![]() In either case, if the verification fails, the startup process halts and the user is prompted to reinstall macOS. On an Intel-based Mac with an Apple T2 Security Chip, the bootloader forwards the measurement and signature to the kernel, which then verifies the seal directly before mounting the root file system. On a Mac with Apple silicon, the bootloader verifies the seal before transferring control to the kernel. ![]() And because each node of the tree recursively verifies the integrity of the hashes of its children-similar to a binary hash (Merkle) tree-the root node’s hash value, called a seal, therefore encompasses every byte of data in the SSV, which means the cryptographic signature covers the entire system volume.ĭuring macOS installation and update, the seal is recomputed from the file system on-device and that measurement is verified against the measurement Apple signed. In case of mismatch, the system assumes the data has been tampered with and won’t return it to the requesting software.Įach SSV SHA256 hash is stored in the main file-system metadata tree, which is itself hashed. Data from the internal storage device (including file system metadata) is cryptographically hashed in the read path, and the hash is then compared with an expected value in the file-system metadata. ![]() SSV strengthens the integrity mechanism by adding cryptographic hashes, thus extending it to encompass every byte of file data. Since its introduction, APFS has provided file-system metadata integrity using noncryptographic checksums on the internal storage device. And because SSV uses APFS (Apple File System) snapshots, if an update can’t be performed, the old system version can be restored without reinstallation. SSV not only helps prevent tampering with any Apple software that’s part of the operating system, it also makes macOS software update more reliable and much safer. Starting in iOS 15 and iPadOS 15, the system volume on an iOS and iPadOS device also gains the cryptographic protection of a signed system volume. SSV features a kernel mechanism that verifies the integrity of the system content at runtime and rejects any data-code and noncode-without a valid cryptographic signature from Apple. macOS 11 or later adds strong cryptographic protections to system content with a signed system volume (SSV). In macOS 10.15, Apple introduced the read-only system volume, a dedicated, isolated volume for system content. Signed system volume security in iOS, iPadOS, and macOS iPhone Text Message Forwarding security.How iMessage sends and receives messages.Adding transit and eMoney cards to Apple Wallet.Rendering cards unusable with Apple Pay.Adding credit or debit cards to Apple Pay.How Apple Pay keeps users’ purchases protected.Intro to app security for iOS and iPadOS.Protecting access to user’s health data. ![]() How Apple protects users’ personal data.Activating data connections securely in iOS and iPadOS.Protecting user data in the face of attack.Protecting keys in alternate boot modes.Encryption and Data Protection overview.UEFI firmware security in an Intel-based Mac.Additional macOS system security capabilities.recoveryOS and diagnostics environments.Contents of a LocalPolicy file for a Mac with Apple silicon.LocalPolicy signing-key creation and management.Boot process for iOS and iPadOS devices.Secure intent and connections to the Secure Enclave.Face ID, Touch ID, passcodes, and passwords.
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