Re: Black Eye for NSA, NIST, and Denning

[Derek Atkins <warlord@MIT.EDU>]

The format of the LEAF block is public knowledge.  Here is how it
is formed:


      [80-bit Session key Ks]   [16-bit # ]   [32-bit chip ID]

      [80-bit Unit Key    Ku]

      [80-bit.  {Ks}Ku      ]   [16b {#}Ks]   [32-bit chip ID]

      [128-bit LEAF:  {{Ks}Ku {#}Ks ID}Kf  (Kf == family key)]

Whether or not known plaintext will work is unclear, since you cannot
get {#}Ks (you really don't know what it is outside the chip) and you
also don't know what # is (it is, according to the NSA, a fixed number
in all the chips).

Hope this helps.

-derek

         Derek Atkins, SB '93 MIT EE, G MIT Media Laboratory
       Member, MIT Student Information Processing Board (SIPB)
    Home page: http://www.mit.edu:8001/people/warlord/home_page.html
       warlord@MIT.EDU    PP-ASEL     N1NWH    PGP key available