We never share your data with anyone. No.
SafeUM only stores the data it needs to function properly — for as long as you want SafeUM to function.
We store messages, photos, videos and documents from your ordinary chats on our servers, so that you can access your data from any of your devices anytime and use our instant server search to quickly access your messages from waaay back. All data is stored heavily encrypted and the encryption keys in each case are stored in several other DCs in different jurisdictions. This way local engineers or physical intruders cannot get access to user data.
Secret chats use end-to-end encryption. This means that all data is encrypted with a key that only you and the recipient know. There is no way for us or anybody else without direct access to your device to learn what content is being sent in those messages. We do not store your secret chats on our servers. We also do not keep any logs for messages in secret chats, so after a short period of time we no longer know who or when you messaged via secret chats. For the same reasons secret chats are not available in the cloud — you can only access those messages from the device they were sent to or from.
When you send photos, videos or files via secret chats, before being uploaded each item is encrypted with a separate key, not known to the server. This key and the file’s location are then encrypted again, this time with the secret chat’s key — and sent to your recipient. He can then download and decipher the file. This means that the file is technically on one of SafeUMs servers, but it looks like a piece of random undecipherable garbage to everyone except for you and the recipient. We don’t know what this random data stands for and we have no idea which particular chat it belongs to. We periodically purge this random data from our servers to save disk space.
SafeUM uses phone numbers as unique identifiers, so that it is easy for you to switch from other messaging apps (SMS, WhatsApp, etc.) and retain your social graph. We ask your permission before syncing your contacts.
We store your contacts in order to notify you as soon as one of your contacts signs up for SafeUM and to properly display names in notifications.