Encrypting Sensor Nodes with Advanced Encryption Standard (AES)

Wireless sensor network nodes with key management mechanism can be encrypted by AES as way of double security to prevent intruders from disrupting the communication between two sensor nodes and base station. It is an added version to make the network a further secured. The proposal is a modification to advance encryption standard and to improve the performance of AES in accommodating the key management system with due regard to low memory capability and energy consumption.

The new modification was implemented in Cooja, a Contiki operating system simulator. 16 bytes encryption was also generated to concur with the standard of AES needed for the encryption and decryption. We needed to provide an encryption key of length 128 bits at least. The AES is able to operate on 128, 192, or 256 bits of encryption key, but because we are limited by wireless sensor memory size, we decided to use 128 bits variant.

The problem with the Key Pre-Distribution Scheme that was used, in this case Blom’s Pairwise Key is that it provides only logq bits long encryption key where q is the top of the finite field  so if we wanted to have 128 bits long encryption key we would have to have G, D, A and K matrices over the finite field.

equation 1

So instead of generating G, D, A and K matrices over finite field we decided to generate set of 16 D matrices. Let s be the secure property (λ + 1)

 equation 2

 Therefore we must calculate set of 16 A matrices. Let s be the secure property (λ + 1)(λ + 1)

 equation 3

Now, we have to provide each node with a matrix P composed of rows from each of the A matrices. Let Pi represents matrix P composed of rows of 16 A matrices provided to node i

 equation 4

That way, it is possible to generate 16 pairwise keys with each node in the network and provide the keys to the AES algorithm. Let Gc be the column of G generated out of seed S(i) provided by node i  be the set of generated A  matrices and PK  be the column provided to AES as a encryption key, then:

 equation 5

                   equation 6

Key Management Encrypted with AES

About the Author

Celestine Iwendi is a Sensor and Electronics Researcher at the University of Aberdeen, UK.