SILMARILS: Information-Theoretic and Quantum-Secure Designated-Verifier Signatures
Pith reviewed 2026-05-20 23:19 UTC · model grok-4.3
The pith
SILMARILS builds transferable designated-verifier signatures from Shamir secret sharing over finite fields that stay secure for non-designated parties even against quantum attackers.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
SILMARILS realizes a transferable designated-verifier signature scheme achieving Jakobsson-Sako-Impagliazzo DV security, with EUF-CMA^¬DV security for all non-designated verifiers in both ROM and QROM, and a statistically secure signature protocol with simulation-based security and error 1/p in the three-party broadcast model.
What carries the argument
The minimal algebraic core over F_p together with perfect 2-out-of-2 Shamir secret sharing, which lets the designated verifier simulate indistinguishable transcripts while preserving unforgeability for everyone else.
If this is right
- Non-designated verifiers obtain EUF-CMA^¬DV security in both the random oracle model and the quantum random oracle model.
- The designated verifier can produce simulated accepting transcripts that remain indistinguishable from real ones even after publishing the receipt.
- In the three-party broadcast setting the protocol achieves simulation-based security with statistical error 1/p against quantum adversaries that have classical input-output access.
- Keys and signatures remain compact enough for lightweight authentication in blockchain environments.
Where Pith is reading between the lines
- The same secret-sharing core could be reused to build other lightweight multi-party primitives that require simulation by one designated party.
- Practical deployments would need to verify that true randomness sources remain quantum-resistant when feeding the algebraic core.
- If the broadcast model of Fitzi et al. holds in real networks, the three-party mode could support new forms of private multi-party authentication.
Load-bearing premise
The security reductions assume that 2-out-of-2 Shamir secret sharing over F_p remains perfectly secret and that true random bits stay hidden even when the adversary has quantum power but only classical input-output.
What would settle it
An explicit algorithm that, given only the public key and a transcript from a non-designated verifier, outputs a valid forgery that the designated verifier cannot simulate or a simulated transcript that an external party can distinguish from a real signature with probability noticeably larger than 1/p.
Figures
read the original abstract
SILMARILS is built from a minimal algebraic core over $\mathbb{F}_p$ using true randomness and perfect $2$-out-of-$2$ Shamir secret sharing. The framework supports both two-party and three-party modes. In the two-party setting, SILMARILS realizes a transferable designated-verifier (TDV) signature scheme. The designated verifier can simulate accepting transcripts indistinguishable from real ones, achieving Jakobsson-Sako-Impagliazzo DV security. The verifier may publish a receipt $r$ enabling public verification, yet even with $r$, no external party can tell whether a transcript was signed or simulated. As DV signatures permit simulation, standard EUF-CMA cannot hold for the designated verifier; instead, we prove $\mathsf{EUF\text{-}CMA}^{\neg\mathsf{DV}}$ security for all non-designated verifiers in both the random oracle model (ROM) and quantum random oracle model (QROM). In the three-party mode, adopting the broadcast model of Fitzi et al., we obtain a statistically secure signature protocol with simulation-based security and error $1/p$. We analyze security in the Pure IT model, the IT+ROM, and the QROM, extending the Fitzi et al. framework to quantum adversaries with classical I/O. Correctness, secrecy, transferability, and unforgeability for non-designated parties remain equivalent to simulation-based security. Thanks to its simple algebraic structure, SILMARILS offers very compact keys and signatures for the blockchain settings we target, where standardized PQC schemes are already more than sufficient. Our goal is not to compare SILMARILS with PQC, but to highlight its suitability for lightweight TDV authentication. A fair comparison with other DV schemes is omitted due to space and the complexity of aligning models.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript presents SILMARILS, a framework for transferable designated-verifier signatures constructed from 2-out-of-2 Shamir secret sharing over F_p with true randomness. In two-party mode it realizes Jakobsson-Sako-Impagliazzo DV security together with EUF-CMA^¬DV for non-designated verifiers in both ROM and QROM; in three-party mode, using an extension of the Fitzi et al. broadcast model to quantum adversaries with classical I/O, it yields a statistically secure signature protocol with simulation-based security and error 1/p. Security is analyzed in the pure IT, IT+ROM, and QROM models, with emphasis on compact keys and signatures for blockchain settings.
