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← 06-08 The First Hop Solution

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Showing Revision 1 created 06/29/2012 by Amara Bot.

  1. The third one is the correct answer.
  2. The first one wouldn't work. R2 couldn't decrypt this message
  3. and wouldn't know where to send the next hop.
  4. This one would work for the first hop. R2 would decrypt it.
  5. Note to send it on to R5, but would then when R5 receives it,
  6. it wouldn't be able to decrypt this message and know where to send it.
  7. It's also unnecessary to have this extra decryption using KUR2.
  8. This outer method has already encrypted using that public key.
  9. Anyone who can decrypt this message can also decrypt that one,
  10. so there's no value added by having this encryption.
  11. The third one is the best answer.
  12. Here we sending the message encrypted using R2's public key, so R2 can decrypt it.
  13. It has the next routing hop in plaintext in the message that R2 can decrypt.
  14. Then it has the rest of it encrypted using R5's public key,
  15. so R5 will be able to decrypt the next hop and learn that that should be sent on to R4.
  16. The problem with the fourth choice--it would work for this hop,
  17. but then when R5 decrypts it, it wouldn't know what the next hop is.
  18. The final option wouldn't work, because R2 would get the message to send to R5
  19. and send the message here--which is M4.
  20. That's encrypted using R4's public key. R5 wouldn't know where to send the message.
  21. The only one that works is the third choice.
  22. In general, for onion routing to work, we need each message in the chain to be the message
  23. that's sent to the router Rik.
  24. It's going to be a message encrypted with that router's public key.
  25. It will have as its contents something explaining the next destination
  26. as well as the message that should go to that next destination.
  27. We can wrap as many layers as we want.
  28. The more layers there are, the more hops we go through,
  29. the less risk there is that all of the links in the chain can collude
  30. or that a party can observe all of the communication and learn what's being communicated.