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Git 3.0's upcoming SHA-256 default will be a costly mistake

570 points · 536 comments · chmaynard

  1. meinersbur · · focus · HN ↗
    Linus Torvalds in 2007:

    > but the point is the SHA-1, as far as Git is concerned, isn't even a security feature. It's purely a consistency check. The security parts are elsewhere, so a lot of people assume that since Git uses SHA-1 and SHA-1 is used for cryptographically secure stuff, they think that, Okay, it's a huge security feature. It has nothing at all to do with security, it's just the best hash you can get. ... [1]

    [1] <a href="https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=4XpnKHJAok8&amp;t=56m20s" rel="nofollow">https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=4XpnKHJAok8&amp;t=56m20s

    So Torvalds used SHA-1 purely because he needed a hash function with no other property than identifying content.

    1. zamalek · · focus · HN ↗
      Exactly. But that&#x27;s why I think SHA was a mistake. He should have gone with something like murmur to avoid all this frothing at the mouth.
      1. layer8 · · focus · HN ↗
        It was a mistake to assume a fixed algorithm in the repository format and client-server protocol. I remember being surprised when I learned about that choice, being familiar with cryptographic protocols and formats where the hash algorithm is usually a parameter that can vary for each concrete hash.
        1. loeg · · focus · HN ↗
          &gt; being familiar with cryptographic protocols and formats where the hash algorithm is usually a parameter that can vary for each concrete hash.

          This flexibility (&quot;agility&quot;) in cryptographic protocols is often seen as a mistake today, actually.

          1. WorldMaker · · focus · HN ↗
            Cryptographic protocols have been moving towards something of a compromise in flexibility. &quot;Everything flexible&quot; is a security risk, especially when &quot;everything&quot; includes &quot;fallback to nothing secure&quot;. &quot;No flexibility&quot; is a security risk because you can&#x27;t upgrade. The middle path is something like &quot;version numbers&quot; with hard breakpoints. &quot;I only support v2 of this cryptographic protocol and will not fallback to v1.&quot;

            Which is sort of the hash algorithm approach git is taking with incompatible versions and a version break.

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