* @param nchallenge Size of challenge
* @param password Password
* @param algo Algorithm to use
* @param nchallenge Size of challenge
* @param password Password
* @param algo Algorithm to use
*
* Computes H(challenge|password) and returns it as a newly allocated hex
* string, or returns NULL on error.
*
* Computes H(challenge|password) and returns it as a newly allocated hex
* string, or returns NULL on error.