I guess it's worth mentioning that people are currently working on removing the Google services dependency in Signal:
https://github.com/WhisperSystems/Signal-Android/pull/5962
18 karma · joined August 25, 2012
The external link list gives nice examples for symbols in different countries.
For instance MD5 collisions are really easy to create but for preimage attacks on MD5 there is still no better approach than just doing brute force.