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Post-quantum migration creates an architectural impasse for distributed signatures

Replacing legacy cryptography across distributed networks forces custodians to choose between native verification, resistance to lone signers, and long-term protocol agility.

By Primary News Team

17 statements added · 9 Oct see what was added
Post-quantum migration creates an architectural impasse for distributed signatures
Source: US Department of Energy
Published9 Oct 2026, 18:49 Last updated9 Oct 2026, 18:49 Sources
Source mode Marks each sentence drawn from a source or a contributor

When a single computer signs a digital transaction, upgrading to quantum-resistant mathematics is a straightforward software replacement. The machine produces a fresh key pair under an algorithm designed to withstand future quantum computers, publishes the public verification key, and calculates signatures using the updated mathematical formulas. The downstream recipient runs an updated verification function against the new public key. While the underlying algebraic operations change, the fundamental architecture of the system remains untouched: one private key produces one cryptographic signature for one recipient to inspect.

That operational simplicity breaks down when authority over an action is intentionally divided among several independent servers, institutions, or corporate custodians. In high-value financial networks and critical infrastructure, allowing a lone machine to hold an entire private key introduces a catastrophic point of failure. Organizations instead distribute custody across several participants, storing mathematical fragments of the secret key across distinct servers so that no lone node ever holds the complete private key. Authorizing an action requires a designated threshold of these independent parties to compute together over a network.

Upgrading these distributed networks to post-quantum standards exposes an unresolved systems conflict. In single-signer cryptography, replacing an algorithm merely requires changing the code behind an application programming interface.12 In distributed custody, changing the signature algorithm fundamentally reorganizes how secret shares are distributed, how participants interact during signing, and how compromised keys are refreshed.2 A new analysis posted to the arXiv preprint server shows that distributed authorization systems face an unavoidable structural trade-off when moving to post-quantum standards.13

Why does dividing a post-quantum key create systems problems?

Dividing a signature algorithm across multiple participants requires the underlying mathematics of the scheme to support cooperative calculation without revealing secret fragments. To see why post-quantum algorithms disrupt this process, consider the chain of events that must take place during any threshold transaction. First, a set of participants must execute a distributed key generation ceremony to compute a shared public key and private mathematical shares without any participant seeing the complete private key. Second, when an action requires approval, a minimum quorum of participants must run an interactive protocol, generating partial calculations and exchanging messages over a network. Third, these partial calculations are combined into a final cryptographic artifact.12 Finally, a downstream verifier checks whether the artifact satisfies the required authorization rules.

In classical elliptic-curve cryptography, such as ECDSA or Schnorr signatures, the linear algebraic structure of the signing equations allows participants to add their secret shares together smoothly during an interactive signing session.12 Because the mathematics relies on linear equations, servers can manipulate their individual secret shares locally and combine their intermediate outputs through straightforward multiplication and addition over an elliptic curve. The resulting artifact is an ordinary, single signature indistinguishable from one produced by a lone computer. The receiving system verifies the signature with standard code, unaware that several servers collaborated across distinct data centers to produce it.

Post-quantum algorithms discard this convenient linear structure. The primary post-quantum signature standards established by the United States National Institute of Standards and Technology, including the lattice-based algorithm ML-DSA and the hash-based algorithm SLH-DSA, were standardized exclusively for conventional single-signer operations.12 Because lattice and hash-based signing equations involve non-linear steps, complex sampling from discrete Gaussian distributions, and selective abort steps to prevent information leakage, constructing cooperative threshold versions is far more intricate.12 Standardized hash-based signatures, for instance, cannot be evaluated in a black-box threshold manner without distributed hash trees, specialized precomputations, or additional state coordination.12

Dariia, the paper's author and a researcher at EternaX Labs, explained the friction that emerges when attempting to distribute these algorithms across independent nodes. Speaking in response to questions from Primary, Dariia said that "ML-DSA use rejection steps, while SLH-DSA main obstacle is a large number of non-linear hash and pseudorandom function evaluations."contributed Dariia added that in ML-DSA, "parties must jointly generate randomness, compute a challenge and response, check bounds, and sometimes restart without letting an abort leak information about any share."contributed For hash-based schemes, Dariia noted that "a function applied to a shared seed cannot generally be evaluated by applying it separately to each share and combining the results; the parties must instead evaluate the hash-based signing relation cooperatively."contributed Classical schemes, by contrast, "benefit from algebraic structure that makes many shared operations substantially more direct."contributed

Commenting on this friction, Mina offered another perspective on the severity of the obstacle. Speaking to Primary, Mina said that while lattice-based schemes introduce rejection sampling and non-linearities, "the obstacle is significant, but I would describe it as an engineering and efficiency challenge rather than a fundamental impossibility."contributed Mina pointed out that researchers have demonstrated threshold schemes compatible with standardized lattice-based algorithms like ML-DSA, arguing that "the gap today is primarily one of performance, complexity, and operational maturity rather than feasibility."contributed

Post-quantum migration creates an architectural impasse for distributed signatures
Source: X

How does the architectural boundary classify authorization systems?

