Key agreement using a key derivation key

A server, comprising:

• a communication interface and a processor, wherein the communication interface is configured to receive an identifier of a mobile device and the processor is configured to:
• access, based on the identifier, a secret key associated with the mobile device;
• evaluate a key derivation function to produce a key derivation key based on the secret key, wherein the key derivation function is based on a hash function;
• evaluate the key derivation function to produce an output value based on the key derivation key;
• and
• obtain a session key based on the output value.

A method performed by a mobile device, the method comprising:

• accessing a secret key in response to receiving a challenge value;
• evaluating a key derivation function to produce a key derivation key based on the secret key, wherein the key derivation function is based on a hash function;
• evaluating the key derivation function to produce an output value based on the key derivation key;
• obtaining a response value and a session key based on the output value;
• and
• transmitting the response value.

A device, comprising:

• a processor configured to:
• access a secret key in response to receiving a challenge value;
• evaluate a key derivation function to produce a key derivation key based on the secret key, wherein the key derivation function is based on a hash function;
• evaluate the key derivation function to produce an output value based on the key derivation key;
• obtain a response value and a session key based on the output value;
• transmit the response value to the wireless network operator system;
• access a sequence value previously stored on the device;
• obtain a message authentication code based on the secret key and the sequence value;
• and
• generate a device authentication token based on the message authentication code and the sequence value.