If the certificate expires, you can try to adjust the date with your mobile phone for half a year or more, and then try to install it. Unable to check the validity of the certificate online. Select all in Tools-Program Management-Settings-Software Installation, and check the online certificate. The issue of certificate, that is, the related rights of mobile phones. If there is no certificate signature, some software can't be trusted, which indicates that the certificate is wrong, expired or any file is damaged, and it can't be installed. Certificate is to give some untrustworthy software, that is, the machine is untrustworthy and cannot be installed normally. Signature and signature tools are used together to generate a self-signed software. It's a little different from the previous original software. Of course, it doesn't mean that mobile phones can't install software without certificates. Some popular ones can be installed directly, and those are included in trust software, such as QQ and UCWEB. The following website can download signature tools and have tutorials. This was signed directly on the mobile phone. /signtool.php suggests that you crack the permissions of the mobile phone, so that the installation files will not be restricted by the certificate in the future, and you can also view and modify the contents of the C drive. After the crack, I didn't feel anything wrong. There is an article "The conclusion of whether to crack the mobile phone". You can read and submit your serial number (displayed by *#06#) and your mobile phone model and email address at /cer Hong Fei Mobile http://61.143.251.83/. Apply for an account in the forum first, and registration is very simple. Again, the certificate is not directly installed on the mobile phone, but used in conjunction with the signature tool. Whether the certificate is in the card or in the computer depends on the person. It is recommended to back it up elsewhere in case it is lost. In addition, I would like to remind you that even with the certificate, some signed software cannot be installed, and this problem will not occur after being cracked. I use n73. I have applied for a certificate before, but I can't. Some self-signed software still cannot be installed. Now it's cracked, and this problem has never appeared again. There is also someone who gives you a certificate, all of which are applied to major forums. There are experts, but there are few who can really do it and have conditions. According to the earliest certificate making, it costs several thousand yuan to buy a certificate making software. Anyone who has so much money to buy this thing will be bored, and it should not be cheap now. There are only those big forums. Submit your serial number (displayed by *#06#), and I can help you apply for the certificate. I will give it to you today. . .