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SafeSlinger - Frequently Asked Questions

How do I exchange public keys or "Sling Keys" with other users?
At minimum, you need to install SafeSlinger on your phone as well as the other user's phone, and an Internet connection must be active on both phones. When exchanging keys, you only need to compare one number and one 3-word phrase with other users. When doing this comparison, you must be able to either see the other user's phone screen or hear the number and phrases spoken so you can verify the physical presence of the other user. See our exchange instructions page for more information. SafeSlinger logo

How do I exchange public keys if I'm not in the same room with another user?
Since you may perform an exchange if you can hear the other user at the same time, you may call another user to make the exchange. However, since some cellular carriers do not permit an Internet connection to be active while making a voice call, you may consider using another Internet service like video chat on your phone, or a separate landline in that case.

How do I send messages with this app?
Our messaging instructions page provides a short walkthrough to use the application.

How safe is SafeSlinger?
SafeSlinger provides secure communications. Unless a third-party can compromise the operating system on the phone, it cannot access the content of SafeSlinger messages or any other data.

Is it dangerous to provide such high security?
SafeSlinger provides the same high degree of messaging security for end users as PGP which has been available since the early 90's. However, PGP can be slow for users to setup and spend time comparing public keys of every user to ensure that messages they receive using those keys belong to the people you expect. SafeSlinger makes the existing high-security systems easy to use and approachable.

Which Agencies or other third-parties have access to my information in SafeSlinger?
There are no backdoors in our system. SafeSlinger does not provide backdoors to access any of your data, messages or contacts.

Is this open source? When will the source code be available?
The Android client, iOS client, and App Engine server source code is available on GitHub.

How can you ensure both the authenticity of users and also provide secrecy of our information at the same time?
We interleave several cryptographic techniques in our protocol to provide these properties. The full details of our system are described in our research paper.

What if the server is compromised?
Our server is implemented on Google App Engine and is used simply to exchange contact and message data that has already been encrypted. Even if the server is compromised, it cannot reveal your message content or any other data you send.

Why does SafeSlinger need access to the Internet?
All SafeSlinger messages are encrypted between users and the Internet is used as the most commonly available communication channel for users to send and receive messages.

Why does SafeSlinger need access to my contacts?
SafeSlinger allows each user to choose what contact information (phone, email, address) to share with other users along with their SafeSlinger public keys. All contact data is encrypted before leaving your phone and can only be decrypted on the other user's phone. If a user chooses to send you their email, phone, or address information, SafeSlinger will import that information into your Contacts for you. Each user determines how much, if any, contact data is shared with other users.

Why does SafeSlinger need to send me Push Notifications?
SafeSlinger uses push notifications to receive encrypted messages that other users send you.

Why does SafeSlinger need access to iCloud or Android Backup?
This is an optional feature which can backup your encrypted application key to the cloud in case you want to move your account to another phone. Only your passphrase can decrypt your application key. Currently backup is supported only between devices using the same operating system (Android to Android and iOS to iOS), and not all manufacturers support backup.

I forgot my SafeSlinger password, how can I recover it?
We do not allow recovery or resetting of forgotten passphrases. You may generate a new application key instead. However, If you use our application key backup feature this can be difficult and we are testing ways to make the process more user-friendly. One workaround is to: 1. Disable your device's backup settings, 2. Uninstall SafeSlinger, 3. Reinstall SafeSlinger and run the application until setup is complete, 4. Reenable your device's backup settings.

Even though my messages are unreadable by anyone but the person I send it to, how long does my message spend on the server?
Messages are automatically removed after 24 hours.

What happens to my messages and attachments after I decrypt them?
Messages are kept in the app database on your phone, and require a passphrase to access. Attachments (pictures, documents) are saved to the operating file system storage or storage card so you can manage them with the default application for each type of attachment (Gallery, Document Viewer).

How do I send multiple attachments?
SafeSlinger currently only supports adding one attachment to a message at a time.

How to I send a message to multiple users?
SafeSlinger currently only supports sending one message to any user at a time.

Does SafeSlinger support Android 4.4?
Android OS 2.3 to 4.4 are currently supported.

Does SafeSlinger support iOS 7?
iOS 6 and 7 are currently supported.

Does SafeSlinger support Windows Phone?
Not at this time. You can check this page for future support updates.

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