Windows

1. Open PowerShell, and navigate to the IPSW file that you downloaded, e.g. cd Downloads
2. Type Get-FileHash iPhone_5.5_P3_11.0_11.4_15F79_Restore.ipsw -Algorithm SHA1
3. The output of the command should match the following checksum: b424df080797b216539cc47e6c67dca18da608cd. If it doesn't, you may need to redownload the file.

macOS

1. Open a terminal, and navigate to the IPSW file that you downloaded, e.g. cd ~/Downloads
2. Type openssl sha1 iPhone_5.5_P3_11.0_11.4_15F79_Restore.ipsw
3. The output of the command should match the following checksum: b424df080797b216539cc47e6c67dca18da608cd. If it doesn't, you may need to redownload the file.

Linux

1. Open a terminal, and navigate to the IPSW file that you downloaded, e.g. cd ~/Downloads
2. Type openssl sha1 iPhone_5.5_P3_11.0_11.4_15F79_Restore.ipsw
3. The output of the command should match the following checksum: b424df080797b216539cc47e6c67dca18da608cd. If it doesn't, you may need to redownload the file.

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Checksums

SHA256sum	4613961f3e4cb8b3df887fca671517eb0e111714623707ea75dee8adee41a39d
MD5sum	4cb9e2aa3c545c4a10a0387d293b1365
SHA1sum	b424df080797b216539cc47e6c67dca18da608cd

Please note, the documentation below is supplied from Apple's update servers. We don't modify the contents of this documentation.

iOS 11.4 includes AirPlay 2 multi-room audio, support for HomePod stereo pairs, and Messages in iCloud. This update also includes bug fixes and improvements.

AirPlay 2

• Control your home audio system and AirPlay 2-enabled speakers throughout your house
• Play music at the same time on multiple AirPlay 2-enabled speakers in your house, all in sync
• Control AirPlay 2-enabled speakers from Control Center, the Lock screen, or AirPlay controls within apps on your iPhone or iPad
• Use your voice to control AirPlay 2-enabled speakers with Siri from your iPhone or iPad, HomePod, or Apple TV
• Take a call or play a game on your iPhone or iPad without interrupting playback on your AirPlay 2-enabled speakers

HomePod stereo pair

• This update supports setting up your HomePod stereo pair using your iPhone or iPad
• HomePod pair automatically senses its location in the room and balances the sound based on the speakers' locations
• Advanced beamforming provides wider soundstage than traditional stereo pair
• HomePod will automatically update to support stereo pairs, unless auto updates are disabled in the Home app

Messages in iCloud

• Store your messages, photos, and other attachments in iCloud and free up space on your devices
• All your messages appear when you sign into a new device with the same iMessage account
• When you delete messages and conversations they are instantly removed from all your devices
• To turn on Messages in iCloud, enable Messages in iCloud settings (Settings > [your name] > iCloud)
• Your conversations continue to be end-to-end encrypted

Other improvements and fixes

• Enables teachers to assign their students reading activities in iBooks using the Schoolwork app
• Fixes an issue where certain character sequences could cause Messages to crash
• Addresses a Messages issue that could cause some messages to appear out of order
• Addresses an issue that could prevent logging in or accessing files on Google Drive, Google Docs and Gmail in Safari
• Fixes an issue that could prevent data syncing in Health
• Fixes an issue that could prevent users from changing what apps can access Health data
• Resolves an issue that could cause an app to appear in an incorrect location on the Home screen
• Fixes an issue where CarPlay audio could become distorted
• Fixes an issue where selecting music from your iPhone could fail when playing music over Bluetooth or when connected to USB on some vehicles

For information on the security content of Apple software updates, please visit this website:

https://support.apple.com/kb/HT201222