The architectural boundary classifies distributed signing designs across three core operational properties: native-signature compatibility, unilateral-signing resistance, and threshold-layer agility.12 In a research paper posted in September 2026, Dariia Porechna of EternaX Labs mapped these engineering tensions across five major distributed authorization families.3 The framework defines native-signature compatibility as the ability to produce a single signature that satisfies an unmodified conventional verifier without extra proofs or altered rules.1 Unilateral-signing resistance requires that no single participant, dealer, or hardware module ever possesses or reconstructs material sufficient to sign alone.1 Threshold-layer agility measures whether the signature algorithm can be replaced without overhauling the threshold protocol, share storage, and internal quorum state.12

Porechna evaluated specialized threshold signatures, generic secure multiparty computation, distributed hash-based schemes, programmable multisignatures, and threshold-authorized hardware security modules.1 Across all surveyed families, no single architecture simultaneously achieves native output, resistance to unilateral signing, and threshold-layer agility.2 Porechna notes that this represents an architectural tension rather than a formal mathematical impossibility proof.12 System designers can preserve any two characteristics, but achieving the third requires giving up one of the others.

When asked whether specific hybrid network topologies or restricted committee sizes could dissolve this tension, Dariia told Primary that "the boundary is logical rather than a matter of network topology or committee size."contributed Dariia noted that if a destination verifier demands a single native signature and no single device may hold the complete private key, the native mathematical relation must be executed across a distributed network or within a cryptographic circuit, cementing the signature scheme into the threshold infrastructure. Dariia added that "all three can appear to coexist only if one weakens a definition," such as "by calling a programmable quorum 'native', treating a complete-key HSM as distributed custody, or counting an MPC engine as agile."contributed

Evaluating this finding, Mina told Primary that "the trilemma captures a real and important challenge in current distributed-signing architectures."contributed Mina noted that threshold protocols remain tightly coupled to key management and signing logic, adding that "many of today's designs appear unable to simultaneously provide native-signature compatibility, threshold agility, and unilateral-signing resistance without significant trade-offs."contributed

Specialized native threshold signatures, including threshold lattice constructions and classical schemes such as FROST or threshold ECDSA, preserve native verification and prevent any participant from holding the complete key.12 Commercial custody platforms, including Fireblocks through its MPC-CMP implementation and BitGo through threshold wallets, deploy specialized protocols so that transactions appear on blockchains as conventional single-key operations.12 However, these systems exhibit no threshold-layer agility. Moving from ECDSA to a post-quantum lattice signature requires overhauling the distributed key generation ceremonies, the interactive signing protocols, the state refresh routines, and the underlying mathematical security arguments.1

Asked which protocol subsystem imposes the heaviest migration burden during an upgrade to lattice cryptography, Dariia noted that the paper provides a taxonomy rather than an empirical benchmark, meaning there is no universal cost ranking. Dariia stated that distributed key generation and persistent share storage have the broadest architectural impact because a new algorithm fundamentally alters the structure of the key, forcing organizations to execute fresh sharing ceremonies, update backup routines, and rewrite share-refresh protocols. At the same time, Dariia observed that the interactive signing protocol often represents the most difficult cryptographic engineering hurdle because distributed lattice sampling and abort mechanisms differ entirely from classical arithmetic.

Mina concurred that the cryptographic core requires reconstruction, telling Primary that organizations can preserve governance, auditing, and orchestration layers while the signing protocols themselves undergo a major redesign. Mina explained: "I would therefore describe the migration as an adaptation of the broader infrastructure coupled with a major rebuild of the cryptographic layer, rather than a complete restart from scratch."contributed

Generic multiparty computation avoids protocol redesigns by evaluating the signature algorithm as an abstract arithmetic circuit over secret-shared data. While this approach keeps the underlying multiparty computation software stable, Porechna reports that it fails the definition of threshold-layer agility because the signing circuit, native key shares, validation routines, and failure-handling procedures must still be rewritten for each new algorithm family.12 Furthermore, evaluating complex post-quantum hash or lattice operations inside general secure computation circuits introduces immense computational and communication overhead.1

When asked what theoretical breakthrough could overcome this trade-off, Dariia explained that generic multiparty computation already proves the combination is possible in theory, because general secure computation can evaluate any efficiently computable function without exposing secret keys. Dariia said that "the obstacle is practicality and deployability," noting that post-quantum evaluations require massive distributed computation and network communication for sampling loops, hash rounds, and consistency checks.contributed Dariia told Primary that while generic circuits demonstrate theoretical feasibility, today they remain "operationally and economically irrational compared with purpose-built protocols or programmable authorization."contributed Dariia added that the clearest computational bottleneck in hash-based signing is evaluating standardized hash functions over secret shares, because those non-linear functions cannot be broken into separate local evaluations across participating nodes.

