If you have a certificate, you still have to sign it. You can go to Saipan to download the free signature to help you complete the signature (it is best to make a certificate in Saipan first, this is omnipotent). The landlord can also choose to crack the phone. The tutorial is actually very simple, which solves the trouble of signing a contract from now on, but you should be careful, because some software is malicious and I hope it will help the landlord.