On 2010-12-05 6:50 AM, [email protected] wrote:
Hey I don't know what it's called, but I'm wondering how one binds a
challenge/response (or whatever you authenticate with) inside a secure
tunnel to prevent the peer from relaying it on to another party to
answer.
>
I assume it could be as simple as signing a nonce and some parameter
of the channel (such as an ephemeral key) and sending that (or something
derived from it) as the challenge, but curious what the options and
tradeoffs are.
Assume we have a username and password, or equivalently, a question and
a secret answer. Perhaps members of the in group use words in a certain
way that an outsider would not, a shibboleth.
We don't want the attacker to be able to be able to do man in the middle
*AND* we don't want the attacker to mount an offline dictionary attack.
Dictionary attack is not a problem if we have a long obscure
authentication such as
Auth code?
V+C6jtCt7aHf2zi1T3RLpC1ScniWAmxlnci4lrGM
But it is a problem if our authentication is
Who sent you?
Fred
SRP (Secure Remote Password protocol) solves the problem
http://srp.stanford.edu/
copy their source code: You are less likely to screw up.
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