Subcodes of Lambda-Gabidulin Codes for Compact-Ciphertext Cryptography
Pith reviewed 2026-05-10 04:34 UTC · model grok-4.3
The pith
Random subcodes of classical Gabidulin codes yield the smallest ciphertexts in MinRank-based encryption at 128-, 192-, and 256-bit security.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Among the parameter sets considered in this work, the most compact ciphertexts are obtained from random subcodes of classical Gabidulin codes. At the 128-, 192-, and 256-bit security levels, the resulting LGS-Niederreiter instances achieve the smallest ciphertext sizes among the compared schemes, while maintaining competitive public-key sizes.
What carries the argument
Random subcodes of classical Gabidulin codes, built from generator matrices to sidestep nontrivial algebraic invariants, and deployed as the underlying codes in MinRank-based Niederreiter encryption.
If this is right
- LGS-Niederreiter schemes deliver the smallest ciphertexts among the compared rank-metric schemes at 128-, 192-, and 256-bit security.
- Public-key sizes stay competitive with existing constructions.
- Subspace subcodes of lambda-Gabidulin codes relate to those of classical Gabidulin codes by coordinate-wise scaling, yielding explicit cardinality bounds.
- When extension degree equals length, Gabidulin subspace subcodes admit an explicit description via linearized polynomials for encoding and dimension.
Where Pith is reading between the lines
- Focusing on carefully chosen random subcodes rather than full Gabidulin codes may offer a general route to size reductions in other rank-metric cryptographic constructions.
- The generator-matrix method for avoiding invariants could be tested on additional families of rank-metric codes to check if similar compactness gains appear.
- If the MinRank hardness assumption holds for these parameters, the schemes provide concrete candidates for bandwidth-sensitive post-quantum applications.
Load-bearing premise
The random subcodes of Gabidulin codes avoid nontrivial algebraic invariants exploitable by attacks, and the MinRank problem stays computationally hard for the chosen parameters.
What would settle it
An efficient attack that recovers the secret from a public key of one of the proposed LGS-Niederreiter instances at the stated security levels, or a practical solver for the corresponding MinRank instances.
Figures
read the original abstract
This paper investigates subcodes of lambda-Gabidulin codes, viewed as rank-metric analogues of generalized Reed--Solomon codes, and their applications to compact-ciphertext cryptosystems. We first analyze subspace and generalized subspace subcodes of lambda-Gabidulin codes and relate them to corresponding subcodes of classical Gabidulin codes through coordinate-wise scaling. This relation yields cardinality bounds and structural properties for these families. When the extension degree equals the code length, we further characterize Gabidulin subspace subcodes in terms of linearized polynomials, which gives an explicit description of their encoding and dimension. We also study the matrix images of these subcodes over the base field through their stabilizer and annihilator algebras, showing that subspace restrictions may preserve nontrivial algebraic invariants despite the loss of extension-field linearity. Motivated by these results, we propose a generator-matrix-based construction of random subcodes designed to avoid such invariants. This construction is then used to design McEliece-like and Niederreiter-like encryption schemes in the MinRank setting. Among the parameter sets considered in this work, the most compact ciphertexts are obtained from random subcodes of classical Gabidulin codes. At the 128-, 192-, and 256-bit security levels, the resulting $\mathsf{LGS}$-Niederreiter instances achieve the smallest ciphertext sizes among the compared schemes, while maintaining competitive public-key sizes.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. This paper analyzes subspace and generalized subspace subcodes of lambda-Gabidulin codes, relating them to subcodes of classical Gabidulin codes via coordinate-wise scaling to obtain cardinality bounds and structural properties. When the extension degree equals code length, it characterizes Gabidulin subspace subcodes via linearized polynomials for explicit encoding and dimension. It studies matrix images through stabilizer and annihilator algebras, showing that subspace restrictions can preserve nontrivial algebraic invariants. Motivated by this, the paper proposes a generator-matrix-based random subcode construction to avoid such invariants and applies it to MinRank-based McEliece-like and Niederreiter-like encryption schemes. The central claim is that, among considered parameters, random subcodes of classical Gabidulin codes yield LGS-Niederreiter instances with the smallest ciphertext sizes at the 128-, 192-, and 256-bit security levels while maintaining competitive public-key sizes.
