An It Question (probably To Danny Or Tom)

[Greetings]

Got an exam tomorrow, need to know the correct answer and explanation for the following task:

(excuse me, for my technical english is shit)

The bank has a private ( A ) and public ( B ) key.

John has a private ( P ) and public ( Q ) key.

A certifying organization has a private ( C ) and public ( D ) key.

John wants to send a message to the bank. What will he send and how?

IMO this is how it goes:

John publishes his public key and the certificate which includes his public key to certify that he is the holder of it. He sends the message to the bank, enciphering it with his private key. The bank then de-cyphers his message using his public key.

However there is one problem. This message can be intercepted and viewed by an unauthorized person. Therefore John should encipher the message he is sending with the bank's public key, but then the bank won't know it's John who has sent the message because there is no certificate.

Can one encipher a message twice using your own key to certify that you are who you are, and then encipher it with another key? If not, what's the correct answer?

Edited June 8, 2006 by Inur

[sfboy]

There's a full description of how RSA works at http://ospkibook.sourceforge.net/docs/OSPK...ppendix-pkc.htm

There's a bit on digital signatures at the bottom of

http://www.mathaware.org/Sauerberg_PKC-essay.html

hope that helps

Edited June 8, 2006 by sfboy

[Greetings]

Thanks dude, some useful information there

Cheers!