Is there any better indication of how far our freedoms have eroded than the frequency and vigour with which security experts question the means and motivation behind US government actions purportedly intended to keep us safe? Suspicion of the US government has always been natural, of course, but today it has become - quite rightfully - a defence mechanism of the first order.

Our latest example comes from the field of cryptography: Security consultant Bruce Schneier, leaning on analyses from other experts, last week questioned why one of four government-sanctioned random-number generators - the one "three orders of magnitude slower than its peers" - includes what "can only be described as a back door".

In addition to the vulnerability, which Schneier says would be enough to spook cryptographers, there is this to know about the suspect random-number generator: It's one of the chosen four only because the National Security Agency insisted.

The back door boils down to a question of who, if anyone, possesses a "secret set of numbers that can act as a kind of skeleton key," according to Schneier:

"Of course, we have no way of knowing whether the NSA knows the secret numbers that break Dual_EC-DRBG. We have no way of knowing whether an NSA employee working on his own came up with the constants - and has the secret numbers. ... Maybe nobody does. ... We only know that whoever came up with them could have the key to this back door. And we know there's no way for NIST - or anyone else - to prove otherwise."

Which brings us back to distrust: Who at this point is willing to grant the US government the benefit of the doubt? You don't have to be a conspiracy theorist to be worried