DNS TXT field usage ?

Mon Mar 29 19:06:08 UTC 2010

Hi Jul

Dkim , SPF ,and Domainkey are sender authentication methods for email system. Which use Public Key Cryptography.

The mail server apends signiture to every outgoing message using private key. the recepient mail server to verify needs the public key which placed in the sender DNS server.  

see

dig suin.edu.sd txt --> for SPF

dig _domainkey.suin.edu.sd txt  --> for DKIM

regards,
-- 
Tarig Y. Adam
Chief Technology Officer
Sudanese Universities' Information Network (SUIN)
T: +249925659149
w: www.suin.edu.sd

> Date: Sun, 28 Mar 2010 14:04:39 +0200
> From: jul_bsd at yahoo.fr
> To: nanog at nanog.org
> Subject: DNS TXT field usage ?
> 
> Hello,
> 
> While watching some parked domains, I recently observed one which has a
> TXT field containing some crypto value, something like a ssh key/RSA 512
> or 1024 output (only the crypto part 'cvxvcvcxvcxv=' ).
> 
> For now, I have referenced the following usage of TXT
> - DNS Server information/version
> - SPF (format like "v=spf1 a mx -all") [1]
> - DKIM (format like "k=rsa\; t=y\; p=MIGfMA0GCSqGSIb3 [...]
> YA+OwSMWQIDAQAB", but always in _domainkey.<domain>) [2]
> - not DNSSec as I supposed first (only DNSKEY, RR, RSIG, NSEC, not TXT)
> 
> Does someone know at what kind of usage this kind of value could
> correspond ? (even if, nearly everything is possible)
> 
> Maybe somebody knows of a webpage referencing common usage of DNS fields ?
> I found http://www.iana.org/assignments/dns-parameters but it points
> only on RFC not practical usage.
> 
> 
> Thanks a lot.
> Best regards,
> 
> Jul
> 
> 
> [1] http://en.wikipedia.org/wiki/Sender_Policy_Framework
> [2] http://www.ietf.org/rfc/rfc4871.txt (7.4)
> 
> Note: current RFC referencing TXT field is
> http://www.ietf.org/rfc/rfc1035.txt
> "TXT RRs are used to hold descriptive text."
> 

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