Significance. If the claimed reductions are correct, the construction supplies a lightweight, algebraically simple DV scheme that simultaneously achieves statistical simulation security, transferability, and QROM unforgeability for non-DV parties, offering a targeted alternative to general-purpose PQC signatures when only designated-verifier functionality is required.
major comments (2)
- [§5.3] §5.3 (QROM extension of Fitzi broadcast model): the manuscript asserts that perfect 2-out-of-2 Shamir secrecy composes with the broadcast model to preserve simulation-based security (error 1/p) against quantum adversaries restricted to classical I/O; however, no explicit bound is given on the distinguishing advantage when the adversary issues superposition queries to the random oracle while the underlying shares remain classical. This reduction step is load-bearing for the claimed equivalence between simulation security and EUF-CMA^¬DV for non-designated verifiers.
- [§6] §6 (Equivalence of security notions): correctness, secrecy, transferability, and unforgeability for non-DV parties are stated to be equivalent to simulation-based security, yet the argument relies on the QROM extension without exhibiting the concrete simulator or hybrid argument that handles classical message interfaces for quantum adversaries. This equivalence is central to the three-party security claim.
minor comments (2)
- The abstract claims 'very compact keys and signatures' but provides no concrete bit-lengths or comparison table; adding a small table of sizes for typical p would strengthen the blockchain suitability argument.
- Notation EUF-CMA^¬DV is used without a self-contained definition in the preliminaries; a short formal statement would improve readability.
Simulated Author's Rebuttal
We thank the referee for the thorough review and insightful comments on our manuscript. We are grateful for the opportunity to address the concerns raised regarding the QROM extension and the equivalence of security notions. Below, we provide point-by-point responses to the major comments and outline the revisions we will make to strengthen the presentation.
read point-by-point responses
-
Referee: [§5.3] §5.3 (QROM extension of Fitzi broadcast model): the manuscript asserts that perfect 2-out-of-2 Shamir secrecy composes with the broadcast model to preserve simulation-based security (error 1/p) against quantum adversaries restricted to classical I/O; however, no explicit bound is given on the distinguishing advantage when the adversary issues superposition queries to the random oracle while the underlying shares remain classical. This reduction step is load-bearing for the claimed equivalence between simulation security and EUF-CMA^¬DV for non-designated verifiers.
Authors: We appreciate the referee pointing out the need for an explicit bound. The composition relies on the perfect statistical secrecy of the 2-out-of-2 Shamir shares over F_p together with the classical I/O restriction in the extended Fitzi broadcast model. Superposition queries to the random oracle are handled via standard QROM simulation techniques that do not disturb the classical shares, yielding an overall distinguishing advantage of at most 1/p + negl(λ). To make the argument fully explicit, we will insert a detailed hybrid argument and the concrete bound into the revised §5.3. revision: yes
-
Referee: [§6] §6 (Equivalence of security notions): correctness, secrecy, transferability, and unforgeability for non-DV parties are stated to be equivalent to simulation-based security, yet the argument relies on the QROM extension without exhibiting the concrete simulator or hybrid argument that handles classical message interfaces for quantum adversaries. This equivalence is central to the three-party security claim.
Authors: We agree that exhibiting the concrete simulator and the hybrid argument would improve clarity and rigor. In the three-party mode the simulation-based security (error 1/p) implies the remaining properties via standard reductions that preserve classical message interfaces. We will add an explicit description of the simulator (which leverages the broadcast channel to produce consistent classical shares) together with the sequence of hybrids in the revised §6. revision: yes
Circularity Check
No circularity: security reductions rest on external primitives
full rationale
The paper constructs SILMARILS directly from the perfect secrecy of 2-out-of-2 Shamir secret sharing over F_p, true randomness, and the Fitzi et al. broadcast model (extended to QROM with classical I/O). Security claims for EUF-CMA^¬DV in ROM/QROM and simulation-based security (error 1/p) are derived via standard reductions to these independent assumptions rather than by redefining outputs in terms of inputs or fitting parameters. No self-definitional loops, fitted predictions, or load-bearing self-citations appear in the derivation chain; the algebraic core and model extensions remain self-contained against external benchmarks.
