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Require cofactorless (unbatched) verification equation for EdDSA #25

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merged 1 commit into from
Feb 19, 2024

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@twiss twiss commented Feb 8, 2024

Resolve #19 by mandating the use of the cofactorless (unbatched) verification equation in Ed25519 and Ed448.

According to #19 (comment) and web-platform-tests/wpt#43751 (comment), this is already the current behavior of OpenSSL, BoringSSL, and Apple's CryptoKit. Hopefully this is true for other implementations as well, but let me know if there are any objections, of course.

Additionally, since Web Crypto does not have an API for batch signature verification, there seems to be no reason to use the cofactored (batched) equation.

By mandating one of the two equations, we reduce the risk of interoperability failures, as well as the risk of this (potential) difference being used to fingerprint implementations.


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This is what Safari's and Chrome's implementation already provide, and as far as I know, most of the non-web implementations also do.

@twiss twiss merged commit 067671c into main Feb 19, 2024
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@twiss twiss deleted the require-unbatched-equation branch February 19, 2024 16:57
github-actions bot added a commit that referenced this pull request Feb 19, 2024
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@javifernandez javifernandez mentioned this pull request Apr 1, 2024
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Dichotomy between verification equations for EdDSA
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