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keyfork-derive-openpgp: when converting ed25519 to cv25519, apply clamp operation

This commit is contained in:
Ryan Heywood 2024-01-21 18:10:36 -05:00
parent 019e390b94
commit 3b42ba5f00
Signed by: ryan
GPG Key ID: 8E401478A3FBEF72
1 changed files with 8 additions and 1 deletions
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9
crates/derive/keyfork-derive-openpgp/src/lib.rs
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@ -110,9 +110,16 @@ pub fn derive(data: DerivationResponse, keys: &[KeyFlags], userid: &UserID) -> R
let subkey = if is_enc && is_non_enc {
return Err(Error::InvalidKeyFlags(subkey_flags.clone()));
} else if is_enc {
// Clamp key before exporting as OpenPGP. Reference:
// https://gitlab.com/sequoia-pgp/sequoia/-/blob/main/openpgp/src/crypto/backend/rust/asymmetric.rs (see: generate_ecc constructor)
// https://github.com/jedisct1/libsodium/blob/b4c5d37fb5ee2736caa4823433926b588911e893/src/libsodium/crypto_scalarmult/curve25519/ref10/x25519_ref10.c#L91-L93
let mut bytes = PrivateKey::to_bytes(derived_key.private_key());
bytes[0] &= 0b1111_1000;
bytes[31] &= !0b1000_0000;
bytes[31] |= 0b0100_0000;
Key::from(
Key4::<_, SubordinateRole>::import_secret_cv25519(
&PrivateKey::to_bytes(derived_key.private_key()),
&bytes,
None,
None,
epoch,