Is it possible to check the credentials of the person who signed the document on behalf of a digital signature?

Yes, it is only necessary to look accessible to all users of electronic signature certificate owner. When you receive the keys of electronic digital signature in the employee organization leader confirms the position and powers of the employee (including the right to sign certain categories of documents). On the basis of the certificate of the public key signature indicates the position and powers of the electronic signature of the owner.

9. What if the private key is lost or electronic signature was in the hands of unauthorized persons?
This is called EDS key compromise. The first task in this situation is the early notification Certification Authority about what happened to output from the compromised key actions in the system. Since then, the signature becomes valid and you can rest easy. Then you can begin to address the issue of getting a new certificate of the signature key.

What is encryption?

Encryption - the mathematical science of codes, ciphers and secret messages. Throughout history, people have used encryption to exchange messages, the contents of which, they hoped, would not be able to read no one except the recipients.

Today, there are computers capable of performing encryption for us. Digital encryption technology went beyond the simple secrets. Encryption is used for more complex tasks, such as checking the websites of the individual author's anonymous browsing or using the Tor network.
Under certain conditions, the encryption can be fully automatic and easy to use. But if something goes wrong, it is helpful to understand what was going on. Then you will be better protected from the problems.