From: Scott Brickner To: Cedric Tefft Subject: Re: 2047 bit keys in PGP Date: Thursday, January 04, 1996 3:41PM

Return-Path: <sjb@universe.digex.net> Message-Id: <199601042141.QAA15905@universe.digex.net> X-Authentication-Warning: universe.digex.net: Host localhost didn't use HELO protocol To: Cedric Tefft <CedricT@bart.datastorm.com> Subject: Re: 2047 bit keys in PGP In-Reply-To: (Your message of Thu, 04 Jan 1996 14:12:00 PST.) <30EC5109@ms-mail.datastorm.com> Date: Thu, 04 Jan 1996 15:41:51 -0600 From: Scott Brickner <sjb@universe.digex.net>

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Cedric Tefft writes:

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If his algorithm effectively cuts my keyspace in half, I need to make it

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twice as large as I would need if my attacker's best algorithm were brute

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force.

Um. No. If his algorithm cuts the keyspace in half, you only need to make it one bit larger.

You are correct. I'm afraid I was thinking one thing and typing another. What I meant to say is that the attacker has an algorithm that effectively cuts my keySIZE (instead of keyspace) in half, i.e. his algorithm requires him to try on average only 2^1023 keys (instead of 2^2047 for a brute force attack) to crack my key of 2048 bits. Thanks for pointing this out. "Who needs encryption when their thoughts are unclear in plaintext?" - Cedric