fix(mpc-tls): domain-separate per-consumer KOS instances - #2
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Each RCOT consumer now gets its own KOS instance (deadlock fix), but they all reuse one global delta. Give each logical consumer a distinct `instance_id` salt so the instances are domain-separated, closing the shared-delta leak flagged in review of tlsnotary/tlsn#1173. Ids are assigned explicitly per consumer so prover and verifier stay matched (sender id N pairs with receiver id N); proxy mode uses a single fixed id. Depends on the mpz salt (AdamDawidKrol/mpz#2), pulled via the [patch] block.
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Wires the per-instance KOS salt (AdamDawidKrol/mpz#2) into tlsn to close the shared-
deltaleak flagged in review of tlsnotary/tlsn#1173.The deadlock fix gives each RCOT consumer its own KOS instance, but they all reuse one global
delta. With several same-deltaKOS instances and no domain separation, a malicious party can reuse the same base OT across two of them; the instances then derive identical transcripts and the correlation leaksdelta(base-OT-reuse / PRG-collision — the mechanism sinui0 flagged). This is a genuinely multi-instance issue: it cannot arise with a single instance, so it's specific to the deadlock fix's fan-out. Each logical consumer (mpc, zk, and the three mpc-tls senders + their paired receivers) now gets a distinctinstance_id, assigned explicitly so prover and verifier stay matched (sender id N ↔ receiver id N). Proxy mode uses a single fixed id (Block::ZERO).Not addressed by this change (orthogonal): the KOS single-instance selective-failure leakage is a property of KOS itself, present with or without the deadlock fix, and domain separation does not affect it. The fan-out only amplifies it (more same-
deltainstances = more selective-failure queries per session). See the draft PoC in #3.The
[patch]block points mpz at the salt rev from #2.Verified:
test_mpcandtest_proxy(--ignored) pass end-to-end.Stacked on: AdamDawidKrol/mpz#2.