X_PRIVATE_BYTES
const uint8_t scalar[X_PRIVATE_BYTES])
const uint8_t scalar[X_PRIVATE_BYTES])
uint8_t scalar2[X_PRIVATE_BYTES];
scalar2[X_PRIVATE_BYTES - 1] &= ~((0u - 1u) << ((X_PRIVATE_BITS + 7) % 8));
scalar2[X_PRIVATE_BYTES - 1] |= 1 << ((X_PRIVATE_BITS + 7) % 8);