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Up: 3.3 Data Security: Cryptography
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Using my private key and the message I am sending, I have my computer
make a particular calculation that results in a piece of information
called a ``digital signature''. Since it involves my private key, the
signature can only have come from me. And since the calculation uses
the message I'm sending, the signature is only for this message. I then
have my computer attach the digital signature to the message, and I
send to you.
When you receive the message, your computer does a calculation that
uses the message, the digital signature and my public key. Since my
public and private keys are related, the calculation can verify 1) that
my private key was used to create the signature and 2) that the message
you received was used to create the signature.