How should I manage the watermark key?
The key seeds the spreading sequence used to embed and detect the ID. It is obfuscation-grade, not a cryptographic passkey: a wrong key produces noise rather than an authentication error, and it does not encrypt the audio. Keep one strong secret per campaign, store it with the private manifest, and never ship it with the promos.
How Aureal handles it
The key is hashed to a 32-bit seed that drives the pseudorandom sequence; the same key must be used at embed and detect time. There is no cryptographic key derivation, rotation or revocation in the file format, so changing the key means re-embedding and keeping the old key for old copies. The built-in default is a fixed public constant; a file marked with it can be detected, and matched, by anyone. The batch manifest stores the key because an audit needs it, which makes the manifest as sensitive as the promos. Re-marking a file with the same key and a conflicting ID can destroy the original ID.
Common failure mode
“The key encrypts the audio, so a leaked promo is unreadable without it.”
Why it fails: Watermarking does not encrypt or restrict playback; the audio is fully listenable. The key only controls the spreading sequence and the detection result. A wrong key yields noise, not a decryption failure, and the default key is public.
Verified example
Use a unique, high-entropy key per campaign and separate it from the audio:
1. Generate the key in a secret manager, not in a shell history.
2. Pass it to the batch tool from the environment.
3. Store it with the private manifest, not in the promo folder.
4. Back it up; losing it means the old copies cannot be detected.
Never commit the key or include it in a public report.Example only. Validate against your own audio, codec and processing chain.
Scope and limits
- Obfuscation-grade seed, not encryption or authentication.
- The built-in default key is public; use it only for tests.
- No rotation or revocation; changing the key requires re-embedding.
- The manifest contains the key and must stay private.
Frequently asked questions
Can I change the key later?
New copies can use a new key, but old copies still need the old key to detect. There is no in-file rotation or revocation, so keep the old key for as long as the old distribution matters, and re-embed if you need one key across everything.
What happens if I use the default key?
Anyone can detect files marked with it, and anyone can embed a matching ID. It is a test default, not a distribution secret. Use the --key option for real work.
Related topics
Test the actual delivery chain. A fixture result is a starting point, not a guarantee for your material.
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