From: Jamie Macey <jamie.macey@...>
Date: 2008-12-29T21:19:45+09:00
Subject: Re: Options to generate small, kind of unique, human-readable tokens 	(like "V0cM9tnV") ?

On Dec 29, 4:44 am, Thibaut Barrère <thibaut.barr...@gmail.com> wrote:
> Hi,
>
> I'm pretty sure there is a number of options to achieve this, so I'm
> asking here. I often need to generate small unique tokens (like for
> invitation codes or unimportant authentication token).
>
> In the past I've been using Digest::SHA1.hexdigest(some string) which
> gives us something like "d2b7882fa08bb6de8dca62f16298683bfe4f0738".
> It's not very user friendly though, and definitely not small.

I've mostly just used a substring on SHA1 - hexdigest[8...16] is small
enough to be usable, but still pseudo-random enough for temporary
tokens to not be guessable.

> More recently I've been using ActiveSupport::SecureRandom.base64(6)
> which generates "Xst7JGF6" or "zXxWY/Y/", but sometimes it contains
> non-url friendly characters like "/".

Base64 is A-Za-z0-9/-.  Gsub / for _ and you're pretty url friendly.

> What do you use ? Is there a specific gem to achieve this in a robust
> fashion (= making collisions unlikely, and specify the characters to
> be used, like mixture of numbers and characters for instance ?)

Lastly, not terribly robust, but functional:

  chars = ['A'..'Z', 'a'..'z', '0'..'9'].map{|r|r.to_a}.flatten
  Array.new(6).map{chars[rand(chars.size)]}

--
Jamie