The Kekz Headphones operate using small chips called “Kekz” or “Cookies” to play audio stories stored on the device itself. The headphones contain an SD card with encrypted files, making access challenging. Through reverse engineering efforts, it was discovered that a string on the NFC chip contained essential information for playing content. By manipulating this string, cookies could be cloned, allowing access to content previously unseen. An encryption routine used to convert MP3 files to the kez format was analyzed, leading to the development of a method to decrypt the headphone’s content. Additionally, an application named “Kekzmonster” was created for NFC communication with the headphones.
https://nv1t.github.io/blog/kekz-headphones/