[tor-dev] Removing Onion Skins

Frank Young pfcodes at gmail.com
Sun Apr 21 15:19:38 UTC 2013

   After circuit extension to the second Node, I realized that the OR
at the second node can decrypt my cells  and successfully process my
circuit extension request to increase my circuit length to three but i
can't decrypt the response from the same OR.
    At first I  thought maybe I was messing up the key for backward
encryption (should be decryption but it is counter mode crypto) but i
realized it wasn't true. I extracted both the KF and KB at the same
time and the crypto scheme is also the same for encryption and
decryption since it is a counter mode AES operation.
    From the tor protocol specification, I will have to remove all
skins starting with the immediate OR towards the exit Node. When the
application of the above specification failed to decrypt the cell
successfully, i decided to remove the skins in reverse order but this
also failed.
   I'm really confused at the moment. Aren't each successive AES
counter operation independent of the previous?

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