Don't use word codes for guisers / templars / etc. They're too easily guessable. Instead, use CRYPTO CODES, which cannot be cracked without a lot of computing power!

STEP 1:

Find two very large prime numbers. You can manually do it, or use this site: http://www.numberempire.com/primenumbers.php and select 'Find next' and mash a lot of digits

EXAMPLE PRIMES:

23423784347 and 928746263

(Note: They must be very long, or they won't be secure)

STEP 2:

MULTIPLY those two primes, e.g. on google, you will get a result like: 2.1754752e+19

STEP 3:

Post 2.1754752e+19 in chat, don't reveal the primes

STEP 4:

The next day, reveal your primes: 23423784347 and 928746263. Other people can multiply them and verify that it matches your code.

This is the same mechanic used by modern cryptosystems. It is trivial to verify the product of two primes, but extremely difficult to factorize the product of two primes.