[16079] in cryptography@c2.net mail archive
RE: "Approximate" hashes
daemon@ATHENA.MIT.EDU (Keith Ray)
Wed Sep 1 15:54:09 2004
X-Original-To: cryptography@metzdowd.com
X-Original-To: cryptography@metzdowd.com
From: "Keith Ray" <keith@nullify.org>
To: <cryptography@metzdowd.com>
Cc: "'Marcel Popescu'" <Marcel_Popescu@microbilt.com>
Date: Wed, 1 Sep 2004 14:27:43 -0500
In-reply-to: <0c4601c49033$caecb9a0$726e9cd9@mark>
> -----Original Message-----
> From: owner-cryptography@metzdowd.com
> [mailto:owner-cryptography@metzdowd.com] On Behalf Of Marcel Popescu
> Sent: Wednesday, September 01, 2004 9:56 AM
> To: cryptography@metzdowd.com
> Subject: "Approximate" hashes
>
> I am trying to build a Windows anti-spam thingy; it's
> supposed to "sit" in
> between the mail client and the outer world, and indicate through mail
> headers whether the incoming mail has a valid hashcash
> http://www.hashcash.org/ "coin" (and, of course, to automatically add
> hashcash to outgoing emails).
>
> My problem is that I don't know what happens with the email in transit
> (this, I believe, is an observation in the hashcash FAQ). I
> am worried that
> some mail server might dislike ASCII characters with the high
> bit set, or
> that a client uses some encoding which for some reason
> doesn't make it to
> the destination unchanged.
>
> Hence my question: is there some "approximate" hash function
> (which I could
> use instead of SHA-1) which can verify that a text hashes
> "very close" to a
> value? So that if I change, say, tabs into spaces, I won't
> get exactly the
> same value, but I would get a "good enough"?
>
> I don't know if this is possible. But if it is, I though this
> would be a
> good place to find out about it.
nilsimsa
Computes nilsimsa codes of messages and compares the codes and finds
clusters of similar messages so as to trash spam.
What's a nilsimsa code?
A nilsimsa code is something like a hash, but unlike hashes, a small change
in the message results in a small change in the nilsimsa code.
http://lexx.shinn.net/cmeclax/nilsimsa.html
--
Keith Ray <keith@nullify.org> -- OpenPGP Key: 0x79269A12
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