On-Device Cryptographic Signing

Professional verification.
One purchase. No subscriptions.

Deterministic proof that audio was captured by this app and remains unmodified. No cloud. No accounts. No AI detection.

The Provenance Problem

Trust in audio is collapsing due to AI synthesis and invisible editing. ProofAudio provides an explainable, deterministic way to prove provenance without relying on AI detection or third parties.

Cryptographic Signing

SHA-256 hash and P-256 ECDSA signature at capture time.

Offline Verification

Public key included in every proof bundle for independent validation.

Background Recording

Recording continues when your screen locks. No interruptions.

Status

Verified
LEVEL A
Integrity Unmodified
Location Start + End Captured
Continuity Uninterrupted
Privacy by Design

Your Data, Your Control

Explicit preservation, not automatic backup. Your recordings stay on your device unless you choose otherwise.

On-Device Only

All recordings stay on your device. No cloud uploads, ever.

No Backup Sync

Excluded from iCloud and iTunes backups. Your audio won't appear in unexpected places.

No Accounts

No sign-up, no tracking, no analytics. We don't know who you are.

Explicit Export

Export as sealed proof to preserve. You decide what leaves your device.

Trust Levels

More context means higher trust. All levels prove capture integrity; higher levels add contextual verification.

A

Verified Continuous

Hash + signature + location + motion + uninterrupted session. The highest level of verification.

B

Verified + Context

Hash + signature + location + motion. Contextual data adds confidence.

C

Verified Capture

Hash + signature + timestamp. Proof of capture and integrity.

Sealed Proof Sharing

Create password-protected .proofaudio bundles. Share through any channel—the encryption keeps it safe.

AES-256-GCM PBKDF2 (600k iterations) Unique salt per bundle

Destroy

Crypto-shred recordings. The encryption key is destroyed—without it, the audio cannot be recovered.

Location Snapshot

Rounded coordinates (~500m) at start and end. Never continuously tracked.

Motion Summary

Aggregated statistics only. Stationary, minor movement, or in motion.

App Lock

Optional Face ID, Touch ID, or passcode protection for the app.

Frequently Asked Questions

Everything you need to know about ProofAudio verification.

What does "verified" actually mean?

When a recording shows as "verified," it means:

  • The audio file has not been modified since capture
  • The cryptographic signature is valid
  • The recording was made using the ProofAudio app

It does not verify who is speaking, whether statements are true, or that consent was given to record.

Can ProofAudio detect AI-generated audio?

No. ProofAudio does not attempt to detect AI-generated audio, deepfakes, or synthetic speech. If someone plays AI-generated audio into the microphone, ProofAudio will sign it like any other sound.

What ProofAudio does prove is that the audio was captured through the app's microphone at a specific time and has not been modified since. This is fundamentally different from—and more reliable than—AI detection.

How does verification work?

When you record:

  1. The app captures audio and computes a SHA-256 hash
  2. A cryptographic signature is created using your device's Secure Enclave
  3. Optional context (location, motion, continuity) is collected
  4. Everything is bundled into a signed manifest

When verifying, the hash is recomputed and checked against the signature. If even one bit of audio has changed, verification fails.

Is my file uploaded when I verify?

No. The web verifier runs entirely in your browser using WebAssembly. Your file never leaves your device. The verification page has no network requests after initial load—you can even verify offline.

Why is a password required for .proofaudio files?

When you export a recording as a .proofaudio file, it's encrypted with a password you choose. This allows you to share the file through any channel (email, messaging, cloud storage) while keeping the contents private.

The encryption uses AES-256-GCM with PBKDF2 key derivation (600,000 iterations). Only someone with the password can decrypt and play the audio.

What are trust levels?

Trust levels indicate how much contextual data was captured alongside the audio:

  • A Verified Continuous — Hash + signature + location + motion + uninterrupted capture
  • B Verified + Context — Hash + signature + location + motion
  • C Verified Capture — Hash + signature only

All levels prove the audio is unmodified. Higher levels add more context about the recording circumstances.

Can timestamps be trusted?

Timestamps are device-reported. ProofAudio records the time according to your device's clock at the moment of capture. If your device clock is wrong, the timestamp will be wrong.

The app also records clock integrity signals (wall clock vs monotonic time) which can help detect if the device clock was changed during recording, but this is informational only.

Is ProofAudio admissible in court?

Admissibility depends on jurisdiction and context. ProofAudio provides cryptographic evidence of integrity that can support authentication, but legal admissibility is determined by courts, not technology.

Consult a legal professional for advice specific to your situation and jurisdiction.

Technical Specifications

For developers, security researchers, and the technically curious.

Cryptography

Signing Algorithm P-256 ECDSA
Hash Algorithm SHA-256
Key Storage Secure Enclave
Encryption AES-256-GCM
Key Derivation PBKDF2 (600k iterations)

Audio Format

Container M4A
Codec AAC
Sample Rate 44.1 kHz
Channels Mono

Location Privacy

Precision ~500m (3 decimal places)
Snapshots Start + End only
Continuous Tracking Never

Verification

Web Verifier 100% Client-Side
Technology Rust / WebAssembly
Network Requests None (after load)
File Upload Never

Important Limitations

ProofAudio proves capture integrity. It does not and cannot verify:

One price. No subscriptions.

Unlock all features with a single purchase. Record with confidence forever.

$49.99 One-time purchase — yours forever

Free version includes 3 recordings with basic verification.