Glossary of quantum terms

A symmetric block cipher approved by the U.S. government for protecting electronic data, using one key to both encrypt and decrypt. Because a symmetric cipher does not rest on the mathematics Shor’s algorithm attacks, AES is affected differently by quantum computing than public-key algorithms such as RSA.

Source: NIST , CNSSI 4009-2022, adapted from FIPS 197 (csrc.nist.gov)

An entity authorized to create, sign, issue and revoke public key certificates. NIST’s own term is certification authority, though certificate authority is common in practice.

Source: NIST , CNSSI 4009-2022 (csrc.nist.gov)

The result of a cryptographic transformation of data that, when properly implemented, provides a mechanism for verifying origin authentication, data integrity and signatory non-repudiation. Signatures prove where data came from rather than keeping it secret, which is why they are standardized separately from encryption as ML-DSA and SLH-DSA.

Source: NIST , NIST SP 800-175B Rev. 1 (csrc.nist.gov)

Public-key cryptography built on elliptic curves, which NIST specifies for U.S. government use in SP 800-186 under discrete-logarithm-based cryptography. The discrete logarithm is the second of the two problems a cryptographically relevant quantum computer would solve, so ECC is replaced in a post-quantum migration alongside RSA.

Source: NIST , NIST SP 800-186: Recommendations for Discrete Logarithm-Based Cryptography (csrc.nist.gov)

A function on bit strings in which the length of the output is fixed. Approved hash functions are designed so that it is computationally infeasible to find an input mapping to a given output, or two distinct inputs mapping to the same one. SLH-DSA builds its signatures on this property rather than on lattices.

Source: NIST , NIST SP 800-175B Rev. 1 (csrc.nist.gov)

A set of services providing interoperable, cryptographically based security for IPv4 and IPv6: access control, connectionless integrity, data origin authentication, rejection of replayed packets, and confidentiality through encryption. IPsec secures traffic below the application, so it protects systems that cannot be changed themselves.

Source: NIST , CNSSI 4009-2022 (csrc.nist.gov)

A procedure that results in secret keying material shared among different parties. It is the step a quantum computer threatens first, and the step ML-KEM replaces.

Source: NIST , NIST SP 800-56A Rev. 3 (csrc.nist.gov)

TLS in which both ends authenticate, not just the server. The server sends a CertificateRequest when certificate-based client authentication is wanted, and omits it when it is not; mTLS is the arrangement where it is always sent, so each side proves who it is.

Source: IETF , RFC 8446: TLS 1.3, section 4.3.2 (www.rfc-editor.org)

One of the elliptic curves NIST recommends for U.S. federal government use, specified in SP 800-186 as a pseudorandom Weierstrass curve over a 256-bit prime field. NIST puts its approximate security strength at 128 bits, the same table entry it gives Curve25519. Like every curve in that document it is a classical algorithm: a cryptographic inventory records it as work to be migrated, not as a post-quantum control.

Source: NIST , NIST SP 800-186, Section 3.2.1.3 (csrc.nist.gov)

A framework that is established to issue, maintain and revoke public key certificates. A PKI is what makes a certificate trustworthy, so an inventory of an organization’s cryptography is largely an inventory of what its PKI has issued.

Source: NIST , FIPS 186-5 (csrc.nist.gov)

A process that generates a random sequence of values, using one or more non-deterministic bit sources and a processing function that outputs an unpredictable, uniformly distributed sequence. Key strength depends on it: a predictable generator produces predictable keys whatever algorithm consumes them.

Source: NIST , CNSSI 4009-2022 (csrc.nist.gov)

A public-key algorithm used for key establishment and for generating and verifying digital signatures. Its security rests on the difficulty of factoring large numbers, which is one of the two problems a cryptographically relevant quantum computer would solve, so RSA is among the algorithms a post-quantum migration has to replace.

Source: NIST , NIST SP 800-175B Rev. 1 (csrc.nist.gov)

A security protocol providing privacy and data integrity between two communicating applications, composed of the TLS Record Protocol and the TLS Handshake Protocol. TLS carries most of the encrypted traffic on a typical network, so it is usually where a post-quantum migration starts.

