n . : n=p*q. p<<q, .
.
EC(Zn) P0 kP0 = ∞ (mod p) (*), p n.
#EC : [p + 1 -2√p, p + 1 + 2√p].
:
Zn EC(Zn): y2= x3 + ax + b, 0 < a,b <p.
: //
1. B1, , B1 = 10000.
2. x, y, a [0, n − 1].
3. b = y2−x3−ax mod n g = (n, 4a3+27b2).
g = n, .2. 1 < g < n,
. , E: y2= x3+ ax + b
- P0(x, y).
4. P(x, y) , P0.
:
= p1k1 * p2k2 * * ptkt .
r=max piki (i < t) , pr < B1.
P= P0 :
P1= ∏ piti P, piti < B1,
P pr.
, , B1, ,
(n, P1) = d > 1.
, n .
, B1 ,
.
: //
, #EC
q, 1-
B1.
1. B2, [B1; B2]: {q1, q2,..., qm }.
2. q1 P, q2 P, q3 P,...
B2, (*).
() , .
, , .
, P(x) ri xi, .
- , .. x y, .
E: K, f(x,y): E → K - . f , P ∈ E, f(P) = 0 f(P) = ∞. f,
|
|
f. f , . f () k P, f , up P () , up f P.
6.1. E: k. D E ,
rP rP
. P, , (support) D supp(D). P ∈ supp(D), D deg(D).
, , D sum(D).
. , , 0. , (principal divisors).
l: ax + by + c, P1(x1, y1) P2(x2, y2) E. l .P1 P2, E .P3(x3, y3), ∞. P1, P2 P3 l 1 , . ∞ 3 . , :
(1) (2).
(1) , x/y 0 .∞, (2) , x/y .∞ .∞ . .∞ 2 x. y = x (y/x), .∞ 3 y l = Ax + By + C. l (3). .P3 v = x x3. .P3(x3, y3), −P3(x3, −y3) .∞,
. (4)
(3) (4)
P1 + P2 = −P3 E, (5).
(3) (4) , 6.1 lP1,P2 0, ∞, , :
6.2. D E, 0, , sum(D) = ∞.
, (7), K, .. f(D1 + D2) = f(D1) f(D2), f(D1 − D2) = f(D1)/f(D2) (6)
(6) , (7).
6.3.( ) f g ,
div(f) div(g) ,
: f(div(g)) = g(div(f)).