LBAC: Lattice-based Anonymous Credential Based on the zk-creds Paradigm

GUO Xian; GU Tengfei; JIA Wenjuan; CHENG Yudan; FANG Junli; FENG Tao

doi:10.11999/JEIT260718

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GUO Xian, GU Tengfei, JIA Wenjuan, CHENG Yudan, FANG Junli, FENG Tao. LBAC: Lattice-based Anonymous Credential Based on the zk-creds Paradigm[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT260718

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GUO Xian, GU Tengfei, JIA Wenjuan, CHENG Yudan, FANG Junli, FENG Tao. LBAC: Lattice-based Anonymous Credential Based on the zk-creds Paradigm[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT260718

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LBAC: Lattice-based Anonymous Credential Based on the zk-creds Paradigm

doi: 10.11999/JEIT260718 cstr: 32379.14.JEIT260718

School of Computer Science and Artificial Intelligence, Lanzhou University of Technology, 730050, China

Funds: The National Natural Science Foundation of China (61461027), The Natural Science Foundation of Gansu Province (26JRRA528, 20JR5RA467)

Received Date: 2026-06-01
Accepted Date: 2026-09-15
Rev Recd Date: 2026-09-14

Available Online: 2026-09-22

Abstract

Abstract

Objective With the growing deployment of digital identity systems, protecting user privacy and reducing excessive identity disclosure has become a key requirement.Existing digital identity frameworks, such as eIDAS 2.0 and W3C Verifiable Credentials, rely on cryptographic mechanisms to enable selective disclosure. However, current anonymous credential schemes face two major limitations. First, most existing schemes are built on classical number-theoretic assumptions, which are vulnerable to Shor’s quantum algorithm and cannot resist future quantum computing attacks. Second, high-performance privacy-preserving schemes generally follow the Signature with Efficient Protocol (SEP) paradigm, which requires identity issuers to adopt specific nonstandard signature primitives and results in poor compatibility with existing identity infrastructures. Although the zk-creds paradigm improves compatibility by using general-purpose zero-knowledge proofs to encapsulate standard credentials, existing implementations mainly depend on pairing-based proof systems, such as Groth16, and therefore lack post-quantum security. Meanwhile, lattice-based solutions introduce large proof sizes and high communication overhead due to the complexity of high-dimensional matrix operations. Therefore, developing an anonymous credential scheme that maintains compatibility with existing credential systems while achieving post-quantum security remains an important challenge. Methods A lattice-based anonymous credential scheme named LBAC (Lattice-Based Anonymous Credentials) is proposed under the zk-creds paradigm. The scheme adds a zero-knowledge proof layer between users and verifiers to decouple presentation from the original credential issuance.Existing digital credentials are directly used as private inputs, and no modification or interaction with credential issuers is required. A hybrid proof framework based on the lattice-based LaBRADOR interactive proof system is constructed. First, a random masking mechanism based on Ajtai commitments is introduced to achieve zero-knowledge and non-interactive proof generation. The rejection sampling method is adopted to blind the original witness, and the Fiat-Shamir heuristic is applied to convert the interactive protocol into a non-interactive zero-knowledge argument. Second, the Sumcheck protocol is introduced as a proof compressor to reduce the verification complexity of arithmetic circuits generated from standard signature verification. By transforming large-scale circuit satisfiability statements into smaller polynomial evaluation and dot-product proof tasks, the computational overhead of LaBRADOR is reduced. Finally, based on the design concept of the Crescent scheme, the improved LaBRADOR proof generation process is divided into an offline Prepare phase and an online Show phase. The computationally intensive operations, including Sumcheck compression and the initial D–1 rounds of recursive folding, are completed during the Prepare phase, where intermediate states and base vectors are stored locally. During the Show phase, the prover only performs lightweight lattice vector re-randomization using a fresh nonce and cached data, enabling efficient credential presentation with multi-show unlinkability. Results and Discussions The security properties of the LBAC scheme are analyzed and proven under the random oracle model. Experimental evaluations are conducted on an Ubuntu 20.04 platform equipped with an Intel Xeon Platinum 8352V processor. The results demonstrate that the Prepare-Show architecture effectively improves credential presentation efficiency. By transferring computationally intensive operations to the Prepare phase, the Show phase achieves a presentation time of 5.27 ms, which is lower than that of existing quantum-resistant schemes based on Ligero and remains competitive with classical non-quantum-resistant schemes (Fig. 4). For a circuit scale of 2²⁰ constraints, the generated proof size is 50.17 kB, showing lower communication overhead than existing quantum-resistant alternatives (Fig. 5). Unlike conventional quantum-resistant schemes whose proof sizes increase rapidly with statement complexity, LBAC maintains a logarithmic proof size through the recursive amortization mechanism of the modified LaBRADOR system. The verification time is 621 ms, which is acceptable considering the post-quantum security provided by the scheme and the fact that verification is generally performed on powerful servers. This overhead can be further reduced through batch verification techniques and GPU acceleration for Number Theoretic Transform (NTT). Conclusions A post-quantum secure anonymous credential scheme for existing digital credentials is proposed by integrating the zk-creds paradigm with an optimized LaBRADOR proof system and the Sumcheck protocol. The proposed framework improves compatibility with existing credential systems while providing post-quantum security, compact proof sizes, and efficient credential presentation. The correctness, presentation unforgeability, and anonymity with multi-show unlinkability are formally proven. Future research will focus on simulation extractability, hardware-based device binding, and traceability mechanisms to further improve security in adaptive adversarial environments and support credential management while preserving privacy.
- Anonymous credentials,
- Lattice-based cryptography,
- Quantum-resistant security,
- Zero-knowledge proofs,
- Privacy preserving

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References(30)

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