Key management

A method for generating keys for security processing of communication between a transmitting communication unit and a receiving communication unit of a sensor network, wherein the transmitting communication unit and the receiving communication unit are adapted to obtain knowledge about a secret function, the method comprising:

• receiving a value in association with cryptographically processed data, the value among a finite set of values,
• calculating a key based on the secret function and the received value at the receiving unit, and
• processing the received data with the generated key,
• wherein the secret function has been selected from a set of functions, wherein the set of functions is almost k-wise independent, and
• wherein the secret function is shared between the communication units and pre-configured independently and randomly to the communication units,
• the generated key is only based on information of the transmitting communication unit and that one of the communicating units is a central point and the other is a sensor wherein the key is generated securely despite k being independent of the number of sensors in the sensor network.

A first communication unit configured to generate keys for cryptographic processing that are set to be used for communication between the first communication unit and a second communication unit in a sensor network, wherein the first communication unit and second communication unit are knowledgeable regarding secret function, the first communication unit comprising:

• a processing system configured to cause:
• selecting a value from among a set of values;
• calculating a key from the secret function and the selected value;
• processing data with the calculated key;
• and
• transmitting the processed data in association with the selected value to the second communication unit,
• wherein the secret function is from a set of functions, wherein the set of functions is almost k-wise independent,
• wherein the secret function is shared between the first and second communication units and pre-configured independently and randomly to the first and second communication units, and that the key is only based on information of the first communication unit, and that one of the first and/or second communicating units is a central point and the other is a sensor wherein the key is generated securely despite k being independent of the number of sensors in the sensor network.

A communication unit configured to generate keys for communications that are to be sent over a communications network, the communication unit adapted to obtain a secret function, the communication unit comprising:

• a processing system configured to cause:
• receiving a value a predetermined set of values;
• generating a key based on applying the received value to the secret function
• processing data with the generated key;
• and
• transmitting the processed data to a receiving device,
• wherein the secret function is one of a plurality of functions and the plurality is at least substantially k-wise independent,
• wherein the secret function is shared with at least one other communication unit, and that the generated key is based on information from the at least one other communication unit, and wherein the generated key is independent of a number of units within the communications network.