EC Cryptography Tutorials - Herong's Tutorial Examples - v1.02, by Dr. Herong Yang
What Is Hasse's Theorem
This section describes Hasse's Theorem, which states that the order, n, of a reduced elliptic curve group, Ep(a,b), is bounded in the range of [p+1 - 2*sqrt(p), p+1 + 2*sqrt(p)].
What Is Hasse's Theorem? Hasse's Theorem is also called Hasse Bound, which provides an estimate of the number of points on an elliptic curve over a finite field, bounding the value both above and below.
For a given elliptic curve E(a,b) over a finite field with q elements, the number of points, n, on the curve satisfies the following condition: |n - (q+1)| <= 2*sqrt(q)
If we apply Hasse's Theorem to our reduced elliptic curve group definition, Ep(a,b)), we have:
Given reduced elliptic curve group Ep(a,b), the group order, n, satisfies the following condition: |n - (p+1)| <= 2*sqrt(p) Or n is in a range as expressed below: p+1 - 2*sqrt(p) <= n <= p+1 + 2*sqrt(p)
It's interesting to see that the group order is only depending on the prime number used in the modular arithmetic reduction, not on coefficients, a and b, of the elliptic curve equation.
Hasse's Theorem is named after German mathematician Helmut Hasse (25 August 1898 - 26 December 1979):
For more details, see "Hasse's theorem on elliptic curves" at en.wikipedia.org/wiki/Hasse%27s_theorem_on_elliptic_curves.
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)