Newbie questions: What is OTP? What about probabilistic encryption vs quantum cryptography?
OTP is one-time pad. There was an article on quantum cryptography in the October '92 Scientific American. For probabilistic encryption, I think the sci.crypt FAQ has a reference.
How do they give one 100% certainty that they can't be broken?
OTP and some flavors of probabilistic encryption are information- theoretically secure. For OTP, this is obvious if you think about it a bit. Quantum cryptography relies on the math of quantum mechanics, whose validity is ultimately empirical but rather well tested.
100% objective certainty of the scheme's invulnerability.
My point is, invulnerability to *what attack*? An attacker may know the algorithm, or not; may have known plaintext; may be able to choose plaintext; may be able to read a channel, or to garble it, or to change it; may have limited or unlimited space and time; might be able to factor in polynomial time -- there are a lot of parameters here. And it makes no sense at all to say, "Well, let's just consider the strongest possible attack." Eli