Decrypt string using openssl key and ruby

decrypt.rb

require 'openssl'
require 'base64'

private_key_file = 'privkey.pem';
password = 'this phrase is the clue to unlock the encryption'

encrypted_string = ""

File.open(ARGV[0]).each_line do |line|
   encrypted_string += line
end

private_key = OpenSSL::PKey::RSA.new(File.read(private_key_file),password)
string = private_key.private_decrypt(Base64.decode64(encrypted_string))
puts string