[ntp:questions] Re: hacking NTP autokey with / without IFF

David L. Mills mills at udel.edu
Mon Jan 10 14:02:14 UTC 2005


The means to retrieve the group key from the TA needs to be secure. The 
means adopted in the present scheme is to request the group key as a 
secure PEM exchange, providing the client encryption key as an argument. 
This is done at the ISC site using a secure web form. The form could of 
course be replicated for local use. The group key value is thus obscure 
to anybody that doesn't know the client ecryption key. The data are 
never decrypted by the client; those operations are done by the Autokey 
routines as required.


manel_torralba at mail.com wrote:
> Hi Dave,
> Em... I am dumber than you think, given your advanced answer. I am not
> yet enlightened.
> Basically I am trying to derive some very practical "do´s and don´ts"
> from the IFF Autokey schema. But I don´t really understand it well.
> The texts assume the reader has quite a bit of context....
> The best phrase that comes close in your documentation is this:
> "The TA generates IFF parameters and keys and distributes them by
> secure means to all servers, then removes the group key and
> redistributes these data to dependent clients. Without the group key a
> client cannot masquerade as a legitimate server."
> Say I am setting this up in host S. I run ntp-keygen -T -I and then
> ntp-keygen -e > ntpkey_S_IFF_for_clients. Then I go to the client C and
> run ntp-keygen, and copy over ntpkey_S_IFF_for_clients (from S). I set
> up all the links and init files and I have the following files:
> Server S: ntpkey_cert_S, ntpkey_host_S, ntpkey_IFF_S
> Client C: ntpkey_cert_C, ntpkey_host_C, ntpkey_S_IFF_for_clients
> So If I want to hack the entire community of S´s clients, and
> impersonate S, what files do I need ?
> - Do I need ntpkey_cert_S + ntpkey_host_S + ntpkey_IFF_S ?
> - Do I need ntpkey_host S + ntpkey_IFF_S ?
> - Is ntpkey_IFF_S enough ?
> Thanks,
> Manel T.

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