7.8. A DISCUSSION ON SECURITY 111
Algorithm 7.12 Image Build
1: Cluster head assigns virtual ids to sensors.
2: Nodes in the cluster store dissemination packets corresponding to their virtual ids.
3: Encrypted packets are verified using hashes and then decrypted.
4: Decrypted packets with hashes are combined in large blocks and securely broadcasted in
the cluster.
5: All nodes receive all the transmitted code.
6: VHT and HHT are verified.
7: Base station broadcasts the CFL.
8: Nodes receive encrypted common functions from other nodes.
9: Functions are decrypted and verified through BF.
10: if functions are verified then
11: Build code image.
12: if all functions are verified then
13: Reboot with new code.
14: end if
15: end if
7.8 A DISCUSSION ON SECURITY
Our algorithm divides an application’s code into two parts: new code and the common code.
Different mechanisms are used for the security of both these categories, which are discussed in
the following subsections.
7.8.1 CONFIDENTIALITY OF CODE
New Code
Confidentiality of the new code is provided by encrypting the dissemination content with the
session key (S
n
). is key is created uniquely for each session by using the cluster’s key CK and
a randomly generated nonce (n). is nonce is sent in the signature packet with the VHT root
hash, and the signature over (VHT root hashjjn). e signature guarantees the correct reception
of both the VHT root hash and the nonce n.
Common Code
Confidentiality of the common code is provided by proxy re-encryption. e following dis-
cussion is based on the EC-BBS proxy re-encryption scheme, although a similar argument
can also be made using SRE [119]. In the pre-deployment phase, the base station encrypts
randomly chosen functions with the encryption key Q
0
using EC-BBS and stores them on
the nodes. Neither this key Q
0
nor the corresponding secret key K
0
are revealed to any node.
is provides the confidentiality of the common functions from the nodes on which the func-
..................Content has been hidden....................
You can't read the all page of ebook, please click here login for view all page.