android_cast/ndk/obfuscate

Entitlements obfuscation (C)

Shared by libandroidcast_entitlements.so and the archived spike under reference-design/obfuscate_entitlements/.

• encode / decode — 40-bit payload + 24-bit verification tag, keyed by per-account uint64_t key (not wall clock).
• write_to / read_from — file layout: 32-bit dummy header, N×uint64_t payloads, 32-bit dummy tail.

Reference demo: tmp/obfuscate_test/ (standalone; not wired into the main app).