Significance. If the random subcodes indeed trivialize the relevant algebras (so that only generic MinRank attacks apply) and the security estimates hold, the work provides a concrete improvement in ciphertext compactness for code-based post-quantum encryption. The algebraic analysis of invariants via stabilizer/annihilator algebras is a useful structural contribution that can inform future subcode designs. The explicit parameter comparisons and constructions add practical value if the security assumptions are verified.
major comments (2)
- [Parameter tables and security analysis] Parameter tables and security analysis section: no explicit computation of the dimensions of the stabilizer or annihilator algebras is reported for the concrete random generator matrices used in the LGS-Niederreiter parameter sets at 128/192/256-bit security. This verification is load-bearing for the claim that only generic MinRank attacks apply and thus for the asserted ciphertext-size superiority.
- [Random subcode construction] Random subcode construction (following the algebra analysis): the proposal is motivated by the observation that subspace subcodes may retain invariants, yet the text provides neither a proof that the randomness suffices to trivialize the algebras nor empirical checks (e.g., algebra-dimension computations) on the specific instances whose performance is highlighted. Without this, the security-level labels and cross-scheme ranking rest on an unverified assumption.
minor comments (2)
- [Abstract] The acronym LGS is used in the abstract and claims without an immediate expansion or forward reference to its definition as Lambda-Gabidulin Subcodes.
- [Analysis of subcodes] Notation for the scaling relation between lambda-Gabidulin and classical Gabidulin subcodes could be illustrated with a small explicit example to improve readability of the cardinality bounds.
Simulated Author's Rebuttal
We thank the referee for the careful reading and for highlighting the need for explicit verification of the algebraic invariants in our concrete parameter sets. We address the major comments point by point below. We will revise the manuscript to include the requested empirical checks on algebra dimensions, which will strengthen the security analysis without altering the core claims.
read point-by-point responses
-
Referee: [Parameter tables and security analysis] Parameter tables and security analysis section: no explicit computation of the dimensions of the stabilizer or annihilator algebras is reported for the concrete random generator matrices used in the LGS-Niederreiter parameter sets at 128/192/256-bit security. This verification is load-bearing for the claim that only generic MinRank attacks apply and thus for the asserted ciphertext-size superiority.
Authors: We agree that the current manuscript lacks explicit computations of the stabilizer and annihilator algebra dimensions for the specific random generator matrices appearing in the 128-, 192-, and 256-bit security parameter tables. This verification is indeed important to confirm that only generic MinRank attacks apply. In the revised version we will add these computations (performed over the base field for each listed generator matrix) and report the resulting dimensions. Preliminary calculations on the chosen random instances indicate that both algebras are trivial, consistent with the assumption used for the security estimates and ciphertext-size comparisons. revision: yes
-
Referee: [Random subcode construction] Random subcode construction (following the algebra analysis): the proposal is motivated by the observation that subspace subcodes may retain invariants, yet the text provides neither a proof that the randomness suffices to trivialize the algebras nor empirical checks (e.g., algebra-dimension computations) on the specific instances whose performance is highlighted. Without this, the security-level labels and cross-scheme ranking rest on an unverified assumption.
Authors: The generator-matrix-based random subcode construction is motivated by the preceding algebraic analysis showing that certain structured subcodes can preserve nontrivial invariants. We do not claim or provide a general proof that random selection always trivializes the algebras, as establishing such a probabilistic statement rigorously would require additional combinatorial arguments outside the scope of the present work. However, we acknowledge the absence of empirical checks on the concrete instances. In the revision we will include algebra-dimension computations for the exact random matrices used in the highlighted LGS-Niederreiter parameter sets, thereby supplying the missing empirical support for the security assumptions underlying the ciphertext-size rankings. revision: partial
- A formal proof that random selection of generator matrices suffices to trivialize the stabilizer and annihilator algebras with overwhelming probability
Circularity Check
No significant circularity; derivation is self-contained
full rationale
The paper first derives cardinality bounds and structural properties (including stabilizer/annihilator algebras) directly from the definitions of lambda-Gabidulin codes, subspace subcodes, and their matrix images over the base field. It then proposes a generator-matrix random subcode construction explicitly motivated by those derived properties to avoid nontrivial invariants. Encryption instances are instantiated from this construction, with security levels assigned via the external MinRank hardness assumption and generic attack costs on the chosen parameters. No step equates a derived quantity to its own input by definition, renames a fitted value as a prediction, or reduces the central claim to a self-citation chain; the comparative ciphertext-size claims follow from explicit parameter tables and standard MinRank cost estimates.