Source: NIST , CNSSI 4009-2022 (csrc.nist.gov)

The scalar multiplication function RFC 7748 defines over Curve25519, used for elliptic-curve Diffie-Hellman key establishment with 32-byte keys at around the 128-bit security level. It is the classical half of X25519MLKEM768, and on its own it is one of the key exchanges a post-quantum migration is replacing, because a cryptographically relevant quantum computer solves the discrete logarithm problem its security rests on.

Source: IETF , RFC 7748: Elliptic Curves for Security (www.rfc-editor.org)

A quantum computer capable of breaking the public-key cryptography in use today. No such machine is known to exist, and QuSecure publishes no prediction of when one will; the reason to migrate before then is that encrypted data captured today can be stored until one exists.

Source: NIST , NIST CSWP 39-upd1 (csrc.nist.gov)

The capabilities needed to replace and adapt cryptographic algorithms in protocols, applications, software, hardware, firmware and infrastructures while preserving security and ongoing operations. It is the property that makes a migration a configuration change rather than a rebuild.

Source: NIST , NIST CSWP 39-upd1 (csrc.nist.gov)

A physical source of information whose output either appears random in itself or is made so by a filtering process, used as input to a random number generator. Where that physical process is a quantum one, the source is a QRNG.

Source: NIST , NIST SP 800-90B (csrc.nist.gov)

A set of three cryptographic algorithms (KeyGen, Encaps and Decaps) that two parties use to establish a shared secret key over a public channel. It is the shape most post-quantum encryption takes, which is why the standardized algorithm is named ML-KEM rather than being described as an encryption scheme.

Source: NIST , FIPS 203 (csrc.nist.gov)

NIST’s standardized post-quantum digital signature algorithm, published as FIPS 204. Signatures prove where data came from rather than keeping it secret, so ML-DSA is what replaces the signing side of a certificate chain.

Source: NIST , FIPS 204 (csrc.nist.gov)

NIST’s standardized post-quantum key-encapsulation mechanism, published as FIPS 203. It is the algorithm that replaces the key exchange in protocols like TLS, and its security rests on lattice problems rather than on the factoring and discrete-logarithm problems a quantum computer can solve.

Source: NIST , FIPS 203 (csrc.nist.gov)

Cryptography designed to secure electronic information against the future threat of quantum computers, which could eventually break many of today’s widely used cryptographic systems. PQC runs on ordinary hardware; NIST released the principal three standards in 2024 as ML-KEM, ML-DSA and SLH-DSA.

Source: NIST , NIST Post-Quantum Cryptography project (csrc.nist.gov)

A method for two parties to agree a shared key using the properties of quantum mechanics, carried over a dedicated optical link; ITU-T Y.3800 describes the networks that support it. QKD is not post-quantum cryptography, which is software running on ordinary hardware, and QuProtect uses the latter.

Source: ITU-T , ITU-T Y.3800: Overview on networks supporting quantum key distribution (www.itu.int)

An entropy source that draws its randomness from a quantum noise process rather than from an algorithm; ITU-T X.1702 standardizes the architecture. The distinction matters for keys: a deterministic generator derives its output from a secret seed, so anyone who obtains that seed can reproduce the sequence, while the result of a quantum measurement is not determined by any prior value.

Source: ITU-T , ITU-T X.1702 (11/2019) (www.itu.int)

QuSecure’s own protocol layer, built rather than adopting TLS so that the post-quantum algorithms perform well and so the layer does not depend on a third-party certification authority.

Source: QuSecure , Why not just the NIST algorithms?

NIST’s standardized hash-based post-quantum signature algorithm, published as FIPS 205. Its security rests on hash functions rather than on lattices, so it is the alternative to ML-DSA for anyone who wants a second signature scheme built on different mathematics.

