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path: root/Documentation/technical/hash-function-transition.txt
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2018-03-27doc hash-function-transition: clarify what SHAttered meansLibravatar Ævar Arnfjörð Bjarmason1-5/+24
Attempt to clarify what the SHAttered attack means in practice for Git. The previous version of the text made no mention whatsoever of Git already having a mitigation for this specific attack, which the SHAttered researchers claim will detect cryptanalytic collision attacks. I may have gotten some of the nuances wrong, but as far as I know this new text accurately summarizes the current situation with SHA-1 in git. I.e. git doesn't really use SHA-1 anymore, it uses Hardened-SHA-1 (they just so happen to produce the same outputs 99.99999999999...% of the time). Thus the previous text was incorrect in asserting that: [...]As a result [of SHAttered], SHA-1 cannot be considered cryptographically secure any more[...] That's not the case. We have a mitigation against SHAttered, *however* we consider it prudent to move to work towards a NewHash should future vulnerabilities in either SHA-1 or Hardened-SHA-1 emerge. Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-03-27doc hash-function-transition: clarify how older gits die on NewHashLibravatar Ævar Arnfjörð Bjarmason1-3/+8
Change the "Repository format extension" to accurately describe what happens with different versions of Git when they encounter NewHash repositories, instead of only saying what happens with versions v2.7.0 and later. See ab9cb76f66 ("Repository format version check.", 2005-11-25) and 00a09d57eb ("introduce "extensions" form of core.repositoryformatversion", 2015-06-23) for the relevant changes to the setup code where these variables are checked. Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-09-28technical doc: add a design doc for hash function transitionLibravatar Jonathan Nieder1-0/+797
This document describes what a transition to a new hash function for Git would look like. Add it to Documentation/technical/ as the plan of record so that future changes can be recorded as patches. Also-by: Brandon Williams <bmwill@google.com> Also-by: Jonathan Tan <jonathantanmy@google.com> Also-by: Stefan Beller <sbeller@google.com> Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>