Encryption with certificate security

This type of encryption is the most secure way of protecting your PDF documents as each document is encrypted for one or more recipients and only these are able to open such documents. Furthermore, the author of the document also has the option of deciding whether the file may be read, printed, processed, added to or copied.
With encryption with certification an asymmetric method is applied. This means that it is only possible to encrypt and decrypt with two different keys: a private and a public key.
A digital certificate serves to verify, beyond doubt, the identity of its owner
What does all this mean in practice?

Let us take the example of Alice and Bob again: Alice wants to send Bob an up-to-date financial statement in PDF format by e-mail, to do this she uses simple password protection

There is now, however, a third person in the equation, Carl. Carl is not only a troublemaker, but was also hired by a competitor of Alice and Bob to obtain information on the liquidity of the company, 'Alice & Bob Ltd.'. As he is an IT expert, he is able to intercept the e-mail with the encrypted PDF attachment from Alice and, using crack software which can be relatively easily downloaded from the Internet, Carl removes the password for opening the file and forwards the decrypted document to his employer.

What can be done?

Alice can do very little to prevent Carl intercepting the file sent via e-mail. Therefore, she must ensure that Carl is unable to crack the encryption and open the document. This is where certificate security comes in.

Alice and Bob each obtain a certificate (Where from? Find out more here.) and both install these on their computers. Each certificate contains the name of the owner, the name of the issuer, a serial number and the duration of validity and, of course, the necessary key pair: the private and the public key.

Alice now encrypts her document with Bob’s public key which she received from him beforehand. Only Bob’s private key is able to decrypt the document. To allow Bob to also send confidential information to Alice via e-mail, he also receives the public key from her. He is therefore now in a position to process the document and encrypt it with her public key, Alice is thus the only person who is able to reopen the amended document … all of which leaves Carl in the dark!

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