Password from SHA1 to md5

Hi

Firstly apologies if this in the the wrong place please feel free to move and secondly given the nature of the question I’m not expecting a flood of replies!

However, here goes.

I am working on adding my users to phpbb. All is going well until I came to the passwords. As far as I can gleam EE uses SHA1 (although I have seen references to the fact it can use md5) and phpbb uses md5.

I can set the phpbb to ask users to request a new passowrd which is my fall back position as you have to enter the email address you registered with which for many users may be a problem as I have 30k +

Is there a way to either:

1. Convert the passwords to md5 within EE and then export to phpbb; or
2. Recreate the way EE checks the password against its SHA1 hash so that I can add that code to phpbb

Any help or suggestions appreciated - but please try and keep them simple as password encyption, hashing and salting is not my field.

Thanks Mark

PS - I am using EE 1.7.1 and phpbb 3.0.10