Subject: Cross certification message protection (RFC2510)

From: [email-masked]
Date: Fri, 19 Mar 1999 21:13:07 GMT

In RFC 2510 in section 4.6.1 it clearly states that a MAC based on an
authentication code
should be used for the message authentication and integrity.

In Appendix B section B7 it states that the protectionAlg should be set to
MSG_SIG_ALG.
This does not seem consistent.  I am assuming that B7 really meant to say
MSG_MAC_ALG,
if this is not the case I have a ton of other questions ...

                              Mike

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From: Juergen Walter <[email-masked]>
Date: Mon, 22 Mar 1999 16:56:47 +0100

Mike,

I beg to differ. MAC based authentication is vulnerable when off-line
guessing attacks are possible (for details see my previous posting on
"Re: New CMC Draft available" that contains comments on CMP). 

Out-of-band methods seems to be quite reasonable. Nevertheless
authentication via digital signature may be reasonable as well.

Authentication based on HMAC where the plaintext (= input for HMAC
without secret key) AND the ciphertext (= output for HMAC) is contained
in the protocol message needs additional security measures. Encryption
of the message may one of suitable measure (but not the best).
Encryption of the protocol message is allowed in CMP but it is still
recommended to send CMP messages without encryption when I have
understood correctly. Other certificate issuance protocols are
well-known and provide more security but they are not supported by CMP.

You have found an ambiguity in the CMP-RFC. Any other interpretations?

Furthermore message authentication methods are well-known. Attacks and
threats are well-recognized. Why should a further review of CMC and CMP
not profit from this knowledge?

Juergen  

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