MD5Γ±as—prefijo-o-de-sufijo unlike what others said, it does matter! and as @einstein if you care useΒ HMAC.

why prefix is bad, because one can calculate the intermediate state of the checksum up to the given fixed salt prefix. then start calculating the rest in parallel. In summaryΒ phrase+saltΒ is more secure thanΒ salt+phrase, butΒ HMAC(salt, phrase)Β is even better. \