#TRILLIAN S.M.S SOFTWARE#

This ensures that values from the past can’t be covertly modified without being detected. If they both agree on the map head hash, the sender knows it has received the right public key.Īs with all verifiable data structures, it’s important they are monitored for consistency over time rather than at a single point in time. The strength of Key Transparency is that two different apps can ensure they are accessing exactly the same map structure as long as they can compare a single value, the map head hash.īoth the sender and the receiver query for the receiver’s public key, while verifying the map.

Users can check they’re seeing the same public key

Key server - a server which implements the Key Transparency pattern as a Trillian personality.Public key - the public part of the keys used by other users to encrypt messages to the user.For example, a user has a WhatsApp account after they receive an SMS from WhatsApp proving they control the number. Account - the link between the app and the users' phone number.Phone number - used by other users to identify the person.

#TRILLIAN S.M.S SOFTWARE#

App - like Signal or Threema (Key Transparency supports any client software that links a username to a public key.).

If Bob’s app saw the same map head hash as Alice’s app, they can be sure they have the same public key for Alice. This is currently not defined by Key Transparency.īob has Alice’s mobile number and wants to send a message with the app.īob’s app asks the key server for Alice’s public key from her mobile number, and receives Alice’s public key and a signed map head hash.īob’s app cryptographically verifies the map by calculating a chain of hashes from the public key up to a single map head hash.īob’s app compares the calculated map head hash with the one received via the gossip network. The app “gossips” each map head hash it observes to other users by a gossip network. If another user can calculate the same map head hash, it proves both users were querying the same map. The app cryptographically verifies the map by calculating a chain of hashes from the public key up to a single map head hash. The app ensures that the public key matches its local key. It returns the public key along with additional data that can be used to verify the map. The key server calculates the hash of the mobile number and uses it to locate the public key in the log-backed map. The key server calculates a special hash on the mobile number and stores the public key in a “log-backed map” - a data structure which links mobile numbers to public keys.Īlice’s app asks the key server for its own public key. When Bob wants to send Alice an encrypted message:Īlice’s app uploads her mobile number and public key to the key server. (Key Transparency is more flexible, supporting any type of username and multiple public keys per username.) To illustrate the way key discovery works in Key Transparency, we refer to a messaging app that uses mobile numbers to identify users. Specifically, Key Transparency uses a log-backed map which is a verifiable map combined with a verifiable log. Key Transparency uses Trillian’s experimental map mode, rather than the more common log mode. Key Transparency uses Trillian’s Experimental Map Mode

Reduce the impact of a compromised server or legal demands for surveillance.Record a history of a user’s public keys that can’t be altered, ensuring misbehaviour by the key server will be recorded, even if it is temporary.Increase the difficulty of an attacker performing a man-in-the-middle attack.

Provide a shared global view of public keys - everyone should see the same public key for a given username.Automate user discovery of end-to-end encryption keys.

Trillian s.m.s