Impossibility

Status	Statement	Tags
	Fully quantum time-lock puzzles Open in the fully quantum case. Settled by the source paper when the generator is classical and the solver quantum, and when the generator is quantum and the solver classical under perfect completeness; a classical-query attack on the remaining cell would prove a simulation conjecture. 5 open	Quantum Query Complexity Quantum Random Oracle Model Time Lock Puzzlesqromimpossibility
	CAQB key agreement, imperfect completeness Open. Settled for perfect completeness by the source paper’s Theorem 3.1; the argument’s final step uses perfect completeness in a way that no known weakening survives, and the paper’s Simulation-Conjecture barrier does not cover this party structure. 5 open	Quantum Key Agreement Quantum Query Complexity Quantum Random Oracle Modelqromimpossibility
	SK-DEPIR from One-Way Functions Stated by the source as its own conjecture and proved for two-round passive-server schemes. Its main theorem – that any crypto oracle can be stripped out of a SK-DEPIR and replaced by a one-way function – is stated conditionally on this, so the conjecture is the single remaining hypothesis between that compiler and a clean statement that no idealized generic primitive helps. 4 open	Black Box Separations One Way Functions Private Information Retrievalimpossibility
	No expanding weak quadratic PRGs Open: whether every family of quadratic Λ(n)-bounded polynomials at stretch m ≥ n^{1+ε} admits an efficient distinguisher from the same evaluations plus bounded independent noise; the paper proves only the i.i.d.-nice special case (Theorem 2) and reports, without proof, that no degree-two candidate survives its attacks experimentally. 3 open	Average Case Hardness Pseudorandom Generatorsimpossibility
	No Self-Reduction for LSN Conjecture 5.20 of the source. It proves no random self-reduction exists from an arbitrary worst-case QNCP instance into LSN, naming exchange symmetry between code and error as the obstruction, and proves the tableau-randomizing barrier conditionally on the scrambling gap being polynomially related to eps. It is explicit that this is not an impossibility for random self-reductions in general. 4 open	Average Case Hardness Learning Parity With Noise Quantum Information Stabilizer Codesimpossibilityadaptation (ai)
	No 2-element split NILPs A submitted construction gives a two-element split NILP for Boolean circuit satisfiability in the plain generic Type-III bilinear-group model; proof review and formalization remain open. 2 open	Generic Group Model Proof Size Lower Bounds Snarksimpossibilityresearch-solved
	OWFs are black-box useless for key agreement Open in the general case, which the paper names as the central open problem left by its work. Settled for three restricted protocol classes: constant-query perfect, constant-round constant-query imperfect, and Merkle-type. 5 open	Black Box Separations Key Agreement One Way Functionsotherimpossibility
	No round-optimal pairing-free blind signature Open for a polynomial query budget. The impossibility is proved when User_2 and Verify together make O(log lambda) random-oracle queries, including when oracle outputs contain group elements; the superpolynomial message space hypothesis is retained. 5 open	Black Box Separations Blind Signatures Generic Group Model Signature Schemesggmimpossibilityadaptation (ai)
	Computationally unique VDFs in the ROM Resolved. Guan, Riazanov and Yuan, Breaking Verifiable Delay Functions in the Random Oracle Model (ePrint 2024/766, CRYPTO 2025), prove that no VDF in the parallel ROM can have completeness and computational uniqueness and be sigma-sequential for sigma a fixed polynomial in the security parameter and the Setup/Verify query counts – their Theorem 5.1, which in fact covers general (not just perfect) completeness error, strictly more than this conjecture asked for. The proof is human-authored and published; it has not yet been independently re-derived by this site or formalized in Lean. 3 open	Black Box Separations Random Oracle Model Verifiable Delay Functionsromimpossibilityresearch-solved