Axiom & Free-Parameter Ledger
axioms (1)
- domain assumption The MinRank problem remains hard for the chosen parameters and subcode constructions.
Reference graph
Works this paper leans on
-
[1]
Bilinear forms over a finite field, with applications to coding theory,
P. Delsarte, “Bilinear forms over a finite field, with applications to coding theory,”J. Comb. Theory, Ser. A, vol. 25, no. 3, pp. 226–241, 1978
work page 1978
-
[2]
Theory of codes with maximum rank distance,
`E. M. Gabidulin, “Theory of codes with maximum rank distance,”Problemy Peredachi Informatsii, vol. 21, no. 1, pp. 3–16, 1985
work page 1985
-
[3]
Ideals over a non-commutative ring and their applications to cryptography,
E. M. Gabidulin, A. V . Paramonov, and O. V . Tretjakov, “Ideals over a non-commutative ring and their applications to cryptography,” in Advances in Cryptology - EUROCRYPT’91, ser. Lecture Notes in Comput. Sci., no. 547, Brighton, Apr. 1991, pp. 482–489. 27
work page 1991
-
[4]
R. J. McEliece,A Public-Key System Based on Algebraic Coding Theory. Jet Propulsion Lab, 1978, pp. 114–116, dSN Progress Report 44
work page 1978
-
[5]
Generic decoding in the sum-rank metric,
S. Puchinger, J. Renner, and J. Rosenkilde, “Generic decoding in the sum-rank metric,”IEEE Transactions on Information Theory, vol. 68, no. 8, pp. 5075–5097, 2022
work page 2022
-
[6]
Properties of codes with the rank metric,
M. Gadouleau and Z. Yan, “Properties of codes with the rank metric,” inProceedings of IEEE Global Telecommunications Conference (GLOBECOM), 2006
work page 2006
-
[7]
Rank-metric codes and their applications,
H. Bartz, L. Holzbaur, H. Liu, S. Puchinger, J. Renner, and A. Wachter-Zeh, “Rank-metric codes and their applications,”Foundations and Trends in Communications and Information Theory, vol. 19, no. 3, pp. 390–546, 2022
work page 2022
-
[8]
Severely denting the Gabidulin version of the McEliece public key cryptosystem,
J. K. Gibson, “Severely denting the Gabidulin version of the McEliece public key cryptosystem,”Designs, Codes and Cryptography, vol. 6, no. 1, pp. 37–45, 1995
work page 1995
-
[9]
A new structural attack for GPT and variants,
R. Overbeck, “A new structural attack for GPT and variants,” inMycrypt, ser. Lecture Notes in Comput. Sci., vol. 3715, 2005, pp. 50–63
work page 2005
-
[10]
Structural attacks for public key cryptosystems based on Gabidulin codes,
——, “Structural attacks for public key cryptosystems based on Gabidulin codes,”J. Cryptology, vol. 21, no. 2, pp. 280–301, 2008
work page 2008
-
[11]
Improved cryptanalysis of rank metric schemes based on Gabidulin codes,
A. Otmani, H. T. Kalachi, and S. Ndjeya, “Improved cryptanalysis of rank metric schemes based on Gabidulin codes,”Designs, Codes and Cryptography, vol. 86, no. 9, pp. 1983–1996, 2018
work page 1983
-
[12]
Extension of Overbeck’s attack for Gabidulin-based cryptosystems,
A.-L. Horlemann-Trautmann, K. Marshall, and J. Rosenthal, “Extension of Overbeck’s attack for Gabidulin-based cryptosystems,” Designs, Codes and Cryptography, vol. 86, pp. 319–340, 2018
work page 2018
-
[13]
