Subject: I-D ACTION:draft-ietf-pppext-mschapv2-keys-02.txt

From: [email-masked]
Date: Tue, 17 Nov 1998 12:01:33 -0500

A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the Point-to-Point Protocol Extensions Working Group 
of the IETF.

	Title		: Deriving MPPE Keys From MS-CHAP V2 Credentials
	Author(s)	: G. Zorn
	Filename	: draft-ietf-pppext-mschapv2-keys-02.txt
	Pages		: 10
	Date		: 16-Nov-98
	
The  Point-to-Point  Protocol  (PPP)  [1] provides a standard method for
transporting multi-protocol datagrams over point-to-point links.
 
The PPP Compression Control Protocol [2] provides a method to  negotiate
and utilize compression protocols over PPP encapsulated links.
 
Version  2  of the Microsoft Challenge-Handshake Authentication Protocol
(MS-CHAP-2) [3] is a Microsoft-proprietary PPP authentication  protocol,
providing  the  functionality  to  which  LAN-based users are accustomed
while integrating the encryption and hashing algorithms used on  Windows
networks.

Microsoft   Point   to  Point  Encryption  (MPPE)  [4]  is  a  means  of
representing PPP packets in an encrypted form.  MPPE uses  the  RSA  RC4
[5]  algorithm  to provide data confidentiality.  The length of the ses-
sion key to be used for initializing encryption tables  can  be  negoti-
ated.   MPPE  currently  supports 40-bit and 128-bit session keys.  MPPE
session keys are changed frequently; the exact  frequency  depends  upon
the  options  negotiated,  but  may be every packet.  MPPE is negotiated
within option 18 [6] in the Compression Control Protocol.
 
This document describes the method used to derive the initial MPPE  ses-
sion keys from MS-CHAP-2 credentials.  The algorithm used to change ses-
sion keys during a session is described in [4].

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