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Product

What is Seald?

Seald is a one-click encryption tool that keeps unwanted eavesdroppers out of your conversations. Our goal is to protect the privacy of Internet users, regardless of their skills or the application on which they communicate. That's why we developed Seald, a tool for the general public and companies. It enables users to secure files and messages directly on the websites and applications they already use (e-mail, Facebook, Slack, Dropbox, etc.) with an intuitive design.

How does it work?

When installed on your computer, Seald automatically installs an extension in your browser (Google Chrome only for the moment) and apps (Slack Desktop for now).

Messages (Browser/App): In your browser or app, in any input on any website, write a message (an email, a post, a direct message, an article...), highlight the part of the message you want to encrypt, right click and click on Seald. Then, a "Select recipient" window appear where you can choose who will be able to open your message.

Documents (Desktop): Open Seald (on your desktop), drag and drop a document in the drop zone and select who will be able to open your document. It doesn't send it automatically! It just encrypts it.

Here is a video of how it works: demo.

Does Seald have an access to my message/document?

No! Our servers never see neither your messages nor the keys to decrypt them! Our servers only get encrypted message keys, that can only be decrypted with the private key which never leaves your device.

Can I use Seald for free?

Seald provides a free version that can be used to encrypt and decrypt files and messages. A pro version will be released with additional features intended for system administrators and team managers.

Getting started

Which platform does Seald Support?

Right now, Seald supports macOS and Windows computers.
In the future, we plan on releasing versions for Linux, iOS, and Android devices (and possibly other platforms, depending on the demand).

Where can I use it?

Seald works on Google Chrome and Slack desktop app for the moment. Other browsers and desktop applications will be supported in the future, starting with Firefox.

On Google Chrome, Seald should work on any website (Facebook, Gmail, Messenger, Slack, Outlook...). As long as you have an input, you can encrypt your message in it.
If you run into trouble on any website, please contact us and we'll try and sort it out.

For companies, don't hesitate to contact us! We can work together to see how Seald could be integrated with your chat & communications software.

Does the recipient need to have Seald installed?

At the moment yes. Seald does not provide a way to send a message to someone who hasn't got Seald installed... yet.

I can't Seald a message on Chrome.

I don't have a 'Seald' option in the context menu:
Is the Chrome extension installed correctly? You can check in Chrome's "extensions" tab. If it's not, you can install it from here.

After clicking 'Seald' in the context menu, nothing happens:
Are you sure the Seald app is open on your computer? The extension doesn't actually perform the encryption by itself, and cannot do anything if the app is not open. If the app is indeed launched, reloading the page or restarting your browser might sometimes help.

The Seald icon is not in the notification area (Windows)

Click on the arrow near the clock and click on personalize. Then, choose the option "Show icon and notifications" for Seald.

Security

Which algorithms are used?

The communications with the server are protected with TLS.

The algorithms used are:
- RSA-4096/OAEP-MGF1(SHA1) (and CRC32 for controlling integrity) for asymmetric encryption
- RSA-4096/PSS-MGF1(SHA256) on the SHA256 of the symmetric key + message for signature
- AES-256/CBC with a 16 bits IV + HMAC-SHA256 for symmetric encryption.

What is the protocol?

When you install the app, an RSA-4096 keypair is generated on your computer, the public key is sent to the Seald server.
The email you receive during the installation is a challenge that your Seald app sends back signed with your private key. Once the signature is checked, your public key can be retrieved when searching for your email.

When you encrypt a message or a document, a unique message ID is given by the server.
A random key is generated, and is encrypted for the public keys of the recipients you chose and your public key as well.
Those encrypted keys are sent to the server and can be retrieved by each recipient.
Then the message is signed, and the signature is sent to the server as well.
The Seald message contains the message ID and the encrypted message (or file) and can be sent through any communication channel.

For messages, it's encoded as such:
==GET=SEALD=${protocolVersion}=${messageID}=${encryptedMessage}/=
protocolVersion: version of the protocol.
messageID: it's a UUID encoded with a modified base64 encoding.
encryptedMessage: the encrypted message encoded with a modified base64 encoding.

We use a modified base64 encoding because of some websites that use a styling syntax that conflicts with base64URL or traditional base64, which would result in broken Seald messages.

For files, it's encoded as such:
SEALD.IO_${headerSize}${header}${encryptedFiles}
The headerSize is encoded on a 4 byte integer
The header is encoded in BSON and contains the following keys:
'v' for protocol version
'mid' for messageId
The files are not encrypted directly, they are archived in a tarball (USTAR format with pax headers) before encryption.

When you try to decrypt a message (or a file), your Seald app retrieves the symmetric key encrypted for you (if it's available), decrypts it, and uses it to decrypt the message.
The signature is also checked.
If any one of those operations fails, Seald will only throw an error.

Still have questions?
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