對 GitHub 的 Public Key 分析

Hacker News Daily 上看到有人針對 GitHub 上的 Public Key 分析:「Auditing GitHub users’ SSH key quality」。

這個分析主要用的是 GitHub 的 .keys 功能取得:

A little known feature of GitHub is the ability to look at the public SSH keys that other users have set to be authorised on their account (for example https://github.com/torvalds.keys)

作者從去年 2014 年 12 月 27 日跑到今年 2015 年 1 月 9 日,共取得了 1376262 把 public key,然後就針對這些 key 分析。

「The Debian bug bites again」這一段講的是 CVE-2008-0166 (可以參考「該換 ssh keys 了」這篇的說明),發現即使是七年後的現在,也還是有問題。

另外還有 256 bits 與 512 bits 的 RSA key,作者自己建立了一把測試,用 i5-2400 只要 25 分鐘就可以解出 256 bits 的 private key:

This risk isn’t only real if someone had gathered together top of the line mathematicians or supercomputers worth of power, the 256 bit key I factored was factored on a i5-2400 in 25 mins.

NSA 應該都摸透了...

作者提供的時間線:

[27th December 2014] Key Crawl Started
[28th Feb 2015] Disclosed low bits issue to a peer at GitHub
[1st March 2015] Discovered the weak Debian Keys (and disclosed)
[5th May 2015] Debian keys revoked, emails sent out
[1st June 2015] Weak and low quality keys revoked

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