Adaptive Physical Communication System (APCS)

Permissions and Privacy

Every permission the app asks for, why it needs it, when it asks, and what happens if you say no. It also describes what data the app handles and where that data goes (in short: nowhere except the other phone, through the air in front of you).

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Privacy summary
Android permissions
iOS usage descriptions
Web
When permissions are requested
If a permission is denied
Data handling
Physical privacy

1. Privacy summary

No network in the data path. The app declares no INTERNET permission in its main manifest (Flutter adds one only to debug builds for hot reload). Messages move only as light, sound or vibration between phones in the same room.
No accounts, no analytics, no ads, no cloud.
Nothing is stored except what you choose to keep: received photos and videos are saved to your Gallery, and the chat history lives in memory until the app closes.
Anyone nearby can receive a Light or Sound broadcast. There is no encryption (Security). Treat it like speaking out loud in a room.

2. Android permissions

From android/app/src/main/AndroidManifest.xml:

Permission	Type	Why	Used by
`CAMERA`	Runtime (dangerous)	Read the sender’s QR codes	Light receive
`RECORD_AUDIO`	Runtime (dangerous)	Hear the sender’s tones	Sound receive
`MODIFY_AUDIO_SETTINGS`	Normal	Route audio for recording and playback	Sound
`VIBRATE`	Normal	Drive the vibration motor	Vibration send
`WAKE_LOCK`	Normal	Keep the screen on while streaming QR codes	Light send
`WRITE_EXTERNAL_STORAGE` (max SDK 29)	Runtime on Android ≤ 10 only	Save received media to the Gallery on old Android versions	Gallery saving

Features android.hardware.camera and android.hardware.microphone are declared not required, so the app installs on devices without them (those channels are then unavailable).

Not needed:

The accelerometer needs no permission on Android.
Screen brightness is changed only for this app’s window (WindowManager.LayoutParams.screenBrightness through the apcs/optical_display channel), which needs no permission. It is restored when streaming stops.
Gallery on Android 10+ uses MediaStore through gal, with no storage permission.

3. iOS usage descriptions

From ios/Runner/Info.plist. iOS shows these texts in the permission prompts:

Key	Text shown to the user
`NSCameraUsageDescription`	“Camera is used to receive optical communication signals from nearby devices.”
`NSMicrophoneUsageDescription`	“Microphone is used to receive acoustic communication signals from nearby devices.”
`NSPhotoLibraryAddUsageDescription`	“Received photos and videos are saved to your photo library.”
`NSPhotoLibraryUsageDescription`	“Received photos and videos are saved to the Adaptive Comm album.”
`NSMotionUsageDescription`	“Motion sensors detect vibration patterns from a physically coupled nearby device.”

4. Web

Browsers ask for the camera and microphone the first time they’re used, and only on HTTPS or localhost pages. There is no vibration motor access for this purpose and no Gallery saving on the web.

5. When permissions are requested

The app asks only when a feature needs it, never at start-up:

Permission	Asked when	Code
Camera	You start receiving by Light	`HardwareOpticalChannel` → `Permission.camera.request()`
Microphone	You start receiving by Sound	`hardware_channels.dart` → `Permission.microphone.request()`, then `AudioRecorder.hasPermission()`
Photos / Gallery	The first photo or video is saved (automatically on receipt, or with Save to Gallery)	`GallerySaver` → `Gal.requestAccess(toAlbum: true)`
Motion (iOS)	Normally never: iOS gives raw accelerometer data without a prompt. The usage string is declared in case the system asks	`sensors_plus` accelerometer stream

Sending by Light needs no permission (it only draws on the screen). Sending by Sound needs none either (it only plays audio).

6. If a permission is denied

Denied	Effect	How to recover
Camera	Light receive shows no camera preview (“Camera permission denied” in the developer logs)	Settings → Apps → Adaptive Comm → Permissions → Camera, then reopen Receive
Microphone	Sound receive shows “Microphone permission required” and an Enable microphone button	Tap the button, or Settings → Apps → Adaptive Comm → Permissions → Microphone
Photos	The message still appears in the chat; the status reads “Photo received — Gallery permission denied”. Nothing is lost	Allow photos in Settings, then tap Save to Gallery

Other channels keep working when one permission is denied.

7. Data handling

Data	Where it lives	How long
Messages you send	Memory (chat list); encoded into QR frames / audio / vibration	Until the app closes
Messages you receive	Memory (chat list)	Until the app closes, or you clear the chat
Received photos/videos	Also written to the Gallery album Adaptive Comm	Until you delete them
Temporary files	App temp directory: `rx_img_.jpg`, video playback files, `APC_` Gallery staging files (deleted right after saving)	Cleared by the OS or on reinstall
Camera frames	Luminance copied into memory for decoding, then discarded; never saved	Milliseconds
Microphone audio	Streamed through the decoder, never saved	Milliseconds
Accelerometer samples	Processed live, never saved	Milliseconds
Logs	In memory (developer screens)	Until the app closes

No data is sent to any server, and there is no crash reporting or telemetry.

8. Physical privacy

Because the channels are physical, so is the privacy:

Light can be read by any camera that sees the sender’s screen, including one filming from across a room at high zoom. Shield the screen if the content is sensitive.
Sound is audible to everyone nearby and can be recorded and decoded later.
Vibration needs physical contact, so it’s the most private channel, but also by far the slowest.

For confidential content, wait for the encryption item on the Roadmap, or encrypt the file before sending it.

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