138Copyright © 2005 Nokia. All rights reserved.Important: Note that even if the use of certificates makes the risks involved inremote connections and software installation considerably smaller, they must beused correctly in order to benefit from increased security. The existence of acertificate does not offer any protection by itself; the certificate manager mustcontain correct, authentic, or trusted certificates for increased security to beavailable. Certificates have a restricted lifetime. If Expired certificate or Certificatenot valid yet is shown even if the certificate should be valid, check that the currentdate and time in your device are correct.Before changing any certificate settings, you must make sure that you really trustthe owner of the certificate and that the certificate really belongs to the listedowner.Digital signatureYou can make digital signatures with your phone if your SIM card has a securitymodule. The signature can be traced back to you via the private key on the securitymodule and the user certificate that was used to perform the signature. Using thedigital signature can be the same as signing your name to a paper bill, contract orother document.To make a digital signature, select a link on a page, for example, the title of thebook that you want to buy and its price. The text to sign (possibly includingamount, date, etc.) will be shown.Check that the header text is Read and that the digital signature icon isshown.Note: If the digital signature icon does not appear, there is a securitybreach, and you should not enter any personal data such as your signingPIN.
