matrix-doc/event-schemas/examples/m.key.verification.key

{
    "type": "m.key.verification.key",
    "content": {
        "transaction_id": "S0meUniqueAndOpaqueString",
        "key": "fQpGIW1Snz+pwLZu6sTy2aHy/DYWWTspTJRPyNp0PKkymfIsNffysMl6ObMMFdIJhk6g6pwlIqZ54rxo8SLmAg"
    }
}