Some Simple PHP Password Generation Functions

Passwords may well become a thing of the past in the not-so-distant future, as processing power doubles up year on year and makes the cracking of passwords in a brute force manner almost trivial.

This calculator of password complexity against brute force attacks illustrates how easy it is to compromise a password in an offline environment.

Fortunately for us web developers, things take an awful lot longer in an online scenario- due to the fact that the network latency and distance limits the number of password hacking attempts can occur in a reasonable timeframe. Various other layers of protection can be added too, blacklistings IP’s, locking accounts after a number of failed login attempts and generally paying attention nefarious requests.

There’s been numerous instances where a public facing vulnerability has resulted in password crackers gaining access to an entire database of usernames and passwords. The worst cases involve passwords that are not one-way encrypted at all, no computation is necessary to exploit them and unfortunately, can expose users who use the same passwords across different sites.

A not-so-bad cases involve one-way encryption of passwords using what’s considered to be weaker algorithms like MD5 that do not use salted passwords.

Summarily, when storing passwords, you need to use salting, preferably on a per-password basis and use what’s considered to be a secure algorithm. Have a look at this article (and comments) for a more involved look at attack scenarios and how to prevent them. From the user standpoint, using any kind of dictionary word or concatenation of words is asking for trouble, particularly if the database that stores them is not salting passwords.


If you are generating passwords for your users, you will want to have a level of complexity that won’t be subject to brute force attacks. The following code is a simple PHP password generator that will include alphanumeric characters and optionally other printable characters (you can add more if you like). This is good for instances where you need to generate a random password for a user.

This fairly rudimentary function generates passwords of reasonable complexity, depending on length.

For my own personal passwords, it is a pain to be signed up to so many websites and having to memorise or maintain a list. Software like KeePass have sprung up in order to save the hassle of you remembering the long and complex passwords that are desirfed to maintain a good degree of confidence your account(s) are secure.

The following function is similar in notion, passwords do not have to be remembered here, simply the domain name that you use them on:

There is a caveat. Due to some temporal lapse in concentration of some web developers, some password fields insist on restricting what characters are in a password, or insist on certain groups of characters being present. This is fine for preventing people enter overly simple passwords, but can cause issues in my above implementation. For those occasions you may want to just use a part of the hex representation of the hash and calculate that some of the characters should become uppercase.

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