Your 6300 is the third edition of Nokia Symbian intelligent operating system. Due to the copyright protection of Symbian system, when installing and using some software, it is necessary to sign the software before using it. The so-called signature is to apply for a certificate with the IMEI number of your mobile phone, and bind your certificate with the software that needs to be signed by the signing software, so that your software can be installed and used on your mobile phone. Press "*#06#" on the mobile phone to check the IMEI number of the mobile phone, and one IMEI number corresponds to a unique certificate. You can go now.

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You need to register before applying for a certificate. After getting the certificate, download a signed software and the corresponding key, and sign the software you want to install that needs to be signed. After signing, the software can be installed normally.