matrix-spec/api/server-server/examples/unsigned_pdu.json

{
    "room_id": "!UcYsUzyxTGDxLBEvLy:example.org",
    "sender": "@alice:example.com",
    "origin": "example.com",
    "event_id": "$a4ecee13e2accdadf56c1025:example.com",
    "origin_server_ts": 1404838188000,
    "type": "m.room.message",
    "prev_events": [
        [
            "$af232176:example.org",
            {"sha256": "abase64encodedsha256hashshouldbe43byteslong"}
        ]
    ],
    "content": {
        "key": "value"
    }
}