Ldasip: A Lightweight Dynamic Audit Approach for Sensitive Information Protection in Cloud Storage

Algorithm 2

Improved multibranch tree authentication structure construction algorithm.

	Inputs: {Ψ(Q, Ai), HASH, F}, List<TreeNode>
	Outputs: deputy root node R∗
	BUILDTREE(M,n,d,H,i)//Achievements: file information M, n blocks, tree height d,
	hash function H, traversal variable i.
	FILE INITIALIZATION(M)
	WHILE(CUR_DEPTH < d)//Build n-tree layer by layer until d-layer.
	{
	TreeNode tmp_father = new TreeNode ()
	HASH = 0//Current hash value
	List<TreeNode> tmp_up//Build temporary parent node
	FOR i = 1 TO m.size
	{
	IF (tmp_up.size() < n)//Have not formed a block, continue to traverse the nodes
	{
	tmp_up.add(m[i])
	hash = H(hash, m[i]- > hash)//Keep taking hash values
	m[i]- > Father = tmp_father//Set the father of the current node as “temporary father node”
	tmp_father - > Child.add(m[i])//Add a child to the “temporary father node”
	}
	ELSE
	{
	tmp_father- > hash = hash
	IF (CUR_DEPTH = = d/2)//Mark the deputy root node and add it to the result
	{
	tmp_father- > Q = 1
	R∗.add(tmp_father)
	}
	ELSE
	{
	tmp_father- > Q = 0
	}
	up.add(tmp_father)
	tmp_up.clear()
	tmp_father = new TreeNode()
	i  i-1
	}
	m = up;
	up.clear();
	++CUR_DEPTH;
	}
	return R∗