Post-quantum migration creates an architectural impasse for distributed signatures
Source: Zodia Custody

What trade-offs emerge when moving authorization outside the native signature?

Moving authorization logic outside the native mathematical signing equation decouples the threshold protocol from the underlying algorithm but surrenders either native compatibility or trust distribution. Programmable systems, such as smart contract multisignatures and dual-gate architectures, achieve high threshold-layer agility and maintain resistance to unilateral compromise.2 In these systems, each participant signs an approval using their own independent post-quantum key pair, and an on-chain contract or smart rule verifies the individual signatures to confirm that the required threshold was met.12 Each participant can upgrade their personal algorithm from ECDSA to ML-DSA independently without altering the shared coordination logic.

The cost of programmable multisignature systems is the complete loss of native-signature compatibility. The output is a list of distinct signatures and contract execution data rather than a single signature accepted by standard legacy accounts. In environments with fixed verifiers, such as the Bitcoin base layer or legacy enterprise authentication endpoints where a single ECDSA or Schnorr signature is strictly mandated, programmable authorization data cannot be processed directly.12

To bridge this gap for legacy systems, enterprise custody architectures often deploy threshold-authorized hardware security modules. Custody provider Zodia Custody, for example, documents infrastructure supporting hardware security module custody alongside multiparty computation services.12 In a threshold-authorized hardware module design, participants run a flexible, algorithm-agnostic threshold layer to approve a transaction.12 Once the threshold is verified, a physical hardware module holding the complete private key creates a native signature. While this preserves both native output and agility across the threshold committee, it introduces a centralized trust boundary. An adversary or insider who breaches the hardware module can sign unilaterally, violating the fundamental guarantee of distributed threshold custody.1

Discussing the vulnerabilities of this model, Dariia cited practical hardware failure modes that fall outside idealized protocol guarantees. Dariia told Primary that "a compromised HSM firmware or an API-level authorization bypass" allows an attacker to "invoke a complete private key without the external quorum."contributed In genuine multi-party protocols where keys are truly divided, Dariia pointed out that physical attacks focus on different vectors, such as side-channel leakage through power consumption, memory timing, or fault injection that could reveal an individual participant's share over repeated signing sessions. Dariia emphasized that the taxonomy categorizes where trust and algorithm dependencies reside, but does not evaluate physical side-channel defenses.

What are the limits of the framework?

The conclusions in the research paper reflect a structural taxonomy of public cryptographic mechanisms through August 2026 rather than an empirical benchmark of computational speeds or network bandwidth. The analysis assumes that all deployed software components, hardware modules, and cryptographic libraries execute their configured protocols faithfully according to their specifications.2 It does not measure the performance overhead, latency degradation, or bandwidth costs that occur when specific post-quantum algorithms run across real-world networks.

The paper also does not address operational failure modes such as administrative overrides, emergency key recovery protocols, implementation flaws, or system availability during network partitions. The findings describe how the architectural placement of the signing relation restricts migration agility under formal definitions, but they cannot predict how future algorithmic discoveries might alter specific protocol efficiencies. The paper was posted as a preprint and has not undergone formal journal peer review.12

What comes next for post-quantum distributed authorization?

As regulatory bodies and federal policies enforce firm deadlines for migrating sensitive data and financial infrastructure to post-quantum standards, custody operators must choose which architectural trade-offs to accept.12 Custodians protecting fixed, non-programmable ledgers must invest in complex, scheme-specific post-quantum threshold protocols, accepting that future algorithm upgrades will require coordinated replacements of their internal key-share state and ceremony infrastructure.

Mina observed that when forced to choose during this transition period, institutions are unlikely to compromise on distributed trust. Speaking to Primary, Mina said: "I expect institutional custody providers to prioritize distributed trust and cryptographic agility over strict native signature compatibility."contributed Mina added that eliminating single points of failure remains the primary value of multiparty computation, meaning that "native-signature compatibility is the compromise institutions are most likely to accept first, while continuing to preserve the security and governance benefits that made threshold custody attractive in the first place."

