Digital signature and how it works

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Starting with small businesses and ending with public authorities, modern information and computer technologies are introduced in all spheres of life. Therefore, the questions of implementation of electronic document management system that has mechanisms of protection of transmitted documents on the basis of control over document authenticity and correctness are actual. At the same time, during the transition to electronic document flow there is an important issue of both document authorship and the issue of its reliability and protection against alterations. For this purpose a digital signature is used. If for legal entities it is an indispensable instrument which allows to establish an effective document management inside the company and with external contractors, then for individuals it is the way to speed up and simplify the interaction with the government agencies, employers, etc. It is a wrong opinion that digital signature serves for a document encryption. Its main function is to check who sent the document.

A digital signature allows you to prevent security breaches such as:

authentication: a digital signature gives the recipient reason to believe that the message was created and sent by the stated sender.
Impossibility of denial: with a digital signature, the sender cannot deny that he or she sent the message after some time.
Integrity: the digital signature ensures that the message has not been altered in transmission.

The digital signature system uses asymmetric encryption. A pair of keys is needed to create a digital signature. The contents of the private key are known only to the sender’s owner, while the public key is available to all recipients because it is used to verify authenticity.

To sign a document, the sender must generate two keys: a private key and a public key. The private key is needed to sign the document and the public key is used to authenticate the document being sent. First a secure hash function is used to generate a hash value of the document content. This hash value, along with the sender’s private key, serves as input to the digital signature generation algorithm. This generates a digital signature attached to the text. Then, the content of the document with the attached signature is sent to the recipient. After successfully delivering the document and the sender’s digital signature, the recipient must verify that the document was sent by the person from whom it was expected to be sent. A hash value is calculated for the content of the delivered document. The hash value and the sender’s public key are provided as input to the digital signature verification algorithm. Two hash values are compared [4] in order to verify the document’s authenticity. If the signature passes the verification, it means that the document was really created by the sender and there were no changes during the sending. Otherwise, it proves that the document was intercepted and changed while it was being sent.

Thus, we can note the importance of digital signature in the electronic document management system. Digital signature is an effective means for ensuring document authenticity. Asymmetric encryption, hashing function and key pair (private and public key) are used when creating a digital signature. As a result of the authentication, you can make sure that the sender created and sent the document themselves, and that the context of the document was not changed during the sending process.