Replay Attacks and Defenses Against Cross-shard Consensus in Sharded Distributed Ledgers
summary
Shows a concrete pre-accept replay attack that replays recorded shard messages to double-spend across shards by exploiting message races and missing session binding; attacker can be the client or a passive network manipulator. Builds Biscuit: adds object sequence numbers as session IDs, forces output shards to lock a dummy object so every shard participates in phase one, and uses a transaction manager to aggregate messages. Provides a proof sketch, open‑source implementation, and shows the fix prevents the described replays.
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chapters (7)
- 0:00Introduction
- 1:39Sharding and cross-shard
- 4:59Replay attack analysis
- 12:46OmniLedger comparison
- 16:04Root causes and mitigation
- 19:07The Biscuit protocol
- 26:55Conclusion and Q&A
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