Loop/Architecture/Context: Difference between revisions

Where IV is 12 bytes in length, and tag is 8 bytes (64 bits) in length.

Encryption consists of selecting a random 12-byte IV value. This IV, the plaintext JSON representation of the room context fields, and '''kRm''' are used as input to the AES-GCM encryption algorithm, which is configured to generate a 64-bit validation tag. The IV is then concatenated with the ciphertext and the validation tag. The resulting bytestring is Base64 encoded, and included as the "context.value" field in the appropriate Loop Server API call, alongside the wrapped room key '''kR''' and the algorithm name ("AES-GCM").

Decryption consists of Base64 decoding the "context" field, splitting off the first 12 bytes for use as an IV, and splitting off the final 8 bytes as the validation tag. These are then used as input to the AES-GCM decryption algorithm (along with '''kRm'''), the output of which is a JSON object containing fields that correspond to the various room context information fields.