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0 基础也能打的 CTF

中国科学技术大学第八届信息安全大赛(aka Hackergame)在 2021 年 10 月 23 日如期而至——

在一个风和日丽的下午,某个不知天高地厚的的热心市民决定试一试深浅…


最终排名 55,比去年进步了 10 倍以上,好耶!

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我如果想要知道一个字节从一个终端经由TCP传输到另一个终端所耗费的时间,即 TCP 的传输延迟(Latency),应该怎么办?

经过查阅相关信息,发现了两种方案:

  1. TCPing(绝大部分答案,但真的如此吗?)
  2. 通过手动构造 TCP SYN 包来测量延迟(github.com/grahamking/latency

然后还有我的灵光一现…

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In computer science, an AVL tree (named after inventors Adelson-Velsky and Landis) is a self-balancing binary search tree. It was the first such data structure to be invented.[2] In an AVL tree, the heights of the two child subtrees of any node differ by at most one; if at any time they differ by more than one, rebalancing is done to restore this property. Lookup, insertion, and deletion all take O(log n) time in both the average and worst cases, where $n$ is the number of nodes in the tree prior to the operation. Insertions and deletions may require the tree to be rebalanced by one or more tree rotations.

Wikipedia

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