提出了基于哈希表和平衡二叉树的证书撤销方案，并分析了该方案的有效性和安全性。

This paper proposes a promoted certificate revocation based on Hash table and balanced binary tree, and gives the analysis of validity and security.

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二叉树平衡的条件是左子树平衡且右子树平衡且左右子树的高度相差最多为1。基于这个思路递归处理。

For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1.

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