An inclined tree-group key management scheme based on elliptic curve cryptosystem is presented in this paper, which needs to renew only several node keys to provide perfect secrecy.

本文提出基于椭圆曲线密钥体制的斜树密钥管理方案，算法只需更新少量密钥就能满足系统的安全需求。

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Members of the research group stand atop the stump of a giant redwood tree.

研究项目组的成员站在一块巨大的红木树桩上。

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A group of boys gathered around a tree.

一群男孩聚集在一棵树旁。

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The American Christmas Tree Association, the artificial-tree retailers' group, said it welcomes a stronger marketing effort from live Christmas tree farmers.

WSJ: Fir Real? Christmas Trees in Crisis as Americans Flock to Fakes

To do so he looked at three well-studied parts of the linguistic family tree: the Bantu languages of Africa, the Indo-European group from Eurasia and the Austronesians of the Pacific.

ECONOMIST: Languages and species evolve in surprisingly similar ways

The group's campaign manager Colin Watson said it was not about being "anti-tree".

BBC: Holyrood members' bill bids to outlaw high hedges