Axiom & Free-Parameter Ledger
free parameters (1)
- p
axioms (2)
- standard math Perfect secrecy of 2-out-of-2 Shamir secret sharing
- domain assumption Availability of true randomness
Reference graph
Works this paper leans on
-
[1]
Digital signature standard (DSS). Federal Information Processing Standard FIPS 186-1, National Institute of Standards and Technology, Gaithersburg, MD, USA (Dec 1998), https://csrc.nist.gov/pubs/fips/186-1/final, supersedes FIPS 186 (1996); Withdrawn January 27, 2000
work page 1998
-
[2]
Aardal, M.A., Adj, G., Aranha, D.F., Basso, A., Canales Martínez, I.A., Chávez- Saab, J., Corte-Real Santos, M., Dartois, P., De Feo, L., Duparc, M., Eriksen, J.K., Fouotsa, T.B., Gazzoni Filho, D.L., Hess, B., Kohel, D., Leroux, A., Longa, P., Maino, L., Meyer, M., Nakagawa, K., Onuki, H., Panny, L., Patranabis, S., Petit, C., Pope, G., Reijnders, K., Ro...
work page 2025
-
[3]
In: Applied Cryptography and Network Security
Amiri, R., Abidin, A., Wallden, P., Andersson, E.: Efficient unconditionally secure signatures using universal hashing. In: Applied Cryptography and Network Security. Lecture Notes in Computer Science, vol. 10892, pp. 143–162. Springer (2018)
work page 2018
-
[4]
Distributed Com- puting16, 165–175 (2003)
Aspnes, J.: Randomized protocols for asynchronous consensus. Distributed Com- puting16, 165–175 (2003)
work page 2003
-
[5]
In: Proceedings of the ACM Symposium on Principles of Distributed Computing
Ben-Or, M.: Another advantage of free choice: Completely asynchronous protocols. In: Proceedings of the ACM Symposium on Principles of Distributed Computing. pp. 27–30. ACM (1983)
work page 1983
-
[6]
Matryoshka: Fuzzing Deeply Nested Branches
Bernstein, D.J., Hülsing, A., Kölbl, S., Niederhagen, R., Rijneveld, J., Schwabe, P.: The SPHINCS+ signature framework. In: Proceedings of the 2019 ACM SIGSAC Conference on Computer and Communications Security. p. 2129–2146. Association for Computing Machinery, New York, NY, USA (2019).https://doi.org/10.1145/ 3319535.3363229,https://doi.org/10.1145/33195...
-
[7]
Beullens, W.: Breaking Rainbow takes a weekend on a laptop. In: Dodis, Y., Shrimp- ton, T. (eds.) Advances in Cryptology – CRYPTO 2022. pp. 464–479. Springer Na- ture Switzerland, Cham (2022).https://doi.org/10.1007/978-3-031-15979-4_ 16
-
[8]
Beullens, W., Chen, M.S., Ding, J., Gong, B., Kannwischer, M.J., Patarin, J., Peng, B.Y., Schmidt, D., Shih, C.J., Tao, C., Yang, B.Y.: UOV: Unbal- anced oil and vinegar — algorithm specifications and supporting documenta- tion (round 2). Tech. rep., NIST Post-Quantum Cryptography Project (Feb 2025), https://csrc.nist.gov/csrc/media/Projects/pqc-dig-sig/d...
