[freehaven-dev] Brief notation explanation on Anon network email

[Michael J Freedman <mfreed@MIT.EDU>]

>ROUTE_CREATE_PACKET
>
>Routing Information Header
>
>[K_s_1, K_d_1 {K_s_2, K_d_2 (K_M, K_d_2, K_d_1, K_A)_PK_M}_PK_2]_PK_1
>
>Message 
>
>      [{(MSG)_K_M}_K_s_2]_K_s_1
>
>
>Packet:   {routing info} o {message}

Just to clear up any confusion that might exist with notation, this
describes some "onion encryption" packet.  That is, 

	(K_M, K_d_2, K_d_1, K_A)_{PK_M}

is the message block (K_M, K_{d_2}, K_{d_1}, K_A) encrypted under PK_M.
Therefore, other possible notation for the above formula is the following:

PACKET-M =	E_{PK_M} ( K_M, K_{d_2}, K_{d_1}, K_A)
PACKET-2 = 	E_{PK_2} ( K_{s_2}, K_{d_2}, PACKET-M)
PACKET-1 = 	E_{PK_1} ( K_{s_1}, K_{d_1}, PACKET-2)

Alice sends PACKET-1 to 1

Hope that is clearer.  It's the fairly standard onion-encryption idea of
many "mix-nets".  Sorry for the formatting problems with my previous email
and any unclear language (such as "protectation from reply" --> "protection
from replay attacks", and such ilk.)  

Enjoy!
--mike





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"Not all those who wander are lost."                  mfreed@mit.edu