Cydia

Cydia (/ˈsɪdiə/) is a package manager mobile app for iOS that enables a user to find and install software not authorized by Apple on jailbroken iPhones, iPads and iPod touch devices. It also refers to digital distribution platform for software on iOS accessed through Cydia software. Many of the software packages available through Cydia are free of charge, although some require purchasing. Cydia (/ˈsɪdiə/) is a package manager mobile app for iOS that enables a user to find and install software not authorized by Apple on jailbroken iPhones, iPads and iPod touch devices. It also refers to digital distribution platform for software on iOS accessed through Cydia software. Many of the software packages available through Cydia are free of charge, although some require purchasing. Cydia is developed by Jay Freeman (also called 'saurik') and his company, SaurikIT. The name 'Cydia' is a reference to the moth genus Cydia, notably the codling moth (with a scientific name of Cydia pomonella), which is the proverbial 'worm in the apple.' Cydia provides graphical user interface (GUI) to jailbroken users using Advanced Packaging Tool (APT) repositories to install software unavailable on the App Store. Cydia is based on APT, ported to iOS as part of Jay Freeman's Telesphoreo project. Software packages are downloaded directly to the iOS device. Apps are installed in the same location as Apple's own applications, the /Applications directory. Jailbroken devices can also still buy and download apps normally from the official App Store. Most Jailbreaking tools (each of them supporting a specific set of devices and iOS versions) install Cydia automatically, while others provide a choice to the user. Some of the packages available through Cydia are standard applications, while most packages are extensions and modifications for the iOS interface and for apps in the iOS ecosystem. Some apps available on Cydia are also emulators able to run images of games for old game consoles, albeit without those consoles' responsive controllers. Cydia enables users to find and install open source packages as well as purchase modifications for jailbroken iPhones. These modifications are based on a framework called Cydia Substrate (formally MobileSubstrate), which makes it relatively easy to install and update said modifications. UNIX command line tools are available on Cydia as well, including bash, coreutils and OpenSSH, meaning the device could potentially be used as a full-fledged UNIX workstation, although without many development tools. In March 2009, the now-defunct blog TUAW (The Unofficial Apple Weblog) announced that the Cydia Store, the in-app software purchasing system for Cydia, had opened for sales. The announcement also mentioned that Amazon payments was the only option available, but that PayPal would be added in the future, which it was. Cydia stopped accepting Amazon Payments in 2015, leaving PayPal as the sole payment option. After a bug related to PayPal digital token authorization was discovered which affected 'very few users,” via TechCrunch, Freeman decided to shut down the Cydia Store on December 16, 2018. Cydia caches the digital signatures called SHSH blobs used by Apple to verify restores of iOS (which Apple uses to limit users to only installing the latest version of iOS). Cydia's storage mechanism enables users to downgrade a device to a prior version of iOS by means of a replay attack. This means, for example, that a person with a jailbroken device who upgrades to a non-jailbreakable version of iOS can choose to downgrade back to a jailbreakable version. iOS 5.0 and later versions of iOS implement an addition to the SHSH system, a random number (a cryptographic nonce) in the 'APTicket', making it more difficult to perform a replay attack, and thus more difficult to downgrade.