work page 2025
-
[9]
Boneh, D.: Schnorr digital signature scheme. In: van Tilborg, H.C.A. (ed.) En- cyclopedia of Cryptography and Security. Springer, Boston, MA (2005).https: //doi.org/10.1007/0-387-23483-7_369
-
[10]
Boneh, D., Zhandry, M.: Secure signatures and chosen ciphertext security in a quantum computing world. In: CRYPTO 2013. Lecture Notes in Computer Science, vol. 8043, pp. 361–379. Springer (2013). https://doi.org/10.1007/ 978-3-642-40084-1_21
work page 2013
- [11]
-
[12]
In: Advances in Cryptology – CRYPTO ’90
Chaum, D., Roijakkers, S.: Unconditionally-secure digital signatures. In: Advances in Cryptology – CRYPTO ’90. Lecture Notes in Computer Science, vol. 537, pp. 206–214. Springer (1990) Title Suppressed Due to Excessive Length 29
work page 1990
-
[13]
Journal of Cryptology18, 191–217 (2005)
Considine, J., Fitzi, M., Franklin, M., Levin, L.A., Maurer, U., Metcalf, D.: Byzan- tine agreement given partial broadcast. Journal of Cryptology18, 191–217 (2005)
work page 2005
-
[14]
Courtois, N., Finiasz, M., Sendrier, N.: How to achieve a McEliece-based digital signature scheme. In: Boyd, C. (ed.) Advances in Cryptology – ASIACRYPT 2001. Lecture Notes in Computer Science, vol. 2248, pp. 157–174. Springer (2001)
work page 2001
-
[15]
In: Advances in Cryptology – EUROCRYPT ’99
Cramer, R., Damgård, I., Dziembowski, S., Hirt, M., Rabin, T.: Efficient multiparty computations secure against an adaptive adversary. In: Advances in Cryptology – EUROCRYPT ’99. Lecture Notes in Computer Science, vol. 1592, pp. 311–326. Springer (1999)
work page 1999
-
[16]
Cambridge University Press (2015)
Cramer, R., Damgård, I., Nielsen, J.: Secure Multiparty Computation and Secret Sharing. Cambridge University Press (2015)
work page 2015
-
[17]
Dang, Q., Moody, D.: Additional SLH-DSA parameter sets for limited-signature use cases. NIST Special Publication 800-230 (Initial Public Draft), National Insti- tute of Standards and Technology (Apr 2026).https://doi.org/10.6028/NIST. SP.800-230.ipd, https://doi.org/10.6028/NIST.SP.800-230.ipd, initial Public Draft
-
[18]
SIAM Journal on Computing12(4), 656–666 (1983)
Dolev, D., Strong, R.: Authenticated algorithms for Byzantine agreement. SIAM Journal on Computing12(4), 656–666 (1983)
work page 1983
-
[19]
Ducas, L., Kiltz, E., Lepoint, T., Lyubashevsky, V., Schwabe, P., Seiler, G., Stehlé, D.: CRYSTALS-Dilithium: A lattice-based digital signature scheme. IACR Transac- tions on Cryptographic Hardware and Embedded Systems2018(1), 238–268 (Feb 2018).https://doi.org/10.13154/tches.v2018.i1.238-268
-
[20]
https://github.com/ eternax-ai/silmarils-paper(2026), accessed: 2026-04-24
Eternax Labs: SILMARILS implementation repository. https://github.com/ eternax-ai/silmarils-paper(2026), accessed: 2026-04-24
work page 2026
-
[21]
SIAM Journal on Computing26(4), 873–933 (1997)
Feldman, P., Micali, S.: An optimal probabilistic protocol for synchronous Byzantine agreement. SIAM Journal on Computing26(4), 873–933 (1997)
work page 1997
-
[22]
Distributed Computing1(1), 26–39 (1986)
Fischer, M.J., Lynch, N.A., Merritt, M.: Easy impossibility proofs for distributed consensus problems. Distributed Computing1(1), 26–39 (1986)
work page 1986
-
[23]
Journal of the ACM32(2), 374–382 (1985)
