FriendWithA is built on top of one of the most secure systems in the world. When you submit your ID, FriendWithA takes extensive measures to ensure your ID is protected.
1. ID and selfie images are only ever stored encrypted with unique keys and those keys are stored separately, so that a) even if the files are leaked they can't be decrypted and b) if a key is leaked for one person's documents, the rest of them remain secure. The files are only decrypted on the fly when accessed by authorized administrator during review process.
2. After the images for a user have been reviewed by the administrator, they are additionally encrypted with a key stored in yet another location, secure even in the event of catastrophic system penetration. (Asymmetric encryption is used here so that the decryption key never needs to be involved in the encryption process and therefore can remain securely stored outside the system.)