What is the primary purpose of a digital signature?

The primary purpose of a digital signature is to verify the identity of the sender and validate the document's integrity. Digital signatures utilize cryptographic techniques to provide assurance that the message or document has not been altered in transit and that it genuinely comes from the claimed sender. This is achieved through the use of a public-private key pair; the sender signs the document with their private key, and anyone with access to the corresponding public key can verify the signature.

This process is critical in environments where trust and authenticity are paramount, such as in legal contracts, financial transactions, and sensitive communications. The ability to confirm both the sender's identity and the integrity of the information protects against forgery and tampering, thereby ensuring the reliability of electronic communications.

In contrast to other choices, ensuring document confidentiality is primarily the role of encryption, while the compression of documents is unrelated to digital signatures and serves a different purpose in data management. The verification of identity and the integrity of the message are the cornerstone functionalities that establish trust in digital transactions.