This is a security mechanism of the Symbian system. Generally, commonly used software has signed certificates, such as mobile QQ and so on. There is no problem in installing it. If the software written by an individual is not signed by a signing certificate, a Symbian authorization certificate is required. Baidu Mobile Home, enter the mobile phone certificate application page, enter the IMEI code of your mobile phone, and you will get a certificate exclusive to your mobile phone in about 2 hours. Use this certificate to sign the software that requires a certificate before it can be installed. . However, the Symbian system has come to an end, and even Nokia, which uses Symbian the most, has given up. There is no future in buying mobile phones with Symbian system now.