When you purchase a Nokia 6131 NFC mobile phone, the phone’s secure element contains secret, chip specific keys for Card Manager authentication and management of the secure element as in GlobalPlatform 2.1.1. Nokia NFC Unlock Service MIDlet connects to a server and the connection is used to add a new set of authentication keys to keyset version 42 with the ENC, MAC and DEK keys having the value 404142434445464748494A4B4C4D4E4F.
Nokia NFC Unlock Service MIDlet unlocks the secure element permanently. After this operation the secure element on the device may no longer be considered secure by third party application issuers. Consequently, the device may no longer be used for installing and running third party services that require a secure and trusted connection between the service provider and the secure element, such as payment cards and transport applications.
BE AWARE: Unlocking of the secure element can not be undone once it has been performed.
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More information about Nokia NFC Unlock Service MIDlet, refer to Forum Nokia Wiki Page: Nokia 6131 NFC - FAQs