Fischer, M.J., Lynch, N.A., Paterson, M.S.: Impossibility of distributed consensus with one faulty process. Journal of the ACM32(2), 374–382 (1985)
work page 1985
-
[24]
Journal of Cryptology18, 37–61 (2005)
Fitzi, M., Garay, J.A., Maurer, U., Ostrovsky, R.: Minimal complete primitive for secure multi-party computation. Journal of Cryptology18, 37–61 (2005)
work page 2005
-
[25]
In: Advances in Cryptology – EUROCRYPT 2002
Fitzi, M., Gisin, N., Maurer, U., Rotz, O.V.: Unconditional byzantine agreement and multi-party computation secure against dishonest minorities from scratch. In: Advances in Cryptology – EUROCRYPT 2002. Lecture Notes in Computer Science, vol. 2332, pp. 482–501. Springer (2002)
work page 2002
-
[26]
In: Advances in Cryptology – CRYPTO
Fitzi, M., Wolf, S., Wullschleger, J.: Pseudo-signatures, broadcast, and multiparty computation from correlated randomness. In: Advances in Cryptology – CRYPTO
- [27]
-
[28]
Fitzi, M., Hirt, M., Maurer, U.: Trading correctness for privacy in uncondi- tional multi-party computation. In: Krawczyk, H. (ed.) Advances in Cryptology — CRYPTO 1998. pp. 121–136. Springer Berlin Heidelberg, Berlin, Heidelberg (1998)
work page 1998
-
[29]
Fouque, P.A., Hoffstein, J., Kirchner, P., Lyubashevsky, V., Pornin, T., Prest, T., Ricosset, T., Seiler, G., Whyte, W., Zhang, Z.: Falcon: Fast-fourier lattice-based compact signatures over NTRU. https://research.ibm.com/publications/ falcon-fast-fourier-lattice-based-compact-signatures-over-ntru (Jan- uary 2020), iBM Research
work page 2020
-
[30]
In: Advances in Cryptology – ASIACRYPT
Hanaoka, G., Shikata, J., Zheng, Y., Imai, H.: Unconditionally secure digital signa- ture schemes admitting transferability. In: Advances in Cryptology – ASIACRYPT
- [31]
-
[32]
IEEE Access13, 9015–9031 (2025).https://doi.org/10.1109/ACCESS.2025.3526632
Iwamura, K., Kamal, A.A.A.M.: Secure user authentication with information theoretic security using secret sharing-based secure computation. IEEE Access13, 9015–9031 (2025).https://doi.org/10.1109/ACCESS.2025.3526632
-
[33]
In: Advances in Cryptology – EUROCRYPT ’96
Jakobsson, M., Sako, K., Impagliazzo, R.: Designated verifier proofs and their applications. In: Advances in Cryptology – EUROCRYPT ’96. Lecture Notes in Computer Science, vol. 1070, pp. 143–154. Springer (1996)
work page 1996
-
[34]
Johnson, D., Menezes, A., Vanstone, S.: The elliptic curve digital signature algorithm (ECDSA). Int. J. Inf. Secur.1(1), 36–63 (Aug 2001).https://doi.org/10.1007/ s102070100002,https://doi.org/10.1007/s102070100002
-
[35]
Jonsson, J., Kaliski, B.: Public-key cryptography standards (pkcs) #1: Rsa cryp- tography specifications version 2.1. RFC 3447, Internet Engineering Task Force (IETF) (Feb 2003),https://datatracker.ietf.org/doc/html/rfc3447
work page 2003
-
[36]
Journal of Computer and System Sciences75(2), 91–112 (2009)
Katz, J., Koo, C.Y.: On expected constant-round protocols for byzantine agreement. Journal of Computer and System Sciences75(2), 91–112 (2009)
work page 2009
-
[37]
Krotou, A.: Shamir’s secret sharing (sss) for quantum-safe data storage (October 2025), https://vault12.com/learn/advanced-crypto-security/cryptography/ quantum-safe-data/, vault12
work page 2025
-
[38]
ACM Trans- actions on Programming Languages and Systems4(3), 382–401 (1982)
