> In consensus systems, however, any difference in behaviour can be a fatal vulnerability. Another issue can come if you have code like this, and different va

> In consensus systems, however, any difference in behaviour can be a fatal vulnerability. Another issue can come if you have code like this, and different validations are used. if (signature_valid()) { // Safe because we already verified signature. use_signed_message_or_die(); } In practice the check and usage could be very far apart in the code (maybe using the type system to keep track of verified signatures), or even in different programs.