What is used to ensure that message was sent from a particular person and ensures that the message was not altered?

Digital signatures are used to ensure that a message was sent by a specific person and that it has not been altered during transmission. They employ cryptographic techniques, where the sender signs the message with their private key, creating a unique signature. The recipient can then verify this signature using the sender's public key, confirming both the authenticity of the sender and the integrity of the message.