Sealed call evidence
Your phone can record. Kerux proves it wasn't edited.
Call from Kerux and switch on evidence. Our server records the call itself and seals it the moment you hang up, before anyone can touch the file, then encrypts it so only you can open it. Anyone you share it with can check the seal, with free tools, without trusting you or us.
No email, no sign-up form. Works in any browser, and on Android as an app.
The problem
A recording proves nothing about itself.
Recording a call is free now: your phone does it. But when a recording is challenged, the person who made it has to show it is the original and that nothing was changed. A file on a phone carries its own dates and details, and anyone can edit those.
Courts look for proof from outside the file. In Quebec, the Court of Appeal has held that a recording's own metadata may not be enough, on its own, to show it is authentic (Benisty c. Kloda, 2018).
Kerux is that outside proof: an independent server that recorded the call and sealed it before you ever held the file.
What gets asked
Five questions every recording faces, and how Kerux answers them.
Is this the original, unchanged?
Kerux computes a SHA-256 fingerprint of the exact audio seconds after you hang up. Change a single bit and the fingerprint no longer matches.
When was it made?
At sealing, the Soteria Chancery stamps the fingerprint with a standard RFC 3161 timestamp, and it is anchored in the Bitcoin blockchain with OpenTimestamps: public records no one can backdate, us included.
Who had it before it was sealed?
No one. Our server records the call itself and seals it before the file exists anywhere else. You never hold an unsealed copy.
Was it recorded by someone on the call?
You confirm you are on the call and allowed to record before evidence turns on. That statement, and the moment you confirmed it, are part of the proof.
Can it be checked without trusting you?
Yes. The fingerprint, the timestamp and the steps use open standards. Anyone can check them with free tools, even if Kerux disappears.
What you file
One page that anyone can check.
Every sealed call comes with a Proof of Integrity: what our server recorded and sealed, signed by Kerux, with a code anyone can scan. This sample is real: a call to the free test line, sealed in November 2026.
- Signed with the Kerux seal key: anyone can check the signature.
- Witnessed at sealing by the Soteria Chancery, part of the same group as Kerux.
- Anchored in Bitcoin with OpenTimestamps.
- In English and French, and still available after the recording is gone.
Sealed at the call, not at upload
Recording is free. Proof is not. Proof made later is weaker.
Some services certify a file you upload. Their proof starts when you upload it, not when the call happened, and it cannot show what happened to the file before.
| Phone recorder | Upload-and-certify services | Kerux | |
|---|---|---|---|
| Records the call | Yes | No, you bring the file | Yes, on an independent server |
| Proof dated | Never: only the file’s own date | When you upload | When the call ends |
| Could the file be edited before the proof? | Yes | Yes, before upload | No, sealed before you get it |
| Who can listen | Whoever has the phone | Depends on the service | Only you |
| Safe if you lose your phone | No | Depends on the service | Yes, an encrypted copy for 90 days |
| Checked without the vendor | Nothing to check | Depends on the service | Yes, open standards and Bitcoin |
How it works
Four steps, one call.
Dial from Kerux
Type the number. The person you call sees the Kerux number.
Switch on evidence
Confirm you are on the call and allowed to record it. Leave it off and nothing is kept.
Hang up
The recording is sealed and encrypted to your key within seconds.
Keep and share
Download the recording with its proof. Send the proof link to whoever needs it.
For the skeptics
What the seal is made of.
Nothing here is secret or proprietary. That is the point: the proof has to stand without us.
- Fingerprint
- SHA-256 of the exact audio, computed in our server’s memory before encryption. The plain audio is never written to disk.
- Timestamp
- An OpenTimestamps proof that anchors the fingerprint in a Bitcoin block: it existed at or before that block.
- Second witness
- At sealing, the Soteria Chancery stamps the fingerprint (RFC 3161) and keeps a public receipt. It belongs to the same group as Kerux; its stamp checks with openssl and its public root, without trusting either.
- Ledger
- Every seal is appended to a hash chain: each entry depends on the one before, so no entry can be removed or altered quietly.
- Encryption
- The audio is encrypted to your account’s own key. Our server keeps only the encrypted copy and cannot open it.
- Public record
- Anyone can ask Kerux whether it sealed a fingerprint, and when, without sending the audio, your number or your account.
- Your bundle
- The recording, PROOF.md with every value, the timestamp proof, the consent record, and the steps to check it yourself with
sha256sumandots verify.
After you hang up
The seal, step by step.
Hang-up
The audio exists only in our server’s memory.
Seconds later
Fingerprinted: SHA-256 of the exact audio.
Next
Encrypted to your key. The plain copy is erased.
Then
Stamped by the Soteria Chancery (RFC 3161) and sent to Bitcoin.
Within hours
A Bitcoin block confirms the timestamp. No one can backdate it.
Who uses it
For the call you'll need to prove later.
Tenants
The repair your landlord promised, the notice they gave by phone.
Employees
What your manager said about your hours or your pay.
Co-parents
The schedule change agreed on the phone, with any number you call.
Consumers
What the collector or the company told you, word for word.
Small businesses
The price, the date, the promise a client or supplier made.
Prices
Pay for the proof, not a subscription.
Prepaid credit, in US dollars. Calls cost from 2 cents a minute; unanswered calls are free.
Test line
Free
Call 0000 and see a sealed recording from start to finish before you add any credit.
Sealed call
$5
Per recorded call, charged only when a recording was sealed. The signed Proof of Integrity is included.
Case Pass
$49
Unlimited sealed calls for 90 days, and every recording kept 2 years, to your hearing. Paid once, never renews by itself.
Questions
What people ask before their first sealed call.
Is it legal to record a phone call?
In Canada, you may record a call you are part of (one-party consent). In the United States most states allow it too, but some require everyone on the call to agree. Kerux only records calls you are on, after you confirm it. We can’t tell you whether your situation allows it: when in doubt, ask a legal clinic.
Will a court accept it?
A judge decides. Kerux gives the judge what is usually asked of a recording: proof that it is the original, when it was made and that nothing changed, from someone other than you.
Can Kerux hear my calls?
No. During the call the audio passes through our server’s memory. When it ends, the recording is encrypted to your key and the plain copy is erased. Calls without evidence are not recorded at all.
What does the other person see?
The Kerux number, not yours.
What if Kerux disappears?
Your proof stays checkable. The fingerprint, the Bitcoin timestamp and the RFC 3161 token use open standards and free tools. Keep your ZIP.
What if I lose my phone?
Restore your account on another device with your 12 words: your recordings are still there for 90 days, or 2 years with a Case Pass. Lose the words and we can’t recover them.
Do you need my name or my email?
No. Your account is a 12-word phrase made on your device. Nothing else.
Which numbers can I call?
Numbers in Canada and the United States, for now.
Plainly
What Kerux proves, and what it doesn't.
It proves
- The file is exactly what our server recorded.
- It existed, unchanged, at the sealed time.
- The call was placed through Kerux to that number.
It doesn't
- Prove who was speaking.
- Decide what a court accepts: a judge does.
- Replace advice from a lawyer or a legal clinic.
Your part
- Record only calls you are on.
- Some places require everyone on the call to agree. Check the rules where you and the other person are.
- Keep your 12-word phrase: lose it and your recordings are gone. We can’t recover them.
Received a proof link or a fingerprint?
Paste the 64-character fingerprint to see what Kerux sealed, and when. Nothing else is needed.