The leftmost four bits define the sign.

The leftmost bit is treated as the most significant bit.

Let be the leftmost bits of , where is the bit length of the group order .

Let be the leftmost bits of .

In the end, if then those two leftmost bits will be 11 and Bob will answer that .

And so now k and k have a unique location, being distinguished by the first two leftmost bits.

The leftmost four bits are considered ample headroom for calculations.

Shift b one bit to the right, discarding the rightmost bit, and making the leftmost bit have a value of zero.

Keep track of whether the leftmost bit of a is set to one and call this value carry.

Shift a one bit to the left, discarding the leftmost bit, and making the new rightmost bit zero.