Le jeu 21/11/2002 à 23:12, John Goerzen a écrit : > After verifying the signature on the data, the receiver does some sanity > checks. One of the checks is doing an md5sum over the entire file > (remember, this includes both the headers and the payload). If it > has seen the same md5sum in the last 60 days, it rejects the request. If > the date of the request was more than 30 days ago, it rejects the request. > > Therefore, the sender is able to reissue the "halt" command legitimately as > often as he/she wants, since the random bits & time will ensure different > md5sums on the recipient. But replay attacks will be useless since the > recipient will have seen the request already, and will reject it. What if the attacker can intercept the messages ? He can prevent a message from being sent, and keep it for another day. Seeing your computer doesn't halt, you resend the message, and the attacker has 30 days to use what he has stolen. A secure way to handle this would be a challenge/response authentification, or a system similar to SSH's one-time passwords. -- .''`. Josselin Mouette /\./\ : :' : josselin.mouette@ens-lyon.org `. `' joss@debian.org `- Debian GNU/Linux -- The power of freedom
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