Function crypto_sign_ed25519_pk_to_curve25519 

pub fn crypto_sign_ed25519_pk_to_curve25519(
    x25519_public_key: &mut [u8; 32],
    ed25519_public_key: &PublicKey,
) -> Result<(), Error>

Converts an Ed25519 public key ed25519_public_key into an X25519 public key, placing the result into x25519_public_key upon success.

Compatible with libsodium’s crypto_sign_ed25519_pk_to_curve25519.

Errors

Returns an error if ed25519_public_key is noncanonical, has small order, is not on the curve, or is not in the main subgroup.