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Re: [ntpwg] Parsing NTP packets regarding MACs and EXTs.

Hal Murray <hmurray@megapathdsl.net> Tue, 21 June 2016 09:40 UTC

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To: Harlan Stenn <stenn@ntp.org>
From: Hal Murray <hmurray@megapathdsl.net>
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Subject: Re: [ntpwg] Parsing NTP packets regarding MACs and EXTs.
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stenn@ntp.org said:
>> 2. A MAC field is 20 bytes or less.
> We have a recollection that this has sometimes been larger, but we haven't
> gone thru some of the older code to see when this might have changed.  I
> know we intended to support longer MACs.

What do you mean by "MAC field"?

The simple shared key MACs include a 4 byte header.  MD5 mode has a 16 byte 
hash for 20 bytes total.  SHA1 has a 20 byte hash for a 24 byte total.


stenn@ntp.org said:
> A legacy MAC is well-formed.  We know where it's coming from.  We know what
> keyID we're expecting from that source. 

I don't understand what you mean by "know where it's coming from".  The 
server doesn't know which clients will be using which keys.


-- 
These are my opinions.  I hate spam.



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