Re: recompressing the deflate streams in a PDF

On Mar 27, 6:02 pm, byaa...@xxxxxxxxx wrote:

Finally, just out of curiosity, just how exactly are the signatures
generated? Are they closed (unknown) algorithms? Or do they rely on
some sort of shared key?

http://en.wikipedia.org/wiki/Public_key_cryptography
http://en.wikipedia.org/wiki/Digital_signature

First, public key cryptography involves an algorithm that uses two
keys: one for encrypting and another for decrypting. The algorithm is
sufficiently complex that it is infeasible to compute the decryption
key even if when the encryption key is known (and vice versa).

When PKC is used, I can publish my public key and keep my private key
to myself. If you want to send me something securely, then you encrypt
it using my public key; only I can decrypt it.

Digital signatures adapt this idea somewhat. Instead of encrypting the
whole document using a public key, I encrypt a *hash* of the document
I'm signing using my *private* key. The encrypted hash forms my
signature. Anybody can then *decrypt* the signature using my public
key, and know that *only* I could have created the signature because
*only* I have my private key.

.

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