I went to an Encryption and Key Management in AWS presentation at the pop-up loft in San Francisco, and they explained how their KMS system is built on shared H

I went to an Encryption and Key Management in AWS presentation at the pop-up loft in San Francisco, and they explained how their KMS system is built on shared Hardware Security Modules (HSMs) that are tamper evident and have hardcoded logging. So any decryption event is logged and you'd have to physically break into the HSMs to prevent a log entry (and thus have to replace lots of equipment). This basically meant that it would cost millions of dollars to secretly decrypt something where the user wouldn't be able to see a log of it. It's basically a "porcupine defense" where governments won't bother asking for secret decryption since it would cost so much money. They specifically designed the infrastructure to be extremely expensive to hide any log altering. It also means that governments will more likely try compromising the targets system first, rather than send a secret decryption order to Amazon. EDIT: Additionally, since the HSMs are shared, any physical tampering would require them to notify and migrate all the other users on that HSM that are under regulations (HIPAA, PCI DSS, etc.). AWS would charge a lot of money for this sort of migration.