Fig. 2
From: A fully dynamic forward-secure group signature from lattice
For example, there is a tree with \(2^3=8\) leaves representing 8 time periods. For each level in the path of the target node (010) which stands for time periods \(T=2\), we add its right sibling to the set \(Nodes_{(2\rightarrow 7)}\). Then we have \(Nodes_{(2\rightarrow 7)}=\{(1)^{\top },\perp ,(011)^{\top },(010)^{\top }\}\)