Function ed25519_verifier 

pub fn ed25519_verifier(
    algorithm: &str,
    public_key: &[u8],
    message: &[u8],
    signature: &[u8],
) -> Result<(), String>

Real Ed25519 verifier. Use as the verifier callback when the composite contains an Ed25519 component. Returns Ok if the Ed25519 component verifies.