What is the main use of a digital signature?

A digital signature plays a crucial role in ensuring the integrity of data. By using a digital signature, the origin of the message and its consistency can be verified. When a sender signs a piece of data with their private key, it creates a unique hash value that corresponds to the signed data. When the recipient receives it, they can use the sender's public key to validate the signature and check that the data has not been altered during transmission. If even a single character of the message is changed, the verification will fail, indicating that the integrity of the original data has been compromised.

While encryption is a primary function in security, its purpose is to keep data confidential rather than verify its integrity. Improving data storage is not relevant to digital signatures, as they are not involved in how data is stored. Similarly, managing user identities pertains more to access control and authentication mechanisms rather than providing the integrity assurance that digital signatures are designed for. Thus, the verification of data integrity is the fundamental and primary use of digital signatures.