Description of Algorithms Sample Clauses

Description of Algorithms. In this subsection, we present three interval-based dis- tributed rekeying algorithms. They are the Rebuild algo- rithm, the Batch algorithm and the Queue-batch algorithm. The use of interval-based rekeying aims to maintain good rekeying performance, independent of the dynamics of joins and leaves. The three distributed algorithms are developed based on the following assumptions: The key tree of TGDH is used as a foundation of all the algorithms. The rekeying operations are carried out at the begin- ning of every rekey interval. There exists a virtual queue holding all join and leave requests till the be- ginning of the next rekey interval. When a new member sends a join request, it should also include its individual blinded key. For simplicity, all clients know the existing key tree structure and they also know all the blinded keys within the tree structure. The group members would elect sponsors to be respon- sible for computing and broadcasting blinded keys. To obtain the blinded keys of the renewed nodes (a node is said to be renewed if it is a non-leaf node and its as- clients contribute to the composition of the group key. The pseudo code of the Batch algorithm is given as: sociated keys are updated), the key paths of the spon- sors should contain those renewed nodes. Since the interval-based rekeying operations involve nodes lying on more than one key paths, more than one sponsors may be elected. Also, a renewed node may be rekeyed by more than one sponsor. In this case, we assume that the sponsors can coordinate with one another such that the blinded keys of all the renewed nodes are only broadcast once. We adopt the following notations for the three distributed algorithms. Let denote the existing key tree. Assume that existing members = wish to leave, and new members = wish to join the communication group within a rekey interval.

Description of Algorithms. In this subsection, we present three interval-based dis- tributed rekeying algorithms. They are the Rebuild algo- rithm, the Batch algorithm and the Queue-batch algorithm. The use of interval-based rekeying aims to maintain good rekeying performance independent of the dynamics of joins and leaves. The three distributed algorithms are developed based on the following assumptions: The rekeying operations are carried out at the begin- ning of every rekey interval. There exists a virtual queue holding all join and leave requests till the be- ginning of the next rekey interval. obtain the blinded keys of the renewed nodes (a node is said to be renewed if it is a non-leaf node and its as- clients contribute to the composition of the group key. The pseudo code of the Batch algorithm is given as: sociated keys are updated), the key paths of the spon- sors should contain those renewed nodes. Since the interval-based rekeying operations involve nodes lying on more than one key paths, more than one sponsors may be elected. Also, a renewed node may be rekeyed by more than one sponsor. In this case, we assume that the sponsors can coordinate with one another such that the blinded keys of all the renewed nodes are broadcast once only. We adopt the following notations for the three distributed algorithms. Let T denote the existing key tree. Assume that L 0 existing members M l = hM l; ;M l i wish to Xxxxx (T , M j , J , M l, L) 1. if (L == 0) f /* pure join case */

Description of Algorithms public function construct(Point g); The constructor serves only to populate the generator point for ECDH. public function getPublicPoint(); When called, this method generates a pseudo-random number ”secret” between 0 and the order of the generator point. Upon successful generation it returns the public point secret*Generator. public function setPublicPoint(Point q); This method is used to set a public point that was received from the person wishing to establish secure communication through an untrusted channel. public function calculateKey(); The calculateKey method’s purpose is to finally establish the shared secret. When both parties call this method, they both arrive at the same key. Find the explanation of cor- rectness behind ECDH in Section 3. public function encrypt(string); public function decrypt(string); public function encryptFile(path); public function decryptFile(path); The methods above are demonstrations of how a dual-key encryption scheme may be used with the ECDH shared key agreement protocol. The first pair of methods may be used for arbitrary strings. For hashing the x value of the generated shared secret, the implemen- tations use SHA256. This hash is then fed into the 256 bit EAS encryption function in CBC mode. The methods which operate on files are identical to the previous two, but are designed to read in a file as the message to be communicated between Xxxxx and Xxx.