[Wolves] so hows this signed messege work then?

[Simon Morris]

On 28/09/05, roundyz <roundyz at hotpop.com> wrote:
> as subject?
> I make a key i gathered that much.
> The key was for encryption. it works for that.
>
> Hows it work for signing the message,
> I know I don't need a key to open Ron's messages. So would that work with
> mine?
>

Hmmm, how long do you have? Assuming you know that cryptography relies
on a pair of numeric keys and that data encrypted by key A can only be
decrypted by key B* _and_very_importantly_ visa versa.. data encrypted
by key B can be decrypted by key A

Your message is taken and hashed. That is the message is represented
by a hash, and that hash can only represent that message. If you
changed the message and rehashed it you would get a different hash
digest.

Ron then takes his private key and encrypts that hash with it. You
receive the message and also hash the message using the same
algorithm.

So you now have your own hash of his message and Rons encrypted hash
of the message. You can decrypt Rons version using his available
Public key (you need his key to do this, or you need to use a
keyserver)

Once you've decrypted Rons version of the hash you compare it with yours.

If they match you can know the following:

- Only Ron could have sent the message. Only he has his private key
and you are able to decrypt the hash with his public key successfull
(You DO trust his public key, right? :)

- The message cannot have changed since he sent it. Otherwise the hash
digest would not match with your version.

Easy eh?

* Of course nothing can be guaranteed here. Data might decrypted by a
different key but it is infinitely easier to *find* key B using brute
force key guessing rather than trying. Key guessing still takes an
incredibly long time. Longer than the history of the universe blah
blah blah

--
~sm
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