Formal Verification of Probing Security via Conditional Independence
Pith reviewed 2026-05-25 03:19 UTC · model grok-4.3
The pith
Noninterference properties of masked algorithms can be verified by reducing them to conditional independence in Lilac separation logic.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Noninterference of masked algorithms is equivalent to a form of conditional independence, so the Lilac separation logic for conditional independence can be used to verify probing security, supported by additional proof rules that the authors introduce and apply to example algorithms.
What carries the argument
Lilac, the separation logic for conditional independence, linked to noninterference through an explicit correspondence plus several new proof rules that simplify verification of probing security.
If this is right
- Probing security checks for masked code can reuse any existing Lilac proofs or tools developed for conditional independence.
- The supplied proof rules reduce the manual effort needed to establish noninterference for typical masking schemes.
- Verification becomes compositional because separation logic naturally handles independent components of a masked circuit.
- The method applies directly to the example algorithms shown in the paper, confirming it scales at least to small masked implementations.
Where Pith is reading between the lines
- The same correspondence could extend verification to other leakage models beyond probing if conditional independence can be restated for those models.
- Integration with existing program logics for cryptographic code would allow end-to-end security arguments that include both functional correctness and side-channel resistance.
- Automated tactics for the new rules could turn the approach into a practical tool rather than a manual proof exercise.
Load-bearing premise
The Lilac logic plus the new proof rules accurately capture the probabilistic noninterference semantics of masked algorithms without missing side conditions.
What would settle it
A masked algorithm that is noninterfering by the standard probabilistic definition but cannot be proved secure in Lilac, or an algorithm that is proved secure in Lilac yet leaks information under probing.
Figures
read the original abstract
Side-channel attacks are a major threat to the security of cryptosystems. Masking is a widely used countermeasure against such attacks, but proving the security of masked algorithms is error-prone without formal verification. In this work, we propose a novel approach to formal verification of noninterference properties of masked algorithms based on probabilistic separation logic. By establishing a connection between noninterference and conditional independence, we show how noninterference can be verified using Lilac, a separation logic for conditional independence. We also provide several proof rules that facilitate the verification of probing security and demonstrate their application to example algorithms.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper claims that noninterference properties of masked algorithms (for probing security against side-channel attacks) can be verified by establishing a connection to conditional independence and using the existing Lilac separation logic, augmented with several new proof rules whose application is demonstrated on example algorithms.
Significance. If the embedding of noninterference into Lilac is shown to be sound and the new rules are proven correct with respect to the probabilistic semantics of masked circuits, the work would supply a reusable formal tool for a practically important verification task in cryptography.
major comments (1)
- [Abstract] The central claim rests on the unexamined assumption that Lilac's conditional-independence rules plus the new proof rules correctly capture the probabilistic noninterference semantics without introducing unsoundness or requiring additional side conditions on mask distributions; no soundness argument, semantic embedding, or example derivation is available for inspection.
Simulated Author's Rebuttal
We thank the referee for their review. We address the major comment on the soundness of the embedding below.
read point-by-point responses
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Referee: [Abstract] The central claim rests on the unexamined assumption that Lilac's conditional-independence rules plus the new proof rules correctly capture the probabilistic noninterference semantics without introducing unsoundness or requiring additional side conditions on mask distributions; no soundness argument, semantic embedding, or example derivation is available for inspection.
Authors: The abstract is necessarily concise. The full manuscript examines the assumption in detail: Section 2 recalls the probabilistic semantics of masked circuits and defines noninterference; Section 3 proves the equivalence between noninterference and conditional independence (under the standard uniform independent mask distribution) and shows that this equivalence licenses direct application of Lilac's rules; Section 4 introduces the new probing-specific rules and proves them sound with respect to the same semantics, with no extra side conditions required. Concrete derivations appear in Section 6. We can add an explicit reference to these sections in a revised abstract if the editor prefers. revision: no
Circularity Check
No significant circularity identified
full rationale
The paper establishes a semantic connection between noninterference and conditional independence, then uses the existing Lilac logic plus new proof rules to verify probing security on masked algorithms. No equations, definitions, or claims in the provided abstract reduce a derived result to a fitted parameter, self-citation chain, or renamed input by construction. The central claim (connection + rules) retains independent content outside any self-referential loop.
Axiom & Free-Parameter Ledger
axioms (1)
- standard math Lilac separation logic is sound for reasoning about conditional independence in probabilistic programs.
Reference graph
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Therefore, we have JM ′K(a1, a2) =JM ′K(a1, a′ 2), which is a contradiction
By Lemma B.6, we have(Y 1)∗νx1,x2 =JMK(x 1, x2)for almost all(x 1, x2), i.e., for any(x 1, x2)∈ {(a 1, a2),(a 1, a′ 2)}. Therefore, we have JM ′K(a1, a2) =JM ′K(a1, a′ 2), which is a contradiction. For the (⇐=) direction of Theorem V .1, the key lemma is the following. Lemma B.10.Let∆ =X 1 :A 1, . . . , Xn :A n be a context,∆⊢M:GBbe an APPL program, andZ∈...
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IfC i j ∈ Oandj < t, theni∈I∩J
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[46]
Ifi < j,C i j ∈ O, andi < k≤j < t, then(i, k)∈K Q
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IfC i j ∈ O,k < i,j < t, and(k, i)∈K Q, thenk, i∈Iandk, i∈J
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[48]
IfQ i,j ∈ O, then(i, j)∈K Q
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[49]
IfR i,j ∈ O, then(i, j)∈K Q,i∈I, andj∈J
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If(i, j)∈K Q andS i,j ∈ O, theni, j∈Iandi, j∈J
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[51]
IfC i t ∈ Oand there existsj < twithC i j ∈ O, thenV i ⊆K Q ∪K S
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Here,V i ={(k, i)|k < i} ∪ {(i, k)|i < k}is the indices of the free variables ing i t(Q,S)
IfC i t ∈ Oand there is noj < twithC i j ∈ O, thenV i \(K Q ∪K S)̸=∅. Here,V i ={(k, i)|k < i} ∪ {(i, k)|i < k}is the indices of the free variables ing i t(Q,S). Condition 9 follows because |Vi ∩(K Q ∪K S)| ≤ |O \C t|<|V i|=t. Vi ∩(K Q ∪K S) =V i ∩ {(i, j)|Q i,j ∈Q∨R i,j ∈ O ∨S i,j ∈ O} ∪ {(k, i)|k < i, C k j ∈ O, j < t} ∪ {(i, k)|i < k, C k j ∈ O, j < t}...
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