Subject: I-D ACTION:draft-ietf-pppext-mschapv1-keys-00.txt

From: [email-masked]
Date: Wed, 23 Sep 1998 10:42:18 -0400

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 V1 Credentials
	Author(s)	: G. Zorn
	Filename	: draft-ietf-pppext-mschapv1-keys-00.txt
	Pages		: 7
	Date		: 22-Sep-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.
 
The  Microsoft Challenge-Handshake Authentication Protocol (MS-CHAP) [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  represent-
ing  PPP  packets  in  an  encrypted  form.   MPPE  uses the RSA RC4 [5]
algorithm to provide data confidentiality.  The length  of  the  session
key  to  be  used  for initializing encryption tables can be negotiated.
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 credentials.  The algorithm used to  change  ses-
sion keys during a session is described in [4].

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