Secure Token URL - How secure is it? Proxy authentication as alternative?

Question

I know it as secure-token URL, maby there is another name out there. But I think you all know it.

Its a teqniuque mostly applied if you want to restrict content delivery

Answer 1

It's called MAC as far as I understand.

I don't understand what's wrong with hashes. Simple calculations show that a SHA-1 hash, 160 bits, gives us very good protection. E.g. if you have a super-duper cloud which does 1 billion billions attempts per second, you need ~3000 billions billions years to brute force it.