Lamport, L., Shostak, R., Pease, M.: The byzantine generals problem. ACM Trans- actions on Programming Languages and Systems4(3), 382–401 (1982)
work page 1982
-
[39]
Lamport, L.: Constructing digital signatures from a one way function. Tech. Rep. CSL-98, SRI International, Computer Science Laboratory, Menlo Park, California (Oct 1979),https://lamport.azurewebsites.net/pubs/dig-sig.pdf
work page 1979
- [40]
-
[41]
Deep Space Network Progress Report44, 114–116 (Jan 1978), https://ui
McEliece, R.J.: A public-key cryptosystem based on algebraic coding theory. Deep Space Network Progress Report44, 114–116 (Jan 1978), https://ui. adsabs.harvard.edu/abs/1978DSNPR..44..114M, provided by the SAO/NASA As- trophysics Data System
work page 1978
-
[42]
Merkle, R.: A certified digital signature. In: CRYPTO. pp. 218–238. Springer (1989)
work page 1989
-
[43]
Cambridge University Press, 10th anniversary edition edn
Nielsen, M.A., Chuang, I.L.: Quantum Computation and Quantum Information. Cambridge University Press, 10th anniversary edition edn. (2010)
work page 2010
-
[44]
Journal of the ACM27(2), 228–234 (1980)
Pease, M., Shostak, R., Lamport, L.: Reaching agreement in the presence of faults. Journal of the ACM27(2), 228–234 (1980)
work page 1980
-
[45]
In: 24th Annual Symposium on Foundations of Computer Science (FOCS)
Rabin, M.O.: Randomized Byzantine generals. In: 24th Annual Symposium on Foundations of Computer Science (FOCS). pp. 403–409. IEEE Computer Society (1983)
work page 1983
-
[46]
Shamir, A.: How to share a secret. Commun. ACM22(11), 612–613 (Nov 1979). https://doi.org/10.1145/359168.359176
-
[47]
Cambridge University Press (2023)
Tyagi, H., Watanabe, S.: Information-theoretic Cryptography. Cambridge University Press (2023)
work page 2023
-
[48]
Unruh, D.: Universally composable quantum multi-party computation. In: EURO- CRYPT 2010. Lecture Notes in Computer Science, vol. 6110, pp. 486–505. Springer (2010).https://doi.org/10.1007/978-3-642-13190-5_25
-
[49]
In: Advances in Cryptology — EUROCRYPT 2015
Unruh, D.: Non-interactive zero-knowledge proofs in the quantum random oracle model. In: Advances in Cryptology — EUROCRYPT 2015. LNCS, vol. 9057, pp. 755–784. Springer (2015)
work page 2015
-
[50]
Watrous, The Theory of Quantum Information, Cambridge University Press, 2018
Watrous, J.: The Theory of Quantum Information. Cambridge University Press (2018).https://doi.org/10.1017/9781316848142
-
[51]
Communi- cations in Mathematical Physics347(1), 291–313 (2016).https://doi.org/10
Winter, A.: Tight uniform continuity bounds for quantum entropies. Communi- cations in Mathematical Physics347(1), 291–313 (2016).https://doi.org/10. 1007/s00220-016-2609-8 Title Suppressed Due to Excessive Length 31
work page 2016
-
[52]
In: 2012 IEEE 53rd Annual Symposium on Foundations of Computer Science
Zhandry, M.: How to construct quantum random functions. In: 2012 IEEE 53rd Annual Symposium on Foundations of Computer Science. pp. 679–687 (2012). https://doi.org/10.1109/FOCS.2012.37
-
[53]
In: Boldyreva, A., Micciancio, D
Zhandry, M.: How to record quantum queries, and applications to quantum in- differentiability. In: Boldyreva, A., Micciancio, D. (eds.) Advances in Cryptology – CRYPTO 2019. Lecture Notes in Computer Science, vol. 11693, pp. 239–268. Springer (2019)
work page 2019
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.