reCAPTCHA Keys - length and character set

[i-imagine]

I have released a plugin for Coppermine Photo Gallery that uses the
recaptcha_get_signup_url function. Users enter the keys into the app's
database (sql) after signing up with reCAPTCHA through a window
integrated into the plugin.

For the next revision I would like to do some string checking on the
keys (for the user's and db's sake).

1) How many characters are in (or expected to be in) each key? Is
there a min/max that I should expect?

2) What is the character set limited to? Any specials characters? Any
changes expected in the near future?

Apologies if the answer is elsewhere and I have not found it. This is
not a "rush request" at all.

Thanks in advance for your time and reply.
Joe Carver

Links:
Coppermine Plugin page
http://forum.coppermine-gallery.net/index.php/topic,60626.0.html

Coppermine Photo Gallery Main Page
http://coppermine-gallery.net/

reCAPTCHA in Coppermine (my own pages)
http://www.i-imagine.net/
http://www.gallery.josephcarver.com/natural/

[reCAPTCHA Support]

Hi,

The string can be of any length or set of characters. We recommend that you test that the user can actually see the CAPTCHA, since this is the best check for a valid key.

- Ben

--
reCAPTCHA: stop spam, read books
http://recaptcha.net

[i-imagine]

Thanks!