{
    "type": "m.key.verification.start",
    "content": {
        "from_device": "BobDevice1",
        "transaction_id": "S0meUniqueAndOpaqueString",
        "method": "m.sas.v1",
        "key_agreement_protocols": ["curve25519"],
        "hashes": ["sha256"],
        "message_authentication_codes": ["hkdf-hmac-sha256"],
        "short_authentication_string": ["decimal", "emoji"]
    }
}