Understanding proof-of-work using Ruby - https://blog.robertsj.com/proof-of-work

proof_of_work.rb

class ProofOfWork
  require 'digest'

  def initialize(difficulty:)
    @required_number_of_zeros = difficulty
  end

  def find_nonce_for(block_content:)
    nonce = 0

    until found_correct_nonce?(nonce, block_content)
      nonce += 1
    end

    nonce
  end

  private

  attr_reader :required_number_of_zeros

  def hash(block_content_and_nonce)
    Digest::SHA256.hexdigest(block_content_and_nonce)
  end

  def found_correct_nonce?(nonce, block_content)
    hash(block_content + nonce.to_s).start_with? required_number_of_zeros
  end
end

worker = ProofOfWork.new(difficulty: "00000")
nonce = worker.find_nonce_for(block_content: "hello world!")