about uncovering skype

[江晓林 <linjiangxiao () gmail com>]

HI:
    i have recently read the paper <Skype uncovered>,and have some
questions.In the part of UDP packet deciphering,the writer had mentioned
that "The RC4 key is generated using src/dst IP plus packet ID",and in the
figure the writer showed that we could use the src/dst IP plus packet ID to
generate the crc32,but in the former page,there had alread been a
crc32,so,where did it come from,and how should do to generate the correct
crc32. Besides, for the src ip,if the client was behind a NAT,its src ip
would be modified by the router when the packet pass out the NAT,and the
receiver would see another src ip,so how could it generate the right rc4
key?
   Finally,can somebody show me the deciphered data of the example,i wonde
if mine is right or wrong.

expecting for your reply.

Sincerely,
Jiangxiao

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