Are there predictable, yet secure hashes?
It sounds to me like you want to is produce a hash that proves integrity, and can be authenticated with some key pair. 

In that case, I would release a HMAC using a RSA public key and your statement along with the RSA signature of the aforementioned HMAC.

That way someone could verify the integrity and authenticity of your statement while only knowing your RSA public key and the signed HMAC.