A digital signature is a cryptographic technique that verifies the authenticity and integrity of a digital document, message, or transaction. It ensures that the content hasn’t been altered and that it was signed by the legitimate sender.

Digital signatures use public key infrastructure (PKI) technology. A private key is used to create the signature, and a corresponding public key is used to verify it. The private key is known only to the signer, and the public key is widely available.

Digital signatures are used for a wide range of applications, including document signing, email security, online contracts, legal documentation, secure communication, and electronic transactions.

To obtain a digital signature certificate, you need to contact a licensed Certifying Authority (CA) or a trusted service provider. They will guide you through the application process, which typically includes identity verification.

The validity of a digital signature certificate can vary but is usually one to three years, depending on the CA and your specific requirements. After the certificate expires, you will need to renew it to continue using it for secure transactions.