https://github.com/hellman/libnum
Working with numbers (primes, modular, etc.)
https://github.com/hellman/libnum
Last synced: 5 months ago
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Working with numbers (primes, modular, etc.)
- Host: GitHub
- URL: https://github.com/hellman/libnum
- Owner: hellman
- Created: 2011-08-15T08:49:36.000Z (over 14 years ago)
- Default Branch: master
- Last Pushed: 2022-07-15T20:32:37.000Z (over 3 years ago)
- Last Synced: 2025-04-04T11:05:52.471Z (11 months ago)
- Language: Python
- Homepage:
- Size: 80.1 KB
- Stars: 241
- Watchers: 16
- Forks: 60
- Open Issues: 3
-
Metadata Files:
- Readme: README.md
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README
# libnum
This is a python library for some numbers functions:
* working with primes (generating, primality tests)
* common maths (gcd, lcm, n'th root)
* modular arithmetics (inverse, Jacobi symbol, square root, solve CRT)
* converting strings to numbers or binary strings
Library may be used for learning/experimenting/research purposes. Should NOT be used for secure crypto implementations.
## Installation
```bash
$ pip install libnum
```
Note that only Python 3 version is maintained.
## Development
For development or building this repository, [poetry](https://python-poetry.org/) is needed.
Tests can be ran with
```bash
$ pytest --doctest-modules .
```
## List of functions
Common maths
* len\_in\_bits(n) - number of bits in binary representation of @n
* randint\_bits(size) - random number with a given bit size
* extract\_prime\_power(a, p) - s,t such that a = p**s * t
* nroot(x, n) - truncated n'th root of x
* gcd(a, b, ...) - greatest common divisor of all arguments
* lcm(a, b, ...) - least common multiplier of all arguments
* xgcd(a, b) - Extented Euclid GCD algorithm, returns (x, y, g) : a * x + b * y = gcd(a, b) = g
Modular
* has\_invmod(a, n) - checks if a has modulo inverse
* invmod(a, n) - modulo inverse
* solve\_crt(remainders, modules) - solve Chinese Remainder Theoreme
* factorial\_mod(n, factors) - compute factorial modulo composite number, needs factorization
* nCk\_mod(n, k, factors) - compute combinations number modulo composite number, needs factorization
* nCk\_mod\_prime\_power(n, k, p, e) - compute combinations number modulo prime power
Modular square roots
* jacobi(a, b) - Jacobi symbol
* has\_sqrtmod\_prime\_power(a, p, k) - checks if a number has modular square root, modulus is p**k
* sqrtmod\_prime\_power(a, p, k) - modular square root by p**k
* has\_sqrtmod(a, factors) - checks if a composite number has modular square root, needs factorization
* sqrtmod(a, factors) - modular square root by a composite modulus, needs factorization
Primes
* primes(n) - list of primes not greater than @n, slow method
* generate\_prime(size, k=25) - generates a pseudo-prime with @size bits length. @k is a number of tests.
* generate\_prime\_from\_string(s, size=None, k=25) - generate a pseudo-prime starting with @s in string representation
Factorization
* is\_power(n) - check if @n is p**k, k >= 2: return (p, k) or False
* factorize(n) - factorize @n (currently with rho-Pollard method)
warning: format of factorization is now dict like {p1: e1, p2: e2, ...}
ECC
* Curve(a, b, p, g, order, cofactor, seed) - class for representing elliptic curve. Methods:
* .is\_null(p) - checks if point is null
* .is\_opposite(p1, p2) - checks if 2 points are opposite
* .check(p) - checks if point is on the curve
* .check\_x(x) - checks if there are points with given x on the curve (and returns them if any)
* .find\_points\_in\_range(start, end) - list of points in range of x coordinate
* .find\_points\_rand(count) - list of count random points
* .add(p1, p2) - p1 + p2 on elliptic curve
* .power(p, n) - n✕P or (P + P + ... + P) n times
* .generate(n) - n✕G
* .get\_order(p, limit) - slow method, trying to determine order of p; limit is max order to try
Converting
* s2n(s) - packed string to number
* n2s(n) - number to packed string
* s2b(s) - packed string to binary string
* b2s(b) - binary string to packed string
Stuff
* grey\_code(n) - number in Grey code
* rev\_grey\_code(g) - number from Grey code
* nCk(n, k) - number of combinations
* factorial(n) - factorial
## About
Author: hellman
License: [MIT License](http://opensource.org/licenses/MIT)