Separation

Status	Statement	Tags
	CPA PKE, Quantumly Broken The first item in the source’s Open Problems section. It builds counterexamples for PRFs, CPA-secure symmetric-key encryption, MACs, signatures and CCA-2-secure public-key encryption, all classically secure under LWE via black-box reductions and all quantumly broken with two or three classical queries. CPA-secure public-key encryption is the case its technique cannot reach, and it says why. 4 open	Black Box Separations Learning With Errors Quantum Cryptographyseparation
	Four-party NIKE, quadratic, Maurer’s model Open. Achieved in Shoup’s generic group model by the source paper (Construction 9, Theorem 10); in Maurer’s model the paper’s own O(n^2) attack sets a ceiling that a construction would meet exactly, and nothing is known about reaching it. 5 open	Generic Group Model Non Interactive Key Exchangeggmseparation
	1+1 adaptively secure lattice threshold signature Resolved. Oriole (Jiang, Wee, Zhu, ePrint 2026/793, posted April 2026, a month after Tweed) gives a lattice-based threshold signature with exactly this shape – two rounds, only the second message-dependent, adaptive security against T-1 corruptions with no erasures, from MSIS and MLWE in the ROM – verified here directly against the paper’s PDF (Definition of adp-TS-sUF-4 in its Figure 4, and the Theorem 2 + Theorem 3 reduction chain to MSIS), not just its abstract. The proof is human-written and published, but not yet independently re-verified line-by-line by this site, nor formalized in Lean.	Learning With Errors Threshold Signatures Tight Reductionsromseparationresearch-solved
	SBP Collision Resistance Posed as a displayed Open Question and called a central open challenge. The source gives an efficient online collision finder for small kappa and an overlap-gap-based online lower bound for a different, randomized activation – introduced precisely because the SBP’s own collision space resists a first-moment analysis. For very large kappa collisions become trivial. The middle window is reached by neither technique. 4 open	Average Case Hardness Collision Resistant Hashing Overlap Gap Property Planted Constraint Satisfactionseparation
	Conflict Checkable Codes Beyond Half-Singleton Theorem 1.8 proves k <= (n-d+2)/2 for codes that are both comparison-based and local-to-global consistent. Theorem 1.3 gives an almost-MDS conflict checkable code at k >= n-d+1-epsilon which bypasses that bound, but it is neither comparison-based nor known to be local-to-global consistent. The conjecture names comparison-basedness as the culprit. It already holds at d = n-1. 4 open	Code Based Cryptography Locally Testable Codes Threshold Secret Sharingseparationadaptation (ai)
	Erasing real-or-random vs Boneh–Zhandry Open: whether erasing real-or-random security implies Boneh-Zhandry security. The reverse non-implication is proved only in the quantum random oracle model, and this direction is one of six non-implications the source paper conjectures and does not prove. 5 open	Quantum Cryptography Quantum Encryption Notionsseparation
	No key agreement from GC-OWF Open for round complexity growing with the security parameter. Proved in full for two messages, which is public-key encryption; the constant-round extension is sketched in the paper’s appendix without a theorem, its security half deferred to the PKE proof. 5 open	Black Box Separations Garbled Circuits Key Agreementotherseparationadaptation (ai)
	One erasing challenge vs many embedding learns Open: whether a single erasing two-ciphertext challenge query, with classical learning queries, implies security against polynomially many embedding-model superposition learning queries. One of six non-implications the source paper conjectures, and on its own account the one that would close the most remaining cells. 5 open	Quantum Cryptography Quantum Encryption Notionsseparation
	Standard real-or-random vs embedding two-ciphertext Open: whether one standard-oracle real-or-random challenge query implies one embedding-model two-ciphertext challenge query, with classical learning queries on both sides. Both notions are singleton classes in the source’s classification, and this is one of six non-implications it conjectures. 5 open	Quantum Cryptography Quantum Encryption Notionsseparation
	OWFs are black-box helpful for CRHFs Open in both directions. Two relaxations — distributional and class-reduction helpfulness — are proved conditional on the Simon-oracle amplification conjecture; neither yields the universal auxiliary primitive the full statement needs. 4 open	Black Box Separations Collision Resistant Hashing One Way Functionsotherseparation
	PKE from constant-noise planted k-XOR Open: whether public-key encryption can be based on the hardness of planted k-XOR with a linear number of equations and a constant noise rate, as a single assumption. The survey poses it as one of two closing open questions and does not return to it; every combinatorial scheme it surveys needs sub-constant noise.	Average Case Hardness Planted Constraint Satisfactionseparationbarrier (ai)
	Certifying no small non-expanding set Open: whether the non-existence of a small non-expanding set in a random unbalanced bipartite graph admits a nondeterministic certificate that is sound and complete on average, at the parameters the ABW cryptosystem uses. The survey poses it as one of two closing open questions, takes no position, and does not return to it.	Average Case Hardness Expander Graphsseparation
	XOR as a Weak 2-Immunizer The single unresolved cell in the source’s own table: XOR fails as a strong 2-immunizer under Alekhnovich, a bilinear pairing fails as a weak one under SXDH, a random oracle succeeds even with auxiliary input. The weak case for XOR is left open with a conjectured answer and a concrete route to it. 4 open	Backdoored Primitives Black Box Separations Pseudorandom Generatorsseparationadaptation (ai)