[tcpm] "The SYN trick"

[Eric Rescorla <[e-mail]>]

I'd suggested using the ISNs as an implicit diversifier for
a single master shared key.

E.g.,

K_connection = HMAC(K_master, ISN_i, ISN_r)

As Joe points out if you use ISNs as an implicit diversifier
for a shared connection key. Obviously, you can't use the 
ISN sound in the SYN/ACK to key the initial SYN. The natural
thing to do here is:

- For the initial SYN use K_connection = HMAC(K_master, ISN_i, 0)
- For subsequent packets use K_connection = HMAC(K_master, ISN_i, ISN_r)

-Ekr

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