The primary function of a security protocol in data transmission is to ensure the confidentiality, integrity, and authenticity of data being communicated over networks. Security protocols such as SSL/TLS and IPsec encrypt data, making it unreadable to unauthorized interceptors, thereby protecting sensitive information from eavesdropping. Additionally, these protocols verify the identities of communicating parties, ensuring that data is sent and received by trusted entities. This is critical for secure online transactions, communications, and data exchanges in today’s digital environment.