Subject: Krb5 subsession key negotiation text

From: "Theodore Y. Ts'o" <[email-masked]>
Date: Thu, 12 Nov 1998 00:05:11 GMT

A while back, I promised Cliff I would write a new subsession key
negotiation text for the kerberos-revisions document, so here it is.  My
apologies for this being rather late.

This text replaces the paragraph beginning "One way that an application
may choose to negotiate a key..." in section 3.2.6, "Using the
encryption key" of the kerberos-revisions-01 document:

	One way that an application may choose to negotiate a key to be
	used for subequent integrity and privacy protection is to derive
	it from the ticket session key as follows.  Encode the ctime
	from the authenticator using the ASN.1 DER encoding of
	KerberosTime.  Encrypt this encoding with the ticket session
	key, and use the n-fold primitive to produce an n-bit key, which
	can be used immediately after correcting the key for parity (if
	necessary).  

	The advantage of this scheme is that both sides can
	independently compute the subsession key to be used without
	concern for the quality of the communication partner's random
	key generator.

							- Ted
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