As more and more components and actions are being available in digital forms, signatures are also becoming digitized. The classic ink and paper signature is being replaced by digital signatures. A digital signature is a unique code assigned to an individual or organization that is used to authenticate documents and ensure untampered transfer to the receiver. 

The basic principle of using digital signatures is that the sender holds a private key that they use to “sign” or encrypt an electronic document. When the document is sent to the receiver, they use the public key that they obtained from the sender to decrypt it. Asymmetric cryptosystems are utilized for the key generation process. 

The authenticity of the identity of the signer and the document is ensured through a digital signature certificate or DSC. The DSC contains all the credentials of the signer that prove their identity. To buy a digital signature, a person or organization must apply for a DSC from an approved Certifying Authority and get themselves verified and approved using legal identification documents admitted by the authority. 

These certificates are usually active for a finite validity period, after which it must be renewed or the license to use the signature will be revoked and their key invalidated. After a person get digital signature and receives the associated private key, it is of utmost importance that they store it with the utmost security and responsibility. 

The three main purposes served by digital signatures is to prove the authenticity of the document and its source, to ensure that the contents of the document have not been tampered with, and to verify the identity of the sender. Besides security, digital signatures also come with the advantage of reducing the cost, time, and effort expended in signing and sending back official documents.