On the failure of the smart approach of the GPT cryptosystem,
H. T. Kalachi, “On the failure of the smart approach of the GPT cryptosystem,”Cryptologia, vol. 46, no. 2, pp. 167–182, 2022
work page 2022
-
[14]
Designs, Codes and Cryptography73(2), 641–666 (2014).https://doi
A. Couvreur, P. Gaborit, V . Gauthier-Uma ˜na, A. Otmani, and J.-P. Tillich, “Distinguisher-based attacks on public-key cryptosystems using Reed-Solomon codes,”Des. Codes Cryptogr., vol. 73, no. 2, pp. 641–666, 2014. [Online]. Available: http://dx.doi.org/10.1007/s10623-014-9967-z
-
[15]
On subfield subcodes of modified Reed–Solomon codes,
P. Delsarte, “On subfield subcodes of modified Reed–Solomon codes,”IEEE Transactions on Information Theory, vol. 21, no. 5, pp. 575–576, 1975
work page 1975
-
[16]
A survey on code-based cryptography,
V . Weger, N. Gassner, and J. Rosenthal, “A survey on code-based cryptography,” 2022
work page 2022
-
[17]
On subcodes of codes in rank metric,
E. M. Gabidulin and P. Loidreau, “On subcodes of codes in rank metric,” inProceedings. International Symposium on Information Theory, 2005. ISIT 2005.IEEE, 2005, pp. 121–123
work page 2005
-
[18]
Properties of subspace subcodes of Gabidulin codes,
——, “Properties of subspace subcodes of Gabidulin codes,”Advances in Mathematics of Communications, vol. 2, no. 2, p. 147, 2008
work page 2008
-
[19]
Rank subcodes in multicomponent network coding,
E. M. Gabidulin and N. I. Pilipchuk, “Rank subcodes in multicomponent network coding,”Problems of information transmission, vol. 49, no. 1, pp. 40–53, 2013
work page 2013
-
[20]
List decodability of random subcodes of Gabidulin codes,
S. Liu, C. Xing, and C. Yuan, “List decodability of random subcodes of Gabidulin codes,”IEEE Transactions on Information Theory, vol. 63, no. 1, pp. 159–163, 2016
work page 2016
-
[21]
Gabidulin matrix codes and their application to small ciphertext size cryptosystems,
T. P. Berger, P. Gaborit, and O. Ruatta, “Gabidulin matrix codes and their application to small ciphertext size cryptosystems,” inProgress in Cryptology–INDOCRYPT 2017: 18th International Conference on Cryptology in India, Chennai, India, December 10-13, 2017, Proceedings 18. Springer, 2017, pp. 247–266
work page 2017
-
[22]
Two modifications for Loidreau’s code-based cryptosystem,
W. Guo and F.-W. Fu, “Two modifications for Loidreau’s code-based cryptosystem,”Applicable Algebra in Engineering, Communication and Computing, vol. 35, no. 5, pp. 647–665, 2024
work page 2024
-
[23]
A new Gabidulin-like code and its application in cryptography,
T. S. C. Lau and C. H. Tan, “A new Gabidulin-like code and its application in cryptography,” inInternational Conference on Codes, Cryptology, and Information Security. Springer, 2019, pp. 269–287
work page 2019
-
[24]
Security assessment of the LG cryptosystem,
´E. Burle, H. T. Kalachi, F. L. Metouke, and A. Otmani, “Security assessment of the LG cryptosystem,”Applicable Algebra in Engineering, Communication and Computing, vol. 37, no. 1, pp. 187–198, 2026
work page 2026
-
[25]
MinRank Gabidulin encryption scheme on matrix codes,
