Google 與 CWI Amsterdam 合作,找到 SHA-1 第一個 collision

GoogleCWI Amsterdam 正式攻陷 SHA-1:「Announcing the first SHA1 collision」,然後也沒什麼意外的,現在大家都喜歡針對各種安全問題註冊一個 domain 來介紹:「SHAttered」。

shattered-1.pdfshattered-2.pdf 下載下來確認,可以看出來兩個不一樣的檔案有同樣的 SHA-1 value:

gslin@home [/tmp] [21:33/W4] sha1sum *.pdf
38762cf7f55934b34d179ae6a4c80cadccbb7f0a  shattered-1.pdf
38762cf7f55934b34d179ae6a4c80cadccbb7f0a  shattered-2.pdf

gslin@home [/tmp] [21:33/W4] sha256sum *.pdf
2bb787a73e37352f92383abe7e2902936d1059ad9f1ba6daaa9c1e58ee6970d0  shattered-1.pdf
d4488775d29bdef7993367d541064dbdda50d383f89f0aa13a6ff2e0894ba5ff  shattered-2.pdf

直接拿 pdf 來打,表達的是「一次到位」以及「既然可以攻擊 pdf,那麼其他東西當然也有可能」...

攻擊計算量的部份,這次攻擊使用的資源其實不算少,但對於大公司與大單位已經不是問題了,猜這次 Google 應該是贊助不少雲端設施:

  • 6,500 years of CPU computation to complete the attack first phase
  • 110 years of GPU computation to complete the second phase

這衍生出另外一個頭比較大的問題是 Git 目前使用的 SHA1:

GIT strongly relies on SHA-1 for the identification and integrity checking of all file objects and commits. It is essentially possible to create two GIT repositories with the same head commit hash and different contents, say a benign source code and a backdoored one. An attacker could potentially selectively serve either repository to targeted users. This will require attackers to compute their own collision.

這下得來看 Git 核心團隊要怎麼從 SHA-1 migrate 到其他 hash function 了...

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3 Responses to Google 與 CWI Amsterdam 合作,找到 SHA-1 第一個 collision

  1. Pingback: 對 SHA-3 的攻擊 | Gea-Suan Lin's BLOG

  2. Chikei says:

    單論git應該是還好,當初就有考慮到collision了
    http://marc.info/?l=git&m=115678778717621&w=2

  3. Pingback: Git 支援其他 Hash 演算法的進展 | Gea-Suan Lin's BLOG

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