A lot of the time, the randomness used must be secret (for nonces etc.) but your solution is an interesting way to implement a CRS (http://en.wikipedia.org/wiki

A lot of the time, the randomness used must be secret (for nonces etc.) but your solution is an interesting way to implement a CRS (http://en.wikipedia.org/wiki/Common_reference_string_model http://en.wikipedia.org/wiki/Common_reference_string_model) which is very useful in some cryptographic primitives. A CRS is a common string, typically random, that anyone can access, but cannot be controlled by any one party. Another typical thought-implementation of this is using stock market prices -- predict those accurately and you'd do better things with your time than break some crypto protocols.