Subject: I-D ACTION:draft-matsuura-sign-mode-00.txt

From: [email-masked]
Date: Sun, 11 Apr 1999 14:19:44 -0400

A New Internet-Draft is available from the on-line Internet-Drafts
directories.

	Title           : A revised signature mode for the Internet Key
			  Exchange
	Author(s)	: K. Matsuura, H. Imai
	Filename	: draft-matsuura-sign-mode-00.txt
	Pages		: 7
	Date		: 07-Apr-99
	
The Internet Key Exchange (IKE) [HC98] uses the Oakley Key Exchange
Protocol in conjunction with ISAKMP to obtain authenticated and
secret keying materials. Phase 1 of the IKE has several modes with
different number of message passes. For those who are vulnerable to
Denial-of-Service (DoS) attacks and want to save their resource,
three-pass Aggressive Mode is a good choice since it has minimal
number of message passes in Phase 1.

The public-key primitive method in Aggressive Mode provides
significant security advantages over the other alternatives and
should be the method of choice in many implementations.  In the
public-key primitive method, unfortunately, the responder must pay
computational cost as expensive as modular exponentiation BEFORE he
becomes sure that the protocol initiator is really a correct entity.
This can be abused by malicious initiators for a DoS attack; they may
launch quite a large number of bogus requests to exhaust the
computational resource of the responders who verify each request
honestly. The purpose of this document is to solve this problem in
digital-signature method by using a DoS-protection strategy called
falling-together (FT) mechanism [MI98], [MI99]; in the resolution,
malicious initiators or DoS attackers fear their own resource
exhaustion when they want to exhaust the resource of the responder.

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