Ability to revoke/block own key

Would be nice to be able to broadcast messages like "this key was compromised" and/or "no further messages from this key are valid". This would address both the problem of private key already being compromised and add ability to lock the site forever (whether because there's a danger of key being compromised in the future or just because site is intended to be static).

When a node receives "compromised" message, it should stop accepting any further updates from the key and it would be nice to also mark data as potentially replaced by third-parties. When a node receives "no further updates" message, it does the same without marking data as compromised, and should also still react on "compromised" message (in order to prevent attacker to first replace content and then freeze it).

Potential drawback: this would add ability to kill all services based on private keys being public. But those are already susceptible to any kind of attack, so personally i don't think it's that bad. Also, it should be possible to also add "exception" feature if these are considered important enough.

PS: I think this was mentioned before on the network, but i couldn't find an issue here.

ファイル、テスト、またはエントリポイントは指定されていません。まず、プロトコルの主要な検証および更新受け入れ経路を特定し、次に署名付き失効メッセージがどのように表現され、伝播されるかを判断してください。完了の条件は、侵害済みおよび以後の更新なしのメッセージが後続の更新を確実にブロックし、データマーキングにおける記載された区別を維持し、順序付けと例外のテストを含むことです。

索引モデルが issue の本文から書いたものです。