**EC Cryptography Tutorials - Herong's Tutorial Examples** - v1.00, by Dr. Herong Yang

Python Program for Integer Elliptic Curves

This section provides simple Python program, IntegerEllipticCurve.py, that searches integer points on any given elliptic curve with integer coefficients.

If you are interested to find the element set of elliptic curve points in 2-dimensional integer space, here is my simple Python program, IntegerEllipticCurve.py, that searches integer points on any given elliptic curve with integer coefficients:

# IntegerEllipticCurve.py # Copyright (c) 2018, HerongYang.com, All Rights Reserved. # import sys if (len(sys.argv) < 3): print("Usage: python IntegerEllipticCurve.py a b") exit() aa = sys.argv[1] bb = sys.argv[2] a = int(aa) b = int(bb) r = 4*a**3 + 27*b**2 if (r == 0): print("Error: (a, b) = ("+aa+", "+bb+") and 4a^3 + 27b^2 == 0") exit() print("Elliptic equation: y^2 = x^3 + ax + b with (a, b) = (" +aa+", "+bb+")") # Find a x such that x^3 + ax + b < 0 x = 0 r = x**3 + a*x + b while (r >= 0): x = x - 1 r = x**3 + a*x + b print("Starting with: x = "+str(x)) # Find a x such that x^3 + ax + b >= 0 while ( r<0 ): x = x + 1 r = x**3 + a*x + b print("First condidate: x = "+str(x)) # Check every x < 100000 y = 0 while (x < 100000): r = x**3 + a*x + b l = y**2 while (l < r): y = y + 1 l = y**2 # print("(x, y) = ("+str(x)+", "+str(y)+")") # print("(r, l) = ("+str(r)+", "+str(l)+")") if (l == r): print("Point on curve: (x, y) = ("+str(x)+", "+str(y)+")") x = x + 1 print("Ended with (x, y, r, l) = " +str(x)+", "+str(y)+", "+str(r)+", "+str(l)+")") exit()

If you run it with (a,b) = (1,4), you will get:

C:\herong> python IntegerEllipticCurve 1 4 Elliptic equation: y^2 = x^3 + ax + b with (a, b) = (1, 4) Starting with: x = -2 First condidate: x = -1 Point on curve: (x, y) = (0, 2) Point on curve: (x, y) = (0, -2) Point on curve: (x, y) = (4128, 265222) Point on curve: (x, y) = (4128, -265222) Ended with (x, y, r, l) = 100000, 31622303, 999970000400002, 999970047023809)

The program works and found 4 points in the range of (x,y) < (1000000, 31622303):

(x, y) = (0, 2) (x, y) = (0, -2) (x, y) = (4128, 265222) (x, y) = (4128, -265222)

Of course, you can increase the search range to a higher number. But the program may crash with integer overflow exceptions or run for a long long time.

Table of Contents

Geometric Introduction to Elliptic Curves

Algebraic Introduction to Elliptic Curves

Abelian Group and Elliptic Curves

Discrete Logarithm Problem (DLP)

Generators and Cyclic Subgroups

►Reduced Elliptic Curve Groups

Converting Elliptic Curve Groups

Elliptic Curves in Integer Space

►Python Program for Integer Elliptic Curves

Elliptic Curves Reduced by Modular Arithmetic

Python Program for Reduced Elliptic Curves

Point Pattern of Reduced Elliptic Curves

Integer Points of First Region as Element Set

Reduced Point Additive Operation

Modular Arithmetic Reduction on Rational Numbers

Reduced Point Additive Operation Improved

What Is Reduced Elliptic Curve Group

Reduced Elliptic Curve Group - E23(1,4)

Reduced Elliptic Curve Group - E97(-1,1)

Reduced Elliptic Curve Group - E127(-1,3)

Reduced Elliptic Curve Group - E1931(443,1045)

Finite Elliptic Curve Group, Eq(a,b), q = p^n

tinyec - Python Library for ECC

ECDH (Elliptic Curve Diffie-Hellman) Key Exchange

ECDSA (Elliptic Curve Digital Signature Algorithm)