Reusable Authentication Schemes

Updated 10 January 2026

Reusable authentication schemes are cryptographic protocols that allow the repeated use of credentials across multiple sessions, domains, or applications while mitigating risks like phishing and credential leakage.
They employ diverse primitives such as PAKE, key recycling, quantum public-key methods, and attribute-based credentials to achieve tailored security guarantees with minimal cumulative leakage.
Practical deployments focus on high usability and efficiency through optimized protocols and rigorous security analyses, ensuring forward secrecy, selective disclosure, and robust privacy protection.

Reusable authentication schemes are cryptographic protocols and architectures allowing principals to repeatedly prove legitimacy or perform secure actions across multiple sessions, domains, or applications, without requiring the establishment of fresh credentials or repeated secret disclosure. By supporting single-setup or multi-use credentials—typically based on secrets, keys, or cryptographic material—these schemes balance security, usability, and privacy, addressing threats such as phishing, credential leakage, and credential exhaustion. Contemporary research spans augmentations of password-based schemes, key recycling primitives, quantum identification, and anonymous single sign-on, with rigorous security analyses and practical deployments.

1. Foundational Models of Reusability

Reusable authentication encompasses diverse technical paradigms unified by their persistence of credential material across multiple uses, without excessive risk of cross-session compromise. These include:

Augmented PAKE with out-of-band device: The ZeroTwo protocol requires a master secret $p$ chosen once per device, reused for all service domains by calculating $x = H(I_u\|\!I_s\|\!p)$ (Chuat et al., 2019). The derived verifier $v = g^x$ ensures each server stores an independent non-invertible record, preventing cross-site attack vectors.
Key-recycled message authentication: Wegman–Carter authentication with $\epsilon$ -AXU $_2$ hash families permits secure reuse of the hash-selection key $k_1$ across $n$ rounds, with overall distinguishing advantage at most $n\epsilon$ and per-message one-time pad freshness (Portmann, 2012).
Quantum public-key identification: In this paradigm, Alice's private key is a vector $\mathbf x$ , and public key is $s$ copies of the quantum state tensor product $|\psi_{x_j}\rangle$ ; both are reusable up to $r$ sessions, with unconditional security bounded by $P_{\rm break} \le r(1 - c/(2r+1)^2)^s$ (Ioannou et al., 2011).
Attribute-based credential (ABC) architectures: An ABC credential is issued once, stored in an eID wallet, and can support repeated proofs of selective attributes using randomized signatures (e.g., BBS $^+$ ), with unlinkability guaranteed by per-use randomization (Hansen et al., 2024).

2. Protocol Mechanics and Algorithms

Reusable authentication protocols leverage cryptographic primitives enabling credential reuse without forfeiting security:

Zero-Knowledge Augmented PAKE: The server stores verifier $v$ $v$ , never learning the master secret $p$ $p$ . Authentication proceeds by a two-phase PAKE with out-of-band MAC-authenticated message flows, supporting explicit transaction signing and multiple domains (Chuat et al., 2019):
- Registration: $v = g^x$ sent to server.
- Authentication: Users input only $I_u$ ; smartphone computes $x$ and responds via secure MAC.
- Authorization: HMAC-based proofs with session keys.
Key Recycling via AXU $_2$ /ASU $_2$ Hash Families: Wegman–Carter-style schemes employ per-message one-time pads and a fixed hash function key $k_1$ , with synchronization preventing accept/reject-induced leakage (Portmann, 2012).

Protocol	Credential Reuse Mechanism	Leakage Control
ZeroTwo (Chuat et al., 2019)	$p$ persisted across domains; $x$ per domain	Zero-knowledge proofs over $p$
Wegman–Carter (Portmann, 2012)	$k_1$ (hash key) reused, per-message OTP	Leakage $\le n\epsilon$ if $\epsilon$ -AXU $_2$

Quantum Public-Key Authentication: The system supports $r$ sessions per key, relying on quantum operations to preserve information-theoretic security and prevent cumulative leakage (Ioannou et al., 2011).
Anonymous SSO with Proxy Re-Verification: A single user ticket encodes tags for multiple services; tags validated by designated verifiers, with proxy mechanisms for service outages, and central verifiers for audit (Han et al., 2018). Credentials—BBS $^+$ -style signatures—allow repeated validation without linkage.

