X =
00
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
Y =
00
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
X ↔ Y
Ext-GCD(10, 14) → Twos = 1 → Ext-GCD(5, 7) :
i
GCD
Bezout
AOdd :
AEven :
A
↔
B
ax
ay
bx
by
|A-B|
A↔B
Sx
Sy
ax ←
Sx' ay ←
Sy' A ←
A/2 ax ←
ax + Y ay ←
ay + X ax ←
ax/2 ay ←
ay/2
0
5
7
1
0
0
1
1
5
7
1
0
0
1
2
1
1
1
1
1
1
8
6
4
3
2
1
↔
5
4
3
1
0
4
1
5
3
5
3
2
12
8
6
4
3
2
1
6
4
4
3
1
1
Even
Even
3
2
4
1
1
3
2
4
3
0
5
1
1
3
2
4
3
0
6
1
1
3
2
4
3
0
7
1
1
3
2
4
3
0
(3)(10) - (2)(14) = 2