Username Privacy
- Unlike other messaging apps, Signal cannot easily see or produce the usernames of given accounts.
- Usernames in Signal are protected using a custom Ristretto 25519 hashing algorithm and zero-knowledge proofs.
Upper Band = Mov(C, 20, E) + 2 * StDev(C, 20) Lower Band = Mov(C, 20, E) - 2 * StDev(C, 20)
In addition to other group attributes that are end-to-end encrypted (such as group names, group descriptions, and group avatars), the Signal service also doesn’t have access to any information about which accounts are part of a group, which accounts are admins in a group, which accounts can add new people to a group, which accounts can approve requests to join a group, or which accounts can send messages in a group.