Symbian has had an added security measure built into OS v9.x phones which required you to sign your Symbian applications before installing them. Only applications and games from trusted developers are pre-signed so that you can install them directly. Everything else has to be signed before installation.
To start signing your Symbian OS9 applications, you first need to get a certificate for your Symbian phone and then sign it using SignSIS.
How to get a Signing Certificate for your Symbian phone
There are two ways to get a signing certificate.
1st method
Just go to http://cer.opda.cn/en and register as a user. Enter your IMEI and you should get a certificate in 10-12 hours.
2nd method
Go to http://cer.s603rd.cn and enter your IMEI and the verification code in the two boxes. The certificate should be generated in 10-12 hours. Just visit the site again and enter your IMEI again to download your certificate.
How to Sign your Symbian Applications using SignSIS
Once you have your certificate, you can sign applications using the SignSIS tool.
Download SignSIS here
Extract the files from the zip archive using WinRAR or WinZip and run SignTool.exe
In the boxes with the chinese text:
#1 Browse and select the SignSIS.exe file
#2 Select the unsigned SIS file
#3 Select the .CER certificate
#4 Select the .KEY key
#5 Browse and select the unsigned SIS file but rename it to something else. This is where the signed file will be saved.