zeb

07-09-2005, 11:52 PM

Hi,

I wonder if you have different tokens with different keys, token A

and token B given the same challenge will create the cipher texts CA

and CB respectively. Even though the cipher texts differ they may still

give the same response if CA mod 10^8 = CB mod 10^8.The token is a 56

bit DES-key and the input is 8 digits sending from a webserver and the

output is 8 digits

If an attacker even with infinite computer power cannot decide the key

of the token given just one challenge-response pair. How is it possible

to count how many challenge – response pairs are needed to be able with

great probability to decide the key of a token for an attacker with

infinite computer power?

Ok Before you have one challenge-response pair I suppouse that there

are 2 ^56 keys in the token and the when you have one challenge

-response pair you had used 10^8 keys = 2^27 and of the truncated

value you have used 2^8 and the if you want to count a new challenge

-response pair how should I continue

Please send me some information how to solve this

Your regards Tomas

--

zeb

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I wonder if you have different tokens with different keys, token A

and token B given the same challenge will create the cipher texts CA

and CB respectively. Even though the cipher texts differ they may still

give the same response if CA mod 10^8 = CB mod 10^8.The token is a 56

bit DES-key and the input is 8 digits sending from a webserver and the

output is 8 digits

If an attacker even with infinite computer power cannot decide the key

of the token given just one challenge-response pair. How is it possible

to count how many challenge – response pairs are needed to be able with

great probability to decide the key of a token for an attacker with

infinite computer power?

Ok Before you have one challenge-response pair I suppouse that there

are 2 ^56 keys in the token and the when you have one challenge

-response pair you had used 10^8 keys = 2^27 and of the truncated

value you have used 2^8 and the if you want to count a new challenge

-response pair how should I continue

Please send me some information how to solve this

Your regards Tomas

--

zeb

------------------------------------------------------------------------

Posted via http://www.webservertalk.com

------------------------------------------------------------------------

View this thread: http://www.webservertalk.com/message1069097.html