Function fromEdwards25519 [src]
Compute the Curve25519 equivalent to an Edwards25519 point.
Note that the function doesn't check that the input point is
on the prime order group, e.g. that it is an Ed25519 public key
for which an Ed25519 secret key exists.
If this is required, for example for compatibility with libsodium's strict
validation policy, the caller can call the rejectUnexpectedSubgroup function
on the input point before calling this function.
Prototype
pub fn fromEdwards25519(p: crypto.ecc.Edwards25519) IdentityElementError!Curve25519 Parameters
p: crypto.ecc.Edwards25519 Possible Errors
Source
pub fn fromEdwards25519(p: crypto.ecc.Edwards25519) IdentityElementError!Curve25519 {
try p.clearCofactor().rejectIdentity();
const one = crypto.ecc.Edwards25519.Fe.one;
const py = p.y.mul(p.z.invert());
const x = one.add(py).mul(one.sub(py).invert()); // xMont=(1+yEd)/(1-yEd)
return Curve25519{ .x = x };
}