Depending on what you think the "issue" is, one of: * wrapping is well-defined behavior for unsigned integers; signed integer wrapping is UB, but is not used h

Depending on what you think the "issue" is, one of: * wrapping is well-defined behavior for unsigned integers; signed integer wrapping is UB, but is not used here. * the equations (that a & b cancel each other out, resulting in the swap) hold even when done in a mod N ring.