Python public-key cryptography example

Simpliest as possible implementation of asymmetric encryption with Public-key in Python. Something like RSA, but easier and clearer.

Python's built-in math functions are not used for clarity.

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Except for basic operators:
Floor Division
Modulo Division
Exponent
Bitwise Operators
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Implemented functions:

• Binary search to find floor square root of positive integer
• Modular exponentiation by repeated squaring for fast computation of large positive integer powers of a number
• Euclidean algorithm for computing the greatest common divisor (GCD) of two numbers
• Extended Euclidean algorithm that computes coefficients of Bézout's identity to find Private-key exponent (modular multiplicative inverse of Public-key exponent)
• Trial division (easiest to understand of the integer factorization algorithms) to determine whether a number is a prime
• Fermat primality test to check it exponentially faster way

Large messages are splitts into blocks.