Authentication is the first step toward establishing a service provider and customer association. In a mobile network environment, a lightweight and secure authentication protocol is one of the most significant factors to enhance the degree of service persistence. This work presents a secure and lightweight keying and authentication protocol suite termed time-assisted authentication protocol (TAP). The TAP improves the security of protocols with the assistance of time-based encryption keys and scales down the authentication complexity by issuing a reauthentication ticket. While moving across the network, a mobile customer node sends a reauthentication ticket to establish new sessions with service-providing nodes. Consequently, this reduces the communication and computational complexity of the authentication process. In the keying protocol suite, a key distributor controls the key generation arguments and time factors, while other participants independently generate a keychain based on key generation arguments. We undertake a rigorous security analysis and prove the security strength of TAP using communicating sequential processes and rank function analysis.