@jedisct1 We're currently using libsodium for scalar multiplication on curve ed25519 at my workplace. when we multiply by the order + 1 we don't get back the same point... is this some implementation quirk? or are we misguided? insight would be much appreciated. thank you!
crypto_scalarmult() sets bit 126 of the scalar. This is part of the X25519 design, to help avoid side channels in new implementations. So you’re not effectively multiplying by order+1.