1993-02-21 - Trapdoors

Header Data

From: Eric Hughes <hughes@soda.berkeley.edu>
To: cypherpunks@toad.com
Message Hash: 6b2ec4a49ee65fe1631aa1d6563107947df0552b0949c449557264dbae00fbb0
Message ID: <9302212154.AA02012@soda.berkeley.edu>
Reply To: <9302182057.AA00885@tadpole.tadpole.com>
UTC Datetime: 1993-02-21 21:58:03 UTC
Raw Date: Sun, 21 Feb 93 13:58:03 PST

Raw message

From: Eric Hughes <hughes@soda.berkeley.edu>
Date: Sun, 21 Feb 93 13:58:03 PST
To: cypherpunks@toad.com
Subject: Trapdoors
In-Reply-To: <9302182057.AA00885@tadpole.tadpole.com>
Message-ID: <9302212154.AA02012@soda.berkeley.edu>
MIME-Version: 1.0
Content-Type: text/plain


Jim writes:
>Interestingly enough, V9 SPARC has a population count (number of bits
>set in word) instruction that was put in specificly at the request of
>No Such Agency.

Does anybody have a good idea what applications this is useful for?

My first thought is that it's a very quick way to do linear error
detection codes, since this instruction directly computes the Hamming
weight of a code word.

I can also see it being useful to detect correlations between
sequences, such as a trial random stream and a known pseudorandom
number generator.  One would XOR the streams together and then count
bits to calculate a correlation frequency.

Other ideas?

Eric





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