47CertificatesImportant: Even if the use of certificates makes the risks involved in remoteconnections and software installation considerably smaller, they must be usedcorrectly in order to benefit from increased security.The existence of a certificate does not offer any protection by itself; the certificate managermust contain correct, authentic, or trusted certificates for increased security to be available.Certificates have a restricted lifetime. If "Expired certificate" or "Certificate not valid yet" isshown even if the certificate should be valid, check that the current date and time in yourdevice are correct.Before changing any certificate settings, you must make sure that you really trust the ownerof the certificate and that the certificate really belongs to the listed owner.There are three kinds of certificates: server certificates, authority certificates, and usercertificates. You may receive these certificates from your service provider. Authority certificatesand user certificates may also be saved in the security module by the service provider.To view the list of the authority or user certificates downloaded into your phone, selectMenu > Settings > Security > Authority certificates or User certificates.is displayed during a connection, if the data transmission between the phone and thecontent server is encrypted.The security icon does not indicate that the data transmission between the gateway andthe content server (or place where the requested resource is stored) is secure. The serviceprovider secures the data transmission between the gateway and the content server.Digital signatureYou can make digital signatures with your phone if your SIM card has a security module.Using the digital signature can be the same as signing your name to a paper bill, contract,or other document.To make a digital signature, select a link on a page, for example, the title of the book youwant to buy and its price. The text to sign, which may include the amount and date, is shown.Check that the header text is Read and that the digital signature icon is shown.Note: If the digital signature icon does not appear, there is a security breach, andyou should not enter any personal data such as your signing PIN.To sign the text, read all of the text first, and select Sign.The text may not fit within a single screen. Therefore, make sure to scroll through and readall of the text before signing.Select the user certificate you want to use. Enter the signing PIN. The digital signature icondisappears, and the service may display a confirmation of your purchase.