Subject: [AVT] Size of SRTCP authentication tag of AES_CM_128_HMAC_SHA1_32 cipher suite

From: "Wyss, Felix" <[email-masked]>
Date: Sun, 9 Sep 2007 01:08:34 -0400

RFC#4568 is ambiguous regarding the size of the SRTCP authentication tag
for the AES_CM_128_HMAC_SHA1_32 cipher suite.  The table in section 6.2
indicates that it should be 80, but section 6.2.2 states: "This
crypto-suite is identical to AES_CM_128_HMAC_SHA1_80 except that the
authentication tag is 32 bits."  I did not see anything in RFC#3711 that
would indicate that weak authentication tags are not valid for SRTCP --
hence the ambiguity.  

Is there consensus on whether the SRTCP authentication tag must always
be 80 or whether the table in section 6.2 is in error?  

Thanks,

Felix I. Wyss

Interactive Intelligence, Inc.

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Audio/Video Transport Working Group
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From: "Robert R. Gilman" <[email-masked]>
Date: Sun, 09 Sep 2007 14:19:04 -0600

Take a look at Section 5.2 of RFC 3711.
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Bob Gilman       [email-masked]      +1 303 538 3868

Wyss, Felix wrote:
> indicates that it should be 80, but section 6.2.2 states: “This 
> authentication tag is 32 bits.”  I did not see anything in RFC#3711 that 
> ------------------------------------------------------------------------
>