attempt is that the difference comes at the last 14 characters. But the length of the generated hashes are the same!

What am I doing wrong?? Thanks

Edit:

I used a command from the terminal and got:

echo -n 'hello' | openssl md5

Result: 5d41402abc4b2a76b9719d911017c592

Which makes me think that the root of the problem is in the arduino code

Answer 1

I'm going to assume that you are using the MD5 library from here: https://github.com/tzikis/ArduinoMD5/

It looks like that library has a bug. The MD5::make_hash() function returns a pointer to memory on the stack. Some of that memory must be being altered before the call to make_digest() so the resulting digest is partially wrong.