Common use of Join Protocol Clause in Contracts

Join Protocol. The group has n members, {M1,..,Mn}. Every member in current group knows the existing key tree. The new member Mn+1 wishes to join the group by detecting the maximum signal strength of current group member to be as director in order to communicate in one hop and shortest distance. Later the new member sends, JOIN_MESSAGE, request message to director. The director refreshes the own session random key, computes keys and blinded keys of intermediate nodes up to the root node, and sends the existing key tree with its new session random key to new member. The insertion point of new member on key tree will be new root node of key tree because the new member can computed the information of new key tree with the lowest computation cost. The new member needs to compute only the blinded key at the new root node. Later, the new member updates existing key tree in accordance with creates a new root node and a new member node. Next, the new member selects session random key (i.e., secret key) and computes keys and blinded keys going up to the root. The blinded key of new member Mn+1 is BKn+1 = sn+1 βr βn+1 s-1 where βr is existing publish braid word at root node that the new member can find in existing key tree information. The new member broadcasts the new key tree containing only blinded keys to all other members. Finally all other members compute the new group key. This join protocol provides backward secrecy since director updated session random key that knowledge of a new member is unable to compute old group keys. Figure 3.4 shows situation before new member joins. After that, the Figure 3.5 shows an example of M4 joining a group where director as M2. This instance, it means that the M2 is nearest with M4 . The conclusion of join protocol is illustrated as follows: Step 1: The new member detects the maximum signal strength of current group members as director and sends JOIN_MESSAGE request message to join the group. After the director received the request message, it selected its new session random key, computes keys and blinded keys, and sends the existing key tree to new member. Step 2: The new member selected its session random key, updates key tree, computes keys and blinded keys, and broadcasts the new key tree containing the only all blinded key. Step 3: Each member computes the secret group key. 2 1 [1,0] [1,1] BK[1,1] = s3β -1 [0,0] 3 K[1,1] = s3 [2,0] M1 director -1 [2,1] M2 BK[2,1] = s β[1,0] s-1 K[2,1] = s2 [2,0] = s1 β[1,0] s1 K[2,0] =s1

Join Protocol. The current group has n members, {M1,..,Mn}the new member is identified with Mn+1. Every The tree will be added a new intermediate node with two children: the root node of the prior tree on the left and the new leaf node on the right for new member. This node becomes the new root node. As mention in section 3.3.2, the director who is the maximum signal strength with joining member in is selected from current group knows members. For simplicity, the existing key treeprotocol use n in the following to denote the number of group members before operation join. To deal with the join operation, a member is chosen as the director, because the new member detects the maximum signal strength. The new member Mn+1 wishes sends a join request, JOIN_MESSAGE, to join the group by detecting the maximum signal strength of current group member to be as director in order to communicate in one hop and shortest distancedirector. Later the new member sends, JOIN_MESSAGE, request message to director. The director refreshes the own session random key, computes keys and blinded keys of intermediate nodes up to the root node, node and sends the existing authenticated blinded keys in key tree with its new session random key to new memberMn+1. The insertion point of new Next, the member on Mn+1 computes the blinded keys in key tree will be new root node of key tree because the new member can computed the information of new key tree with the lowest computation cost. The new member needs to compute only the blinded key at the new root node. Later, the new member and updates existing key tree in accordance with creates a new root node and a new member node. Next, the new member selects session random key (i.e., secret key) and computes keys and blinded keys going up to the root. The blinded key of new member Mn+1 is BKn+1 = sn+1 βr βn+1 s-1 where βr is existing publish braid word at root node that the new member can find in existing key tree information. The new member broadcasts unicasts the new key tree containing only authenticated blinded keys to all other members. Finally all other members compute the new Finally, each member computes blinded keys and group key. This join protocol provides backward secrecy key independence since director updated updates session random key that knowledge of a new member is unable previous group key cannot be used to compute old the new group keyskey. Figure 3.4 4.1 shows situation before the authenticated key tree what director, M1, sends to new member joins. After thatmember, the Figure 3.5 shows an example of M4 joining a group where director as M2M4. This instance, it means that the M2 M1 is nearest with M4 M4. Figure 4.2 shows the authenticated key tree that M2 received from new member, M4. Figure 4.3 shows key tree information after M1 computes keys and blinded keys. The conclusion summary process of join protocol is illustrated as follows: Step 1: The new member detects the maximum signal strength of current group members as director and sends JOIN_MESSAGE request message to join the group. After the director received the request message, it selected its new session random key, computes keys and blinded keys, and sends the existing key tree to new member. Step 2: The new member selected its session random key, updates key tree, computes keys and blinded keys, and broadcasts the new key tree containing the only all blinded key. Step 3: Each member computes the secret group key. 2 1 [1,0] [1,1] BK[1,1] = s3β -1 [0,0] 3 K[1,1] = s3 [2,0] M1 director -1 [2,1] M2 BK[2,1] = s β[1,0] s-1 K[2,1] = s2 [2,0] = s1 β[1,0] s1 K[2,0] =s1