N. Aragon, A. Couvreur, V . Dyseryn, P. Gaborit, and A. Vin c ¸otte, “MinRank Gabidulin encryption scheme on matrix codes,” in International Conference on the Theory and Application of Cryptology and Information Security. Springer, 2024, pp. 68–100
work page 2024
-
[26]
Topics in matrix analysis cambridge university press cambridge,
R. Horn and C. R. Johnson, “Topics in matrix analysis cambridge university press cambridge,”UK Google Scholar, 1991
work page 1991
-
[27]
On subfield subcodes of modified Reed-Solomon codes (corresp.),
P. Delsarte, “On subfield subcodes of modified Reed-Solomon codes (corresp.),”IEEE Transactions on Information Theory, vol. 21, no. 5, pp. 575–576, 2003
work page 2003
-
[28]
Subfield subcodes and trace codes,
H. Stichtenoth, “Subfield subcodes and trace codes,”Algebraic Function Fields and Codes, pp. 311–326, 2009
work page 2009
-
[29]
Subspace subcodes of Reed-Solomon codes,
M. Hattori, R. J. McEliece, and G. Solomon, “Subspace subcodes of Reed-Solomon codes,”IEEE Transactions on Information Theory, vol. 44, no. 5, pp. 1861–1880, 2002
work page 2002
-
[30]
On the security of subspace subcodes of Reed–Solomon codes for public key encryption,
A. Couvreur and M. Lequesne, “On the security of subspace subcodes of Reed–Solomon codes for public key encryption,”IEEE Transactions on Information Theory, vol. 68, no. 1, pp. 632–648, 2021
work page 2021
-
[31]
Generalized subspace subcodes in the rank metric,
O. Ndiaye, P. A. Kidoudou, and H. T. Kalachi, “Generalized subspace subcodes in the rank metric,”arXiv preprint arXiv:2301.12523, 2023
- [32]
-
[33]
Theory of non-commutative polynomials,
O. Ore, “Theory of non-commutative polynomials,”Annals of mathematics, vol. 34, no. 3, pp. 480–508, 1933
work page 1933
-
[34]
On a special class of polynomials,
——, “On a special class of polynomials,”Transactions of the American Mathematical Society, vol. 35, no. 3, pp. 559–584, 1933
work page 1933
-
[35]
B. R. McDonald, “Finite rings with identity,”(No Title), 1974
work page 1974
-
[36]
Improved key attack on the minrank encryption scheme based on matrix codes,
A. Porwal, A. Wachter-Zeh, and P. Loidreau, “Improved key attack on the minrank encryption scheme based on matrix codes,”Cryptology ePrint Archive, 2025
work page 2025
-
[37]
J.-C. Faugere, F. Levy-dit Vehel, and L. Perret, “Cryptanalysis of minrank,” inAnnual International Cryptology Conference. Springer, 2008, pp. 280–296
work page 2008
-
[38]
The computational complexity of some problems of linear algebra,
J. F. Buss, G. S. Frandsen, and J. O. Shallit, “The computational complexity of some problems of linear algebra,”Journal of Computer and System Sciences, vol. 58, no. 3, pp. 572–596, 1999
work page 1999
-
[39]
Design principles for HFEv-based multivariate signature schemes,
A. Petzoldt, M.-S. Chen, B.-Y . Yang, C. Tao, and J. Ding, “Design principles for HFEv-based multivariate signature schemes,” in Advances in Cryptology–ASIACRYPT 2015: 21st International Conference on the Theory and Application of Cryptology and Information Security, Auckland, New Zealand, November 29–December 3, 2015, Proceedings, Part I 21. Springer, 20...
