Splitting Secrets for Encrypted Backups
summary
Proposes two deployable designs that split backup keys so one compromised component cannot leak many users: a three-cloud enclave design that uses OPRF-based password-protected secret sharing across AMD/Intel/AWS enclaves and a modified, rollback-resistant Raft to prevent enclave rollback attacks (rollback component is implemented and in production; multi-enclave use is not deployed due to cost). An alternative, Chorus, shards secrets across client committees for 100M clients (assumes ≤10% compromise, ≤50% offline), with clients chosen ~every 4 months (28s work when chosen, ~7s/month, 13.2MB, ~0.38% battery); server cost is ~10× the enclave approach.
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chapters (11)
- 0:00Secret splitting for backups
- 1:07PIN backups brute force risks
- 3:36Avoiding privacy failure points
- 6:47Splitting secrets across enclaves
- 9:18Rollback-resistant enclave consensus
- 11:06Splitting secrets across devices
- 13:16Client committee design
- 16:49Rotating client committees
- 19:16Architecture trade-offs
- 20:40Key takeaways
- 21:23Q&A
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