How to resolve the algorithm Bitcoin/address validation step by step in the Mathematica / Wolfram Language programming language

Published on 22 June 2024 08:30 PM

How to resolve the algorithm Bitcoin/address validation step by step in the Mathematica / Wolfram Language programming language

Table of Contents

Problem Statement

Write a program that takes a bitcoin address as argument, and checks whether or not this address is valid. A bitcoin address uses a base58 encoding, which uses an alphabet of the characters 0 .. 9, A ..Z, a .. z, but without the four characters:

With this encoding, a bitcoin address encodes 25 bytes:

To check the bitcoin address, you must read the first twenty-one bytes, compute the checksum, and check that it corresponds to the last four bytes. The program can either return a boolean value or throw an exception when not valid. You can use a digest library for SHA-256.

It doesn't belong to anyone and is part of the test suite of the bitcoin software.
You can change a few characters in this string and check that it'll fail the test.

Let's start with the solution:

Step by Step solution about How to resolve the algorithm Bitcoin/address validation step by step in the Mathematica / Wolfram Language programming language

Purpose: The provided Wolfram code is an implementation of a hashing algorithm for converting an input string into a 32-byte hashed value. It operates on the principle of converting an input string to a sequence of integers, hashing that sequence twice using SHA256, and extracting the first 32 bytes of the double-hashed result as the final hash.

Detailed Explanation:

Step 1: Character Conversion

  • The chars variable contains a string of characters from '1' to 'z' (excluding 'I', 'l', and 'O').
  • For each character in the input string, the StringPosition function finds its position in the chars string.
  • The position is decremented by 1 to produce an integer value between 0 and 61.

Step 2: Integer Digits

  • The list of integer values generated in Step 1 is converted to a base-58 integer using IntegerDigits.

Step 3: First Hash

  • The base-58 integer is converted back to a string using FromDigits.
  • The resulting string is hashed using the SHA256 algorithm with a 256-bit output size.

Step 4: Second Hash

  • The first 32-bit (4-byte) portion of the first hash is converted to a string.
  • The string is hashed again using SHA256.

Step 5: Final Hash

  • The first 32-bit portion of the second hash is extracted. This is the final hash result.

Step 6: Comparison

  • The final 32-bit hash result is compared to the 32-bit hash calculated from the first 32-bit portion of the first hash. They should be equal if the algorithm is working correctly.

Note:

  • The purpose of excluding 'I', 'l', and 'O' in the chars string is to avoid confusion with '1', '0', and 'l' in the output string.
  • The choice of a base-58 integer representation is arbitrary and could be replaced with other base representations.
  • The use of double hashing with SHA256 is for increased security by reducing the likelihood of hash collisions.

Source code in the wolfram programming language

chars = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"; data = 
 IntegerDigits[
  FromDigits[
   StringPosition[chars, #][[1]] - 1 & /@ Characters[InputString[]], 
   58], 256, 25];
data[[-4 ;;]] == 
 IntegerDigits[
   Hash[FromCharacterCode[
     IntegerDigits[Hash[FromCharacterCode[data[[;; -5]]], "SHA256"], 
      256, 32]], "SHA256"], 256, 32][[;; 4]]


  

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