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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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

For years the group has focused on a tree and missed the entire forest.

FORBES: PETA Still Has It All Wrong

As a local group becomes well known, tree owners will often come forward offering access to their unwanted apples or pears.

BBC: Ripe for the picking