Digital signature is the equivalent of a handwritten signature. It is used to sign electronic documents, that is, to confirm the authenticity of these documents. In fact, it is an encrypted electronic stamp that confirms the authenticity of information, such as emails and other electronic documents. The digital signature confirms that the information originates from the author of the signature and has not been modified.
In other words, digital signature guarantees the authenticity of certain information transmitted digitally.
Beware - there is a difference between digital signature and electronic signature. The term digital signature is used in the USA and Asia rather than in Europe where, from the EU’s initiative, the concept of electronic signature came into use. In general, however, the concept of electronic signature is a broader term. It may refer to a signature in electronic or digital form that can be nothing more than a mere symbol or image of a traditional handwritten signature, which cannot guarantee any of the above mentioned characteristics of a digital signature.
What is a digital signature used for?
Digital signature is a solution to prove authenticity of documents in an impersonal contact. It is typically used to sign an email or a document (e.g. a contract in PDF). However, this is not the only use. Digital signature can be used as a proof of credibility, authenticity and to verify the identity of a person as well as to confirm the status of a document, a particular report or transaction.
Although a digital signature can be used to encrypt an email, we cannot assume that everything that is digitally signed is encrypted and cannot be read by a third party. This is because the digital signature ensures the authenticity and not the security of the document - a document being transmitted is not as such protected from unauthorized access, it is only a guarantee that information originates from the sender or from the author and that the content of the document or message has not been modified by a third party on the way between the sender and the receivers.
What is the legal value of a digital signature?
In most developed countries, a digital signature has the same legal value as a classic signature.
How is a reliability of a digital signature ensured?
In the digital world, almost anything can be falsified, including a signature. Anyone could add any digital signature to any document and it would be very difficult to prove such a fraud. That is why there was a need to find a way to ensure the digital credibility of such signatures. This is how the so-called certificate authorities have been established. Their role is to issue digital certificates such as digital signatures. In order to do so, they first verify your identity. A certificate (digital signature) issued by a certification authority becomes a so-called qualified certificate that has the exact same value as a conventional handwritten authenticated signature.
How does the digital signature work?
Encrypted credibility of a digital signature is the foundation principle. A certificate that proves your identity is therefore needed. So if you are sending a signed document or an email, you also need to send your certificate and the public key allowing decryption that will be used by the other party (receiver), which must be able to verify the authenticity of your document or signature. If the signer sent or shared his or her private encryption key, the other party could easily fake your digital signature. For this reason, the so-called asymmetric cryptography is used - the author uses the so-called private key and everyone else has the so-called public key (which, as the name implies, is publicly available). The public key enables to verify the signature, but does not allow digital signature creation.