RE: I-D ACTION:draft-ietf-smime-rcek-01.txt

[Mike Just <[e-mail]>]

Hi Stephen, Sean,

Possibly another item worth including in the Security Considerations
section. Suppose MSG1 is sent to a set S1 of users. In the case where MSG2
is sent to only a subset of users in S1, all users from S1 will still be
able to decrypt MSG2 (since MSG2.KEK is computed only from MSG1.CEK).  I
don't think you intended for your solution to be used for such dynamic
recipient sets, but it might be worth explicitly mentioning this unfortunate
side-effect of key re-use in any case. (Might be enough to mention that the
recipient lists must be the same for each message.)

Mike J.  

> -----Original Message-----
> From: [e-mail] [mailto:[e-mail]]
> Sent: Friday, February 09, 2001 7:27 AM
> Cc: [e-mail]
> Subject: I-D ACTION:draft-ietf-smime-rcek-01.txt
> 
> 
> A New Internet-Draft is available from the on-line 
> Internet-Drafts directories.
> This draft is a work item of the S/MIME Mail Security Working 
> Group of the IETF.
> 
> 	Title		: Reuse of CMS Content Encryption Keys
> 	Author(s)	: S. Farrell, S. Turner
> 	Filename	: draft-ietf-smime-rcek-01.txt
> 	Pages		: 7
> 	Date		: 08-Feb-01
> 	
> This note describes a way to include a key identifier in a CMS
> enveloped data structure, so that the content encryption key can be
> re-used for further enveloped data packets.
> 
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