Frequently Asked Questions

Sid has its own address scheme, the so called Sid Address which is formed by the given username and appended with an Asterisk (*) and a 5 digit unique number: your.username*12345

This allows you to use Sid anonymously without specifying personal data. Also each user can freely choose his or her user, even if it is already used by other users.

Note: If you delete Sid on all your devices (smartphone, desktop, tablet, etc.), the Sid address and all contacts/teams are irretrievably lost! So it is useful to install Sid on at least two devices to ensure a backup of your Sid address.

We assume that the users use Sid on smartphones and computers, which are already protected by a password or a PIN.

There is no user account, only your Sid address is registered. So it is not necessary to log in to a server with a password, as usual. Authentication to the server is secured by a private 256bit key. This corresponds to a password with more than 40 characters. This key is only stored on your device.

All your data and communication are only stored on your devices and not on external servers on the Internet.

Sid can be used anonymously without specifying personal data. To use Sid, you only need a Sid address. The Sid address is automatically created from your user name, which is expanded by an asterisk (*) and a 5-character unique number.

All messages and files are transmitted end-to-end-encrypted, the keys for encryption are only stored on your devices.

All transmitted data is only available on your devices or when data is exchanged in teams, on the devices of the team members. No data is stored centrally on a server.

Your Sid address with all contacts, teams and chats are encrypted inside a database that is stored on the device on which Sid is installed only and nowhere else. So you have full control over your privacy, but you also bear the responsibility for backing up your data.

But do not worry, with Sid this is quite easy: Connect at least one other device (desktop, mobile, tablet) with your Sid address. That's it. Sid automatically synchronizes all data on all your paired devices.

[How to pair devices...]

Sid stores all your data, messages, contacts, and profile information only on your devices. Your account and content only exists there. In the event of a loss the account can only be restored from another of your devices.

After you first start Sid on a new device, select "Add this device to my Sid network". Enter your Sid address in the next step and accept the confirmation request on your other Sid device.

[How to pair devices...]

For every file transfer, Sid automatically establishes a direct peer-to-peer connection between the devices involved. This way, files, such as pictures, photos, documents and videos of all types and sizes, are always transferred the most direct way from device to device without having to take a detour via another server. Within groups and multi-client connections, the devices of all group members serve as transmitters and are additionally available as backup media.

When data is exchanged between devices within a local network, like in an office situation, the data is transferred at highest speed possible, circumventing the bottleneck of the upstream speed and capabilities of the internet connection.

Additionally to this speed increase the most direct network connection also represents a security advantage for the transferred data as it is taking the most direct route. Using Sid means that in many cases your transferred data does not have to leave your local or office network.

Sid consistently uses end-to-end encryption for each message and file that is transmitted. The secret keys are generated directly on the device and only stored there or distributed through secure channels among them.

Whenever keys are exchanged between communication partners, asymmetric key exchange is used. Sid uses Curve25519 elliptic curve for all key exchanges, where the secret keys for each communication end-point is unique.

For all stream/transfer encryption Sid uses Salsa20 from renowned cryptographer Daniel J. Bernstein, who is also the creator of Curve25519. For the implementation of Curve25519 and Salsa20 algorithm the unmodified and audited C reference implementations are used.

End-to-end encryption is always enabled and can not be turned off.

More information about the encryption used can be found here: Security by Design

Sid supports SOCK5 and HTTP Connect proxy types. The proxy should be automatically detected on startup but can be configured or turned off in the options dialog.

Please make sure that the proxy allows outbound TCP connections to port 3030 for secure messaging and port 3033 for secure file transfer.

In case you have problems or encounter bugs with Sids proxy support please contact us at