A vehicle comprising a vehicle communication manager device for wirelessly accessing subscription data services for the vehicle, the device comprising: a memory comprising a non-volatile memory device storing a fixed embedded public key, wherein the embedded public key is a public key of a public-private key pair associated with a data service system not onboard the vehicle; a processor in communication with a wireless datalink transceiver; the processor programed to execute code to implement a vehicle data service protocol, wherein in accordance with the vehicle data service protocol, the processor is configured to initiate a communication session for data service exchanges with the data service system via the wireless datalink transceiver; wherein in accordance with the vehicle data service protocol, the processor is configured to perform a subscription validation sequence to: transmit a session request message to the data service system; and validate an authenticity of a session reply message received from the data service system using the embedded public key, wherein the session reply message includes a public operational authentication key, a public operational encryption key, and is signed with a subscriber validation private key that corresponds to a private key of a public-private key pair associated with the embedded public key; wherein in accordance with the vehicle data service protocol, the processor is configured to perform a session initiation sequence to: transmit an initialization request message to the data service system, the session request message including a key derivation key generated onboard the vehicle, wherein the key derivation key in the initialization request message is encrypted using the public operational encryption key; validate an authenticity of an initialization response message received from the data service system using the public operational authentication key; and in response to affirmatively validating the initialization response message, apply the key derivation key to a key derivation function to generate a message authentication key; wherein the processor is configured to authenticate data service uplink messages received from a host data service of the data service system during the communication session using the message authentication key. a memory comprising a non-volatile memory device storing a fixed embedded public key, wherein the embedded public key is a public key of a public-private key pair associated with a data service system not onboard the vehicle; a processor in communication with a wireless datalink transceiver; the processor programed to execute code to implement a vehicle data service protocol, wherein in accordance with the vehicle data service protocol, the processor is configured to initiate a communication session for data service exchanges with the data service system via the wireless datalink transceiver; wherein in accordance with the vehicle data service protocol, the processor is configured to perform a subscription validation sequence to: transmit a session request message to the data service system; and validate an authenticity of a session reply message received from the data service system using the embedded public key, wherein the session reply message includes a public operational authentication key, a public operational encryption key, and is signed with a subscriber validation private key that corresponds to a private key of a public-private key pair associated with the embedded public key; transmit a session request message to the data service system; and validate an authenticity of a session reply message received from the data service system using the embedded public key, wherein the session reply message includes a public operational authentication key, a public operational encryption key, and is signed with a subscriber validation private key that corresponds to a private key of a public-private key pair associated with the embedded public key; wherein in accordance with the vehicle data service protocol, the processor is configured to perform a session initiation sequence to: transmit an initialization request message to the data service system, the session request message including a key derivation key generated onboard the vehicle, wherein the key derivation key in the initialization request message is encrypted using the public operational encryption key; validate an authenticity of an initialization response message received from the data service system using the public operational authentication key; and in response to affirmatively validating the initialization response message, apply the key derivation key to a key derivation function to generate a message authentication key; transmit an initialization request message to the data service system, the session request message including a key derivation key generated onboard the vehicle, wherein the key derivation key in the initialization request message is encrypted using the public operational encryption key; validate an authenticity of an initialization response message received from the data service system using the public operational authentication key; and in response to affirmatively validating the initialization response message, apply the key derivation key to a key derivation function to generate a message authentication key; wherein the processor is configured to authenticate data service uplink messages received from a host data service of the data service system during the communication session using the message authentication key.