There is a universal phenomenon that people often ask what certificate is when they use the third edition of Symbian S60 at their first time. What is the signature? Why we need it? What is the difference? Because there are different restrictions of grade and competence for different kinds of Certificates. The lowest grade of certificate can only be used to install ordinary game, theme, general application software. Such certificates can be closed through the setting option of certificate inspection (steps: Menu button–Applications–process management– options – set up, software installation option “ All” , on-line certificate inspection option “Off”) to circumvent the certificate and access to the installation.
Next ,we will introduce  some detail information about the S60 3rd certificate. Hope that will be helpful.

1: What is a certificate?
Certificate is the license of software installation. When you install a software, The system of Nokia S60 3rd will analysis whether you have a license for the software that you just want to install, if not, this installation will be prohibited by the system.   
There are different restrictions of grade and competence for different kinds of Certificates. The lowest grade of certificate can only be used to install ordinary game, theme, general application software. Such certificates can be closed through the setting option of certificate inspection (steps: Menu button – Applications – process management – options – set up, software installation option “ All” , on-line certificate inspection option “Off”) to circumvent the certificate and access to the installation. Since the default setting is check-off , so that is why there are a lot of common software can install without a license. Slightly higher – grade certificate will allow the software information enters C – system folder of the mobile phone、modify system parameters、at present this kind of certificate domain the signed certificated area.     The highest authority certificate can modify system, but have to pay from Nokia.

2: What is the role of the certificate?
In order to improve security system.  As we all know, virus attack because he can sneak into your system without your authority, and operate automatically, calling procedures, modify system files and run automatically while booting, then double their own reproduction in different transmission between computers, unable to extricate. But these virus can’t implement under S60 3rd , just because this Certificate Validation mechanism.  
Even the virus producer uses the low – grade certificate. His virus can be planted into your system. But because of lacking authority, he can not launch the virus, call system documents and procedures, and spread the virus to other phones, so this virus is equivalent to waste.  In order to obtain a higher authority, only if this software let you sign to him, first the virus have to pass your check, If you really has signed for a virus, then virus's harm is also smallest. Because the certificate is exclusively corresponsive to your unique IMEI Code of your mobile phone, there is no possibility that the virus can spread without proliferating. So we have no idea how Viral maker benefits from his virus.  One thing could be sure is that the viral maker obtains the highest jurisdiction certificate to be able to realize the evil purpose. But how Nokia may grant a certificate for a virus maker?  If only the highest jurisdiction certificate has been decoded by the hacker. Such kind of thing has never happened before. Judging from the current situation, the antivirus software of S60 3rd has not been fully utilized yet. 

3: How to obtain the certificate?
Ordinary users need to register an account through the Symbian net to obtain the second kind of certificate. Then provide your own code application, and obtain a certificate document which will only be suitable for your mobile phone.  Now web of symbian restrict people seriously to register domain names ( i.e. the @ following part) of Email. We can register only a few accounts with the same e-mail domain name.  Now only those rarely seen by the public or external e-mail domain name could be registered successfully.   Therefore, the majority of people are required to provide their own string of phone, and seek help from their net friends who already have a account to create a certificate.  If you want to make a certificate on your own, you can consult the relevant book.
Certificate is exclusively corresponding to your string of phone, therefore the certificate cannot use in common. Your certificate can be used in your mobile phone only, which means you can sign your software which you want to install to your phone with your own certificate as much as you want. But you cannot use your certificate to sign for others, then install these software which have been signed to other’s handset.

4: Do certificate have the term of validity? 
Yes, they do have. The new certificate term of validity which applies from December 2007 is three years, the certificate term of validity before are all half year.  After the expiration, software which has been installed will operate as usual, the only impact is that when you use this expired certificate to sign anther software, then when you install this software, the system of S60 3rd will prompt the certificate time error and will not allow to install.  Solution: Either you go to the symbian net to apply for a certificate again, or you just adjust the time of your handset to an arbitrary period of time that is valid to use your certificate, then sign with your original certificate, adjust your phone time to normal after finishing installation.  Present’s certificate term of validity is long enough for us to use, just some software which had been decoded by the signature before are already expired, this kind of software can be used again by eliminating the old signature and sign new one.

5: what is a signature? How to sign? 
Signature is binding the certificate you have already applied to those installation procedure which need signature software, so make this installation procedure pass the inspection of S60 3rd. Actually this is a pack process.
There are several method to bind through computer operation, the most commonly one is carrying on binding through the special signature software. There are something needed to be mentioned here. In the process of the certificate is required to provide a key documents and certificates counterparty (another authentication mechanism).
When you signing, three options are prerequisite, key document、certificate and the software waiting for signing, but now almost all the production of certificate using the same key document. Therefore some signature software do not appoint key document when user sign their software.

The S60 certificate expert (delight intelligent version) is such kind of useful software which does not need to be assigned key document. The surface of this software is easy – to – understand, there is no necessary of special introduction, as long as assign the certificate under the software signature window and waiting for the signature to run later. 
Signsis is the signature software which operate in a handset, this software needs document key, when signature what needs to pay attention is must choose “the signature”, do not choose “from the signature”, because the jurisdiction is lower to “from the signature” . There will be a “X” after the suffix of the name of generated document, this “X” could be deleted, but it will not effect whether you remain it or not.
Some users may meet this kind of situation that the certificate does not work, in most of cases because there I something wrong with your strings or certificate with their string of phone do not correspond. Of course, we can not rule out that the producer has revised the certificate. It also could be the reason that the producer’s key is not general. 

6: What kind of software requires signature?
Currently those big companies or some which really need these signatures will purchase senior authority certificate from Nokia Corporation. Commonly by some secure manufacturers. So their software needn’t our signature at all.  There are also many ordinary internet applications, irrelevance with the system, with low authority, no danger, such as network TV software, reading software, QQ, theme, all of them are no need of signature.Those software required signature van be broadly classified into the following types:
(1):  Staring with the boot, such as CallMaster, ZT-A4;
(2):  Running automatically without your operation, such as screensaver producer;
(3):  Accessing to the system folder and amend, and so on.

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Tags：certificate, nokia, s60 3rd, signature, symbian OS.
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