Unit 2A, 17/F, Glenealy Tower, No.1 Glenealy, Central, Hong Kong S.A.R.
Privacy and security
What is protected, what is not, and why we say so
Every messaging product claims encryption. This page says which part of the journey ours applies to.
The claim
A narrow promise, kept
We would rather tell you the exact shape of the protection than sell you a word.
SimTether protects your messages from the moment they leave the phone at home until they open on the phone in your hand, and it is built so that the server in between keeps nothing readable and nothing at all for long. It does not protect the SMS while it crosses the mobile network, because nothing can. Read the next section before you read the good news.
The limit
An SMS is a postcard before it ever reaches us
Text messages were designed in the eighties and they travel in the clear. Your operator can read them, the sender's operator can read them, and so can anyone with lawful access to either. That is true of every SMS you have ever received, whether or not SimTether exists.
The phone at home has no key material and no way to get one safely, so the message is sealed by the relay on arrival rather than before it leaves. This is a real difference from a chat app where only the two ends ever hold a key, and we are not going to describe it with a word that hides it. What follows is what that sealing genuinely buys you.
Stated plainly
·
The mobile network reads your SMS. We cannot change that.
·
The relay seals messages on arrival, so it is the point where sealing begins.
·
Nothing here has been independently audited.
·
This is a tool for reaching your own messages, not a tool for hiding.
What is protected
From the relay to your hand
Four things that are true of every message the system carries.
Sealed before storage
A message is encrypted before it is written to disk, so nothing readable is ever at rest on the server.
Opened only on your device
The key that opens it is generated on your phone during pairing and never leaves it. A copy of the database is of no use without it.
Deleted on delivery
Once your phone confirms it has the message, the relay drops its copy. There is no archive to request, subpoena or steal.
Content-free pushes
The wake-up notification says only that something arrived. Apple and Google never handle the text of your messages.
What we refuse to hold
The safest data is the data that was never collected
Most of the privacy here comes from absence rather than from cryptography.
No identity
No email address, no name, no password, no profile. There is no account to breach because there are no accounts.
No history
Your conversations live on your phone. The server holds a message only for the gap between the two devices being awake.
No analytics
No tracking SDK, no advertising identifier, no third party in the apps at all. Nothing reports what you read or when.
No address book
The app never asks for your contacts and could not upload them if it wanted to. Numbers stay numbers.
What is stored
The complete list of what the server holds
Four rows. If something is not on this list, it is not stored.
Paired devices
A public key per device, so a message can be sealed for it. Removing a device removes the key.
Handsets
Which forwarders exist and when each last checked in, so the app can tell you one has gone quiet.
Messages in flight
Sealed, and only until the destination device confirms it has them. Then the row is deleted.
Pairing tokens
Single-use, valid for two minutes, and marked spent the instant they are used.
The checklist
Twelve statements you can hold us to
Each one is either true of the system today, or it is not written here.
No account, no email, no password
No user directory to look you up in
Messages sealed before they are stored
Opening keys held only on your device
Delivered messages deleted from the server
Push notifications with no content
Pairing codes that work once, for two minutes
A paired device can be cut off at any time
No analytics and no advertising SDKs
No access to your contacts
Face ID lock on the app itself
Stated limits, on this page, in writing
SimTether has not been independently audited, and an SMS crosses the mobile network in the clear long before it reaches the phone at home. We protect everything after that point, and we say so plainly rather than calling it end-to-end encrypted.
Get in touch
Tell us what you need to reach
One SIM or four, one country or three: describe the situation and we will tell you honestly whether this solves it.
Head office
Unit 2A, 17/F, Glenealy Tower, No.1 Glenealy, Central, Hong Kong S.A.R.
Email us
SimTether
SimTether puts the texts from the SIM you left at home on the phone you carry, and lets you answer from the same number. Free, with no account.
Contact
Unit 2A, 17/F, Glenealy Tower, No.1 Glenealy
Central, Hong Kong S.A.R.
Monday to Friday, 09:00 to 18:00 HKT
Occasional updates
One short email when there is something real to say, such as the app reaching the App Store. Nothing else.
SimTether is software for reaching your own messages. It is not an operator, it does not issue numbers, and it does not port anything.
© 2026 HK Managed Services Provider Limited. All rights reserved.