IPSW, iPhone Software, is a file format used to install

iOS iOS (formerly iPhone OS) is a mobile operating system created and developed by Apple Inc. exclusively for its hardware. It is the operating system that powers many of the company's mobile devices, including the iPhone; the term also include ...

iPadOS iPadOS is a mobile operating system developed by Apple Inc. for its iPad line of tablet computers. It is a rebranded variant of iOS, the operating system used by Apple's iPhones, renamed to reflect the diverging features of the two product ...

tvOS tvOS (formerly known as Apple TV Software) is an operating system developed by Apple Inc. for the Apple TV, a digital media player. In the first-generation Apple TV, Apple TV Software was based on Mac OS X. Starting with the second-generation, ...

HomePod The HomePod is a smart speaker developed by Apple Inc. The HomePod was designed to work with the Apple Music subscription service. The HomePod was announced on June 5, 2017, at the Apple Worldwide Developers Conference. Its launch was later d ...

, and most recently,

macOS macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and lapt ...

firmware for devices equipped with

Apple silicon Apple silicon is a series of system on a chip (SoC) and system in a package (SiP) processors designed by Apple Inc., mainly using the ARM architecture. It is the basis of most new Mac computers as well as iPhone, iPad, iPod Touch, Apple TV, ...

. All

Apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple trees are cultivated worldwide and are the most widely grown species in the genus ''Malus''. The tree originated in Central Asia, where its wild ancestor, ' ...

devices share the same IPSW file format for

firmware and their derivatives, allowing users to

flash Flash, flashes, or FLASH may refer to: Arts, entertainment, and media Fictional aliases * Flash (DC Comics character), several DC Comics superheroes with super speed: ** Flash (Barry Allen) ** Flash (Jay Garrick) ** Wally West, the first Kid F ...

their devices through Finder or iTunes on

Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for ser ...

, respectively. Users can flash Apple silicon Macs through Apple Configurator 2.

Structure

The .ipsw file itself is a compressed

archive file In computing, an archive file is a computer file that is composed of one or more files along with metadata. Archive files are used to collect multiple data files together into a single file for easier portability and storage, or simply to compre ...

(renamed

Zip archive ZIP is an archive file format that supports lossless data compression. A ZIP file may contain one or more files or directories that may have been compressed. The ZIP file format permits a number of compression algorithms, though DEFLATE is th ...

) containing at least three

Apple Disk Image Apple Disk Image is a disk image format commonly used by the macOS operating system. When opened, an Apple Disk Image is mounted as a volume within the Finder. An Apple Disk Image can be structured according to one of several proprietary disk ...

files with one containing the root file system of the OS and two ram disks for restore and update.

, audioOS and

also include a disk image for the recovery environment (recoveryOS). The file also holds the kernel caches, and a "Firmware" folder which contains iBoot, LLB (Low-Level Bootloader), iBSS (iBoot Single Stage), iBEC (iBoot Epoch Change), the Secure Enclave Processor firmware, the Device Tree, Firmware Images (Apple logo, battery images, Recovery mode screen and more),

baseband In telecommunications and signal processing, baseband is the range of frequencies occupied by a signal that has not been modulated to higher frequencies. Baseband signals typically originate from transducers, converting some other variable int ...

firmware files in .bbfw format (renamed zip file), and other firmware files. There are two more files named "BuildManifest.plist" and "Restore.plist", both property lists that contain compatibility information and SHA-256 hashes for different components. BuildManifest.plist is sent to Apple's TSS server and checked in order to obtain SHSH blobs before every restore. Without SHSH blobs, the device will refuse to restore, thus making downgrades very difficult to achieve.

Security and rooting

The archive is not password-protected, but iBoot, LLB, iBEC, iBSS, iBootData and the Secure Enclave Processor firmware images inside it are encrypted with AES. Until

iOS 10 iOS 10 is the tenth major release of the iOS mobile operating system developed by Apple Inc., being the successor to iOS 9. It was announced at the company's Worldwide Developers Conference on June 13, 2016, and was released on September ...

, all the firmware files (including the root file system and Restore and Update ramdisks) were encrypted. While Apple does not release these keys, they can be extracted using different iBoot or

bootloader A bootloader, also spelled as boot loader or called boot manager and bootstrap loader, is a computer program that is responsible for booting a computer. When a computer is turned off, its softwareincluding operating systems, application code, an ...

exploits, such as limera1n (created by

George Hotz George Francis Hotz (born October 2, 1989), alias geohot, is an American security hacker, entrepreneur, and software engineer. He is known for developing iOS jailbreaks, reverse engineering the PlayStation 3, and for the subsequent lawsuit bro ...

, more commonly known as ''geohot''). Since then, many tools were created for the decryption and modification of the root file system.

Government data access

After the 2015 San Bernardino attack, the FBI recovered the shooter's

iPhone 5C The iPhone 5C (marketed as iPhone 5c) is a smartphone that was designed and marketed by Apple Inc. It is part of the sixth generation of the iPhone. The device was unveiled on September 10, 2013, and released on September 20, 2013, alon ...

, which belonged to the San Bernardino County Department of Public Health. The FBI recovered

iCloud iCloud is a cloud service from Apple Inc. launched on October 12, 2011 as a successor to MobileMe. , the service had an estimated 850 million users, up from 782 million users in 2016. iCloud enables users to sync their data to the cloud, inclu ...

backups from one and a half months before the shooting, and wanted to access encrypted files on the device. The U.S. government ordered Apple to produce an IPSW file that would allow investigators to brute force the passcode of the iPhone. The order used the

All Writs Act The All Writs Act is a United States federal statute, codified at , which authorizes the United States federal courts to "issue all writs necessary or appropriate in aid of their respective jurisdictions and agreeable to the usages and principles ...

, originally created by the Judiciary Act of 1789, to demand the firmware, in the same way as other smartphone manufacturers have been ordered to comply.

Tim Cook Timothy Donald Cook (born November 1, 1960) is an American business executive who has been the chief executive officer of Apple Inc. since 2011. Cook previously served as the company's chief operating officer under its co-founder Steve Jobs ...

responded on the company's webpage, outlining a need for encryption, and arguing that if they produce a

backdoor A back door is a door in the rear of a building. Back door may also refer to: Arts and media * Back Door (jazz trio), a British group * Porta dos Fundos (literally “Back Door” in Portuguese) Brazilian comedy YouTube channel. * Works so titl ...

for one device, it would inevitably be used to compromise the privacy of other iPhone users:

References

{{reflist, 30em

Structure

Security and rooting

Government data access

References

External links