SafeSwiss uses state-of-the-art asymmetric cryptography based on Elliptic Curve Cryptography (ECC) in general and on the “Box” model of the NaCl Networking and Cryptography Library in concrete to protect (encrypt and authenticate) messages between sender and receiver, as well as the communication between the app and the servers. SafeSwiss encryption code is open to independent audits.
There are two layers of encryption: end-to-end layer between the conversation participants, and an additional layer to protect against eavesdropping of the connection between the app and the servers. The latter is necessary to ensure that an adversary who captures network packets (e.g. on a public wireless network) cannot even learn who is logging in and sending a message to whom.
All SafeSwiss message encryption and decryption happens directly on the device, and the user has control over the key exchange. This guarantees that no third party — not even the server operators — can decrypt the content of any messages.