work page 2015
-
[40]
Improved cryptanalysis of uov and rainbow,
W. Beullens, “Improved cryptanalysis of uov and rainbow,” inAnnual International Conference on the Theory and Applications of Cryptographic Techniques. Springer, 2021, pp. 348–373
work page 2021
-
[41]
Cryptanalysis of the TTM cryptosystem,
L. Goubin and N. T. Courtois, “Cryptanalysis of the TTM cryptosystem,” inAdvances in Cryptology—ASIACRYPT 2000: 6th International Conference on the Theory and Application of Cryptology and Information Security Kyoto, Japan, December 3–7, 2000 Proceedings 6. Springer, 2000, pp. 44–57
work page 2000
-
[42]
Matrix multiplication via arithmetic progressions,
D. Coppersmith and S. Winograd, “Matrix multiplication via arithmetic progressions,” inProceedings of the nineteenth annual ACM symposium on Theory of computing, 1987, pp. 1–6
work page 1987
-
[43]
Improvement of algebraic attacks for solving superdetermined minrank instances,
M. Bardet and M. Bertin, “Improvement of algebraic attacks for solving superdetermined minrank instances,” inInternational Conference on Post-Quantum Cryptography. Springer, 2022, pp. 107–123
work page 2022
-
[44]
M. Bros, “Algebraic cryptanalysis and contributions to post-quantum cryptography based on error-correcting codes in the rank-metric,” Ph.D. dissertation, Universit ´e de Limoges, 2022
work page 2022
-
[45]
Revisiting algebraic attacks on minrank and on the rank decoding problem,
M. Bardet, P. Briaud, M. Bros, P. Gaborit, and J.-P. Tillich, “Revisiting algebraic attacks on minrank and on the rank decoding problem,” Designs, Codes and Cryptography, vol. 91, no. 11, pp. 3671–3707, 2023
work page 2023
-
[46]
Hybrid subsupport guessing: A new hybrid technique for the rank decoding problem,
H. Beeloo-Sauerbier Couv ´ee, A. Wachter-Zeh, and V . Weger, “Hybrid subsupport guessing: A new hybrid technique for the rank decoding problem,” inPost-Quantum Cryptography, M. Bardet and R. Niederhagen, Eds. Cham: Springer Nature Switzerland, 2026, pp. 130–155
work page 2026
-
[47]
A minrank-based encryption scheme \a la alekhnovich-regev,
T. Debris-Alazard, P. Gaborit, R. Neveu, and O. Ruatta, “A minrank-based encryption scheme \a la alekhnovich-regev,”arXiv preprint arXiv:2510.07584, 2025
-
[48]
A NP-complete problem in coding theory with application to code based cryptography,
T. P. Berger, C. T. Gueye, and J. B. Klamti, “A NP-complete problem in coding theory with application to code based cryptography,” in International Conference on Codes, Cryptology, and Information Security. Springer, 2017, pp. 230–237
work page 2017
-
[49]
Protocoles cryptographiques bas ´es sur les codes correcteurs d’erreur en m ´etrique rang,
A. Vinc ¸otte, “Protocoles cryptographiques bas ´es sur les codes correcteurs d’erreur en m ´etrique rang,” Ph.D. dissertation, Universit ´e de Limoges, 2025
work page 2025
-
[50]
Classic McEliece: conservative code-based cryptography,
D. J. Bernstein, T. Chou, T. Lange, I. von Maurich, R. Misoczki, R. Niederhagen, E. Persichetti, C. Peters, P. Schwabe, N. Sendrier et al., “Classic McEliece: conservative code-based cryptography,”NIST submissions, vol. 1, no. 1, pp. 1–25, 2017
work page 2017
-
[51]
The blockwise rank syndrome learning problem and its applications to cryptography,
N. Aragon, P. Briaud, V . Dyseryn, P. Gaborit, and A. Vin c ¸otte, “The blockwise rank syndrome learning problem and its applications to cryptography,” inInternational Conference on Post-Quantum Cryptography. Springer, 2024, pp. 75–106
work page 2024
-
[52]
C. A. Melchor, N. Aragon, P. Barreto, S. Bettaieb, L. Bidoux, O. Blazy, J.-C. Deneuville, P. Gaborit, S. Gueron, T. G ¨uneysuet al., “Bike,”First round submission to the NIST post-quantum cryptography call, 2017
work page 2017
-
[53]
RQC revisited and more cryptanalysis for rank-based cryptography,
L. Bidoux, P. Briaud, M. Bros, and P. Gaborit, “RQC revisited and more cryptanalysis for rank-based cryptography,”IEEE Transactions on Information Theory, 2023. 29
work page 2023
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.