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I am trying to understand how md5 authentication works between this 2 cisco routers. The password is cisco in both routers. In the output in the field Auth Data: the hash is different in every packet. Is this the result of a salt? Whats the reason of the field auth crypto sequence number? Does each router has a counter and after initial synchronization both routers increase this counter?

Cisco allows only for max 8 character password so perhaps is using some 'other' algorithm. It is stated that the algorithm is md5 when you issue the command. After some quick queries in some online cracking websites (with rainbow tables) i was not able to reverse the hash. Is this some security by obscurity ?

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Is this the result of a salt?

That's part of it, but the PRNG (link) is also part of the reason why you're seeing different values on there.

After some quick queries in some online cracking websites (with rainbow tables) i was not able to reverse the hash

You better not be able to. Cryptographic techniques like salting should defeat rainbow table attacks on the hashes.

  • While all things in the universe are ultimately mathematical, I'm not sure it's the best descriptor for salting. – Falcon Momot Nov 23 '13 at 9:45
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    Right, I was referring more to the PRNG of the salt, but yes it's indirect and I've probably got to stop adding adjectives at 2am. Added the wiki link to show it's more about a random number added in. Although pepper could also be used both of which are to discerned from padding. – stackuser Nov 23 '13 at 15:32

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