For shared secrets, when a curve has a cofactor, the private key (in range of order) is multiplied by the cofactor before use. If there is a cofactor involved, check bit size of scalar against modulus instead of order.
For shared secrets, when a curve has a cofactor, the private key (in range of order) is multiplied by the cofactor before use. If there is a cofactor involved, check bit size of scalar against modulus instead of order.