You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: crypto.rb
    path of file: ./repos/mashcard/apps/server-monolith/lib/mashcard
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

module Mashcard
  module Crypto
    PREFIX = 'CYPHERPUNK'
    SUBKEY_MAPPING = {
      hash_salt: 1,
      data_encr
    
      def root_key
        @root_key ||= begin
          seed = ENV['SECRET_KEY_SEED']
          raise 'SECRET_KEY_SEED is not set' if seed.blank?

          raw = Utils::Encoding::Base64.strict_decode64(seed)
          # Use Google Cloud KMS to decrypt the seed if it's available
          ENV['GCP_KMS_FRN'].present? ? gcp_kms_decrypt(raw) : raw
        end