Consequently, operators building on modern programmable platforms are likely to bypass native threshold signing altogether, relying on modular multi-key verification where individual participant keys can migrate independently. For institutions operating across both environments, hybrid authorization bridges and dual-gate verification will become mandatory operational layers during the decades-long transition to quantum-safe cryptography.

What this rests on

45 sentences trace to 3 sources and 2 contributors.

  1. 1 DP Dariia Porechna Paper · arxiv.org · 4 Sep 2026 The Native-Signature Boundary in Post-Quantum Distributed Authorization Preprint · may not have been peer reviewed See the source
  2. 2 A arxiv.org Paper · arxiv.org The Native-Signature Boundary inPost-Quantum Distributed Authorization Preprint · may not have been peer reviewed See the source
  3. 3 A arxiv.org Paper · arxiv.org Cryptography and Security Preprint · may not have been peer reviewed See the source
  4. 4 D Dariia Contributor · interview 9 Sep 2026 · in the article since 9 Oct 2026 Contribution — Dariia 11 statements added to this article
  5. 5 M Mina Contributor · interview 24 Sep 2026 · in the article since 9 Oct 2026 Contribution — Mina 6 statements added to this article

Article history

  1. Published 9 Oct 2026, 18:49
    Assembled by the Primary desk from 3 sources · 2 contributors · 45 cited sentences
  2. Mina 6 statements added 16 days before publication
    1. Go to the sentence: Speaking to Primary, Mina said that while lattice-based schemes introduce rejection sampling and non-linearities, "the obstacle is significant, but I would describe it as an engineering and efficiency challenge rather than a fundamental impossibility."
    2. Go to the sentence: Mina pointed out that researchers have demonstrated threshold schemes compatible with standardized lattice-based algorithms like ML-DSA, arguing that "the gap today is primarily one of performance, complexity, and operational maturity rather than feasibility."
    3. Go to the sentence: Evaluating this finding, Mina told Primary that "the trilemma captures a real and important challenge in current distributed-signing architectures."
    4. Go to the sentence: Mina noted that threshold protocols remain tightly coupled to key management and signing logic, adding that "many of today's designs appear unable to simultaneously provide native-signature compatibility, threshold agility, and unilateral-signing resistance without significant trade-offs."
    5. Go to the sentence: Mina explained: "I would therefore describe the migration as an adaptation of the broader infrastructure coupled with a major rebuild of the cryptographic layer, rather than a complete restart from scratch."
    6. Go to the sentence: Speaking to Primary, Mina said: "I expect institutional custody providers to prioritize distributed trust and cryptographic agility over strict native signature compatibility."
  3. Dariia, the paper's author and a researcher at EternaX Labs 11 statements added 31 days before publication
    1. Go to the sentence: Speaking in response to questions from Primary, Dariia said that "ML-DSA use rejection steps, while SLH-DSA main obstacle is a large number of non-linear hash and pseudorandom function evaluations."
    2. Go to the sentence: Dariia added that in ML-DSA, "parties must jointly generate randomness, compute a challenge and response, check bounds, and sometimes restart without letting an abort leak information about any share."
    3. Go to the sentence: For hash-based schemes, Dariia noted that "a function applied to a shared seed cannot generally be evaluated by applying it separately to each share and combining the results; the parties must instead evaluate the hash-based signing relation cooperatively."
    4. Go to the sentence: Classical schemes, by contrast, "benefit from algebraic structure that makes many shared operations substantially more direct."
    5. Go to the sentence: When asked whether specific hybrid network topologies or restricted committee sizes could dissolve this tension, Dariia told Primary that "the boundary is logical rather than a matter of network topology or committee size."
    6. Go to the sentence: Dariia added that "all three can appear to coexist only if one weakens a definition," such as "by calling a programmable quorum 'native', treating a complete-key HSM as distributed custody, or counting an MPC engine as agile."
    7. Go to the sentence: Moving from ECDSA to a post-quantum lattice signature requires overhauling the distributed key generation ceremonies, the interactive signing protocols, the state refresh routines, and the underlying mathematical security arguments.
    8. Go to the sentence: Furthermore, evaluating complex post-quantum hash or lattice operations inside general secure computation circuits introduces immense computational and communication overhead.
    9. Go to the sentence: Dariia said that "the obstacle is practicality and deployability," noting that post-quantum evaluations require massive distributed computation and network communication for sampling loops, hash rounds, and consistency checks.
    10. Go to the sentence: Dariia told Primary that while generic circuits demonstrate theoretical feasibility, today they remain "operationally and economically irrational compared with purpose-built protocols or programmable authorization."
    11. Go to the sentence: Dariia told Primary that "a compromised HSM firmware or an API-level authorization bypass" allows an attacker to "invoke a complete private key without the external quorum."