3 ms·
Ah, so if I understand correctly, you could detect message eavesdropping as follows: 1. We agree ahead of time to always observe the first digit of magic paper
by ythn 9y ago
Ah, so if I understand correctly, you could detect message eavesdropping as follows:
1. We agree ahead of time to always observe the first digit of magic papers first.
2. I send you a message that includes eavesdropping-detecting magic pieces of paper
3. We then compare what you measured as first digits to what I measured as first digits
4. If the digits do not match, it means someone eavesdropped on the magic pieces of paper I sent and observed the wrong digits first.
But then aren't we back to the same secret distribution problem, where the secret is which digit we should observe first on magic papers?
- im3w1l 9y agoAs you point out, that protocol is flawed. Here is a protocol that works (BB84): Needed: * A way for Alice to communicate (classically) with Bob that can be read by Eve, but CANNOT be manipulated by Eve. * A way for Alice to send magic paper (qubits) to Bob, that CAN be intercepted and manpulated by Eve. Steps: 1. Alice sends a bunch of magic paper to Bob. 1.5 Eve potentially intercepts the shipment and manipulates it. 2. For every piece of paper, Alice randomly decides which digit to check. Bob does the same independently. 3. Alice and Bob tell each other over the classic channel, that Eve cannot intercept, which digits they checked. 4. They discard the papers where they checked different digits, and use the rest to form a One Time Pad.