给定哈希长度的通用生日计算 [英] Generalised Birthday Calculation Given Hash Length

问题描述

让我们假设我们得到以下信息:

Let us assume that we are given the following:

• 哈希的长度
• 获得碰撞的机会

现在，了解了以上内容，我们如何获得获得给定机会百分比所需的样本"数量?

Now, knowing the above, how can we obtain the number of "samples" needed to obtain the given chance percentage?

推荐答案

当我们将Simplified formula用作生日悖论时，我们得到:

When we take the Simplified formula for the birthday paradox we get:

probability = k^2/2N

所以:

sqr(probability*2*n) = k

我们知道n = 2 ^ lenghtHash

Where we know that n = 2^lenghtHash

一个小测试: 哈希= 16位:N = 65536 概率= 50％= 0.5

A small test: Hash = 16 bit : N= 65536 probability = 50% = 0.5

sqr(0.5 * 2 * 65536)= 256 samples

sqr(0.5*2*65536) = 256 samples

这不是100％正确，因为我们从简化公式开始，但是对于大哈希和更大样本集，它变得非常接近.

This is not 100% correct as we started of with the Simplified formula, but for big hashes and lager sample sets it gets very close.

有关公式的链接，您可以此处.

for a link on the formula you can look here.

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