ed: Change SigningKey::to_scalar back to SigningKey::to_scalar_bytes
#599
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This is a breaking change that would break running code, namely @dignifiedquire is using these conversions to instantiate a dalek-cryptography/ed25519-dalek#296 That's all working just fine and the existing API is useful. If you really want to go through with this, you either need to deprecate |
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To be clear: I'm fine with adding |
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Ok agreed. I think simply adding it would be fine. And updating the docs on |
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Alright, ready to review again |
tarcieri
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Nov 14, 2023
This was referenced Nov 14, 2023
mikelodder7
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Feb 17, 2024
* Brought back SigningKey::to_scalar_bytes; added regression test * Updated SigningKey::to_scalar docs and tests
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As mentioned in the conversation in #565, it is currently not clear how you would use a clamped and reduced scalar from
SigningKey::to_scalar()to build an x25519 keypair. In fact, the test code in that thread shows thatx25519_dalek::PublicKey::from(StaticScalar::from(sk.to_scalar().to_bytes()))does not match the ed25519 public key. This is because the second public key computation does clamping again, so it's clamp -> reduce -> clamp, which is not a no-op.This PR replaces
SigningKey::to_scalar()withSigningKey::to_scalar_bytes(), which returns the unreduced scalar bytes determined by the ed25519 secret key. This is actually how things used to be before #545, and what the docs (currently erroneously) reflect.I've also added a regression test to the ed25519 tests.