Fully offline OpenPGP encryption for Apple platforms — zero network, minimal permissions. CypherAir X is an open-source OpenPGP tool for people who want to communicate securely without cryptographic knowledge: encrypt, decrypt, sign, and verify, with keys and contacts managed entirely on device. It is a SwiftUI app over a Rust OpenPGP engine (Sequoia PGP) bridged through UniFFI.

• Platforms — iOS 26.5+ / iPadOS 26.5+ / macOS 26.5+ / visionOS 26.5+; 8 GB RAM minimum.
• Zero network access — no HTTP(S), no networked SDKs, no telemetry, no update checks; the app works in airplane mode. The evidence chain lives in docs/SECURITY.md.
• One usage description — NSFaceIDUsageDescription, for local biometric authentication, injected from the INFOPLIST_KEY_NSFaceIDUsageDescription build setting in CypherAir.xcodeproj (CypherAir-Info.plist declares none). No camera, photo library, contacts, or network permission; any other entitlement in the project is a resource, sandbox, or hardening entitlement, not a privacy permission.
• Nine key families — five portable (software custody, exportable) and four device-bound (Secure Enclave custody, never exportable), chosen at key generation and immutable per key. Canon: Sources/Models/Keys/PGPKeyFamily.swift; promises: docs/PRODUCT.md; custody: docs/CUSTODY.md.

• macOS on Apple Silicon with Xcode; pinned development and release toolchain versions are in CLAUDE.md "Tech Stack".
• Rust stable with the five Apple targets: rustup target add aarch64-apple-ios aarch64-apple-ios-sim aarch64-apple-darwin aarch64-apple-visionos aarch64-apple-visionos-sim
• Steps 2 and 3 need network access — they download and verify pinned prebuilt artifacts. Zero-network is a property of the shipped app, not of its build toolchain.

The repository ships a project-level .mcp.json configuring an xcode MCP server (/usr/bin/xcrun mcpbridge), which gives agent sessions Apple Developer Documentation search and build/diagnostic tools. Other MCP-capable agents configure the equivalent server command.

# 1. Validate Rust behavior
cargo +stable test --manifest-path pgp-mobile/Cargo.toml

# 2. Refresh the XCFramework and generated bindings that Xcode links. The script
# defaults to the current arm64e stage1 pin (docs/ARM64E_STATUS.md), never `latest`.
ARM64E_STAGE1_FORCE_DOWNLOAD=1 ./build-xcframework.sh --release

# 3. Restore the pinned SQLCipher dependency (git-ignored artifact, attested on fetch)
scripts/restore_sqlcipher_xcframework.sh

# 4. Validate Swift unit + FFI behavior locally
xcodebuild test -scheme CypherAir -testPlan CypherAir-UnitTests \
    -destination 'platform=macOS,arch=arm64e'

# 5. Probe the native visionOS app build
xcodebuild build -scheme CypherAir -destination 'generic/platform=visionOS'

Secure Enclave, biometric, and MIE coverage runs on real hardware — an Apple Silicon Mac or a physical device — via the CypherAir-DeviceTests plan; macOS UI smoke coverage via CypherAir-MacUITests. There is no dedicated visionOS test plan; the build probe above plus the Rust and macOS lanes cover it. Lanes and plans: docs/TESTING.md. Release flow, published artifacts, and stale-artifact troubleshooting: docs/BUILD.md.

• PRODUCT — product promises, deliberate non-features, consent gates, compatibility
• SECURITY — threat model, fail-closed rules, authentication, coding red lines
• CUSTODY — per-family custody, access control, split custody, interop position
• STORAGE — storage posture, protected domains, documented exceptions, envelope version map
• ARCHITECTURE — layer boundaries and the Rust/FFI contract rules
• BUILD — stable release flow, published artifacts, arm64e toolchain contract, carry chains, and the Rust↔Xcode sync contract
• TESTING — test layers, plans, and CI lanes
• WORKFLOW — development loop, "done" requirements, security gate, documentation contract
• ARM64E_STATUS — the machine-parsed arm64e stage1 pin

Unless otherwise noted, first-party CypherAir source code in this repository is made available under either of the following licenses, at your option:

• GNU General Public License, version 3 or any later version
• Mozilla Public License, version 2.0

SPDX expression for first-party code: GPL-3.0-or-later OR MPL-2.0.

Full license texts are provided in LICENSE-GPL and LICENSE-MPL.

The OpenPGP engine uses Sequoia PGP (LGPL-2.0-or-later).

Third-party components remain under their own licenses. See the bundled notices and repository documentation for third-party license details and distribution compliance materials.