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security of RSA signatures & authentication

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Karma Crypt
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PostPosted: Sat Dec 07, 2002 2:34 am    Post subject: security of RSA signatures & authentication Reply with quote

Can anyone quantify the security of RSA signatures and authentication?

For example: if you know my public key and you had an authenticated message from me, then how long would it take on a 2 GHz Pentium to establish my private key? And does the time required fall linearly with the number of 2 GHz PC's on the job?

And what if I kept publishing a new public key every week? Do these extra keys make it easier for you to discover my private key? If yes, then is this an exponential or linear increase in "ease of deriving"?

I know that "theoretically" this is a very difficult task, but I would really appreciate some hard figures.

Are there better or more secure authentication algorithms out there now? And could I legally use those on a web site?

Thanks.
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squidly
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PostPosted: Sat Dec 07, 2002 3:44 am    Post subject: Reply with quote

Im not sure of how long it would take on a 2Gig P4 but it would more depends on the length of you key. IE if you have a key that is 40 bits it would not take all that long (perhaps a couple of weeks), if you have a key that is above 80 bytes then you are looking at a brute force of several years. If you are interested in the mechanics of Cryptography I would recomend that you get Applied Cryptography and read that (very good book on the various Cryptographic algorythims out there )

HTH

Squidly
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flw
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PostPosted: Sat Dec 07, 2002 4:18 am    Post subject: Reply with quote

Try searching PKI and private/public key exchange. As well as cryptology.

It's not just a processor power to open private key by brute force. That is only one piece of many required with time to determine the key. In your example you also assume keys are not time stamp sensitive. i.e. private key today is not the private key tomorrow. You could end up chasing the key as it is changing based of the time stamp of each attempted authentication.

Good Luck
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