def calculate_signature key, string_to_sign
      hmac = HMAC::SHA1.new(key)
      hmac.update(string_to_sign)
      signature = Base64.encode64(hmac.digest).gsub("\n", '')
      if $DEBUG
        puts "Signature #{signature}"
      end
      signature
    end
def calculate_signature key, string_to_sign
      hmac = HMAC::SHA1.new(key)
      hmac.update(string_to_sign)
      signature = Base64.encode64(hmac.digest).gsub("\n", '')
      if $DEBUG
        puts "Signature #{signature}"
      end
      signature
    end
calculate the signature