Censorship resistance in the KMS

[kvinwang]

Summary

There is a discussion about ensuring censorship resistance in the KMS de-registration process, particularly focused on preventing scenarios where a vulnerable KMS instance continues operating because it's being prevented from seeing de-registration transactions.

Problem Statement

A critical security vulnerability scenario:

1. A vulnerability is discovered in KMS and the corresponding measurement is de-registered on-chain
2. Existing KMS instances are blocked from processing new blocks by an attacker
3. The KMS instances never see the de-registration transaction and continue operating
4. Attackers have unlimited time to extract the root secret
5. The de-registration effectively becomes useless

Proposed Solutions

On-chain Interaction Requirements

• KMS must interact with the chain at startup and periodically thereafter
• Limit the number of actions allowed without forcing an on-chain interaction
• Require a random nonce to appear on-chain periodically

Trusted Time Sources Alternative

• Use NTS or similar trusted time sources

Considerations

• On-chain interactions are costly and involved
• Need to ensure NTS cannot be replayed or delayed in ways that defeat verification
• Verification is only as reliable as the trusted time source