3. Security Analysis and Guarantees

Robust security foundations target threats from passive/active adversaries, cross-session linkage, impersonation, and credential exhaustion:

Zero-Knowledge Assurance: ZeroTwo provides formal zero-knowledge security proofs—server views are simulatable without $p$ , and session keys are CDH-hard to distinguish from random (Chuat et al., 2019).
Composable Security in Key Recycling: Abstract cryptography framework quantifies distinguishability between real and ideal resources ( $\epsilon$ -close in statistical distance), exposing subtle leakage when accept/reject is observed, and showing $n$ -round reuse remains secure as long as $n\epsilon$ is negligible (Portmann, 2012).
Quantum Unconditional Security: Security parameters $r$ and $s$ allow arbitrary reduction of impersonation probability; $s=O(r^2\log(r/\varepsilon))$ ensures $P_{\text{break}}<\varepsilon$ against any adversary (Ioannou et al., 2011).
Selective Disclosure, Unlinkability, Unforgeability: ABC schemes (Hansen et al., 2024) achieve formal unforgeability (signature security), unlinkability (randomization per session), and minimal attribute leakage (by zero-knowledge proofs).
Anonymous Aggregation and Authentication: Chu-ko-nu leverages zero-knowledge (Schnorr + pairing-based) proofs for anonymous client authentication in federated learning, achieving formal dropout resilience, forward/backward secrecy, and resistance to impersonation (Cui et al., 2024).

4. Usability, Deployability, and Performance

Contemporary designs strive for high usability alongside rigorous security metrics:

ZeroTwo: Registration is a one-time QR scan; subsequent logins require only identity input and smartphone approval. Mobile cryptographic operations ( $\sim$ 20ms/side) and total communication ($200$–$600$B) are competitive with traditional PAKE but eliminate password typing (Chuat et al., 2019).
Key Recycling: For $\epsilon=2^{-80}$ , Wegman–Carter protocol allows $10^6$ authentic rounds with cumulative error $<10^{-8}$ (Portmann, 2012).
Quantum Public-Key: Communication overhead incurs $s$ qubits per session, but information-theoretic security justifies cost in quantum infrastructures (Ioannou et al., 2011).
Anonymous SSO: ASSO scheme achieves sub-500ms per tag validation in practical pairing-based implementing, and supports proxy-recovery for verifier outages (Han et al., 2018).
Attribute-Based Credentials: Issuance typically incurs $10$–$20$ms; selective disclosure proofs $5$–$10$ms; proof verification $15$–$30$ms, compatible with web/mobile environments (Hansen et al., 2024).
Federated Learning Aggregation: Chu-ko-nu reduces aggregation time by 21.0–63.1% over state-of-the-art, with the key-sharing overhead amortized; per-round communication and cryptographic work are minimized (Cui et al., 2024).

5. Privacy-Preserving and Anonymous Extensions

Privacy-centric reusable schemes deploy advanced cryptography to reach anonymity, unlinkability, and minimal disclosure:

Attribute-Based Credentials: Zero-knowledge selective disclosure ensures data controllers only learn the necessary subset of user attributes for the specific request, preserving anonymity across repeated interactions (Hansen et al., 2024).
ASSO with Proxy Re-Verification: Verification tags are validated only by designated verifiers; collusion or centralization (except by CA) cannot link user sessions. Proxy re-verification confers robustness, while central authority can deanonymise for regulatory or audit requirements (Han et al., 2018).
Anonymous Authentication in Federated Learning: Chu-ko-nu’s NIZK stack hides client identities and credentials while supporting authentication to prevent Sybil attacks and fraudulent aggregation, essential in privacy-critical collaborative settings (Cui et al., 2024).

6. Limitations, Parameterization, and Future Directions

Practical considerations, parameter setting, and open research directions shape deployment and evolution:

Parameter Choices: In key-recycling, tag length $|T|$ and $\epsilon$ must be set such that $n\epsilon$ remains negligible even under high-frequency reuse (Portmann, 2012). Quantum schemes must fix $r$ (max uses) per key, with $s$ scaled for desired error bounds (Ioannou et al., 2011).
Hardware and Trust Requirements: Many schemes assume secure enclaves, biometric sensors, or trusted modules; some require telco or CA trust anchors (Chuat et al., 2019, Aghav et al., 2014, Han et al., 2018).
Heavy Cryptographic Operations: Bilinear pairing-based protocols may strain low-end hardware; research continues into lattice-based alternatives and optimized zero-knowledge proof systems to enable post-quantum resistance and minimize resource costs (Han et al., 2018).
Extensibility: Reusable authentication primitives generalize to privacy-preserving SSO, federated learning, multi-service or cross-domain identity, and verifiable delegation (proxy re-verification, threshold re-authorization). Integration with eID wallets, SSI, and decentralized ledgers is ongoing (Hansen et al., 2024, Cui et al., 2024).

In summary, reusable authentication schemes are foundational to robust, high-assurance identity and authorization ecosystems, enabling secure, private, and scalable multi-session interaction while preserving usability and operational efficiency. Specific cryptographic choices dictate precise security properties, trade-offs, and applicability domains; technical advances continue to refine composability, privacy, and quantum-resistance.