Example Base58 Implementation (showing haxx0r> on #ruby irc)

base58.rb

module Base58
  CHARACTERS = [*?1..?9, *?a..?k, *?m..?z, *?A..?H, *?J..?N, *?P..?Z].freeze

  module_function

  def encode(n)
    chars = []

    while n >= 58
      chars.unshift CHARACTERS[n % 58]
      n -= n % 58
      n /= 58
    end

    chars.unshift CHARACTERS[n]

    chars.join
  end
end

BASE58_CHARACTERS = '123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ' might also do the job? No need for it to be an array?