Source: NIST , FIPS 205 (csrc.nist.gov)

The hybrid key agreement most post-quantum TLS connections negotiate today, registered by RFC 10024 as a named group for TLS 1.3. It pairs X25519 elliptic-curve Diffie-Hellman with ML-KEM-768 and derives the shared secret from both halves concatenated, so the negotiation holds unless an attacker breaks the classical and the post-quantum algorithm alike. The client’s share is 1216 bytes against the 32 that X25519 sends alone, which is where the handshake cost of going hybrid shows up.

Source: IETF , RFC 10024: Post-Quantum Traditional (PQ/T) Hybrid Key Agreement Mechanisms for TLS 1.3 (www.rfc-editor.org)

An interface between two systems that are not physically connected and where any logical connection is manual rather than automated. An air-gapped environment cannot reach a vendor’s cloud, so anything deployed into one has to work without calling home.

Source: NIST , NIST SP 800-53 Rev. 5 (csrc.nist.gov)

Software that sits on the network between cloud service customers and cloud service providers, enforcing enterprise security policy on traffic that leaves the corporate perimeter. It is one of the tools an enterprise already runs, and it inspects access to cloud services rather than the cryptography those connections negotiate.

Source: NIST , NIST SP 800-215 (csrc.nist.gov)

A structured inventory of the cryptographic assets in a system: the algorithms, keys and certificates in use, and how they relate to the software components that use them. CycloneDX, which publishes the format, calls it a Cryptography Bill of Materials.

Source: OWASP CycloneDX , CycloneDX v1.6 (cyclonedx.org)

The practice of identifying, prioritizing and reducing cryptographic risk across systems before vulnerabilities are exploited. It is the discipline a CBOM exists to serve: an inventory is the input, and the exposure it reveals is what gets worked down.

Source: QuSecure , What is cryptographic exposure management?

The bill of materials standard the CBOM format belongs to, maintained by the OWASP Foundation with Ecma International’s Technical Committee for Software and System Transparency (TC54) and published as the international standard ECMA-424. One specification covers several kinds of inventory, among them software (SBOM), cryptography (CBOM), hardware and SaaS, so a cryptographic inventory can be handed to an auditor in the same document format as the software inventory beside it.

Source: OWASP CycloneDX , ECMA-424 (cyclonedx.org)

A device-management safeguard that watches endpoints for malicious activity and responds to it. NIST lists it beside mobile device management as a control for the risks of mobile and remote computing; like a CASB, it looks at the endpoint rather than at the cryptography a connection negotiates.

Source: NIST , NIST SP 800-66r2 (csrc.nist.gov)

The network of devices containing the hardware, software, firmware and actuators that allow them to connect, interact and exchange data. IoT devices are often the hardest part of an estate to migrate, because many cannot be updated in place.

Source: NIST , NIST SP 800-172r3 (csrc.nist.gov)

A fingerprint of a TLS client, taken from the ClientHello message it opens a connection with. JA3 reads five fields (the SSL version, the accepted ciphers, the extension list, the elliptic curves and the elliptic-curve point formats), concatenates their decimal values and MD5 hashes the result into a 32-character string that can be shared as threat intelligence. Because the negotiation is sent in the clear, the fingerprint can be taken passively, which is what makes it useful for seeing which clients and libraries are actually talking on a network. Salesforce published it in 2017; JA4 is its successor.

Source: Salesforce , Open Sourcing JA3, 2017 (engineering.salesforce.com)

FoxIO’s successor to JA3, reading the same TLS ClientHello but writing the result in three underscore-separated parts: a readable summary (the transport, the TLS version, whether SNI is present, how many ciphers and extensions were offered, and the first and last characters of ALPN), then a truncated hash of the cipher suites, then a truncated hash of the extensions and signature algorithms. The lists are sorted before they are hashed, so a client that varies its cipher or extension order no longer produces a different fingerprint on every connection, and the readable first part stays comparable by eye.

Source: FoxIO , JA4+ Network Fingerprinting, 2023 (blog.foxio.io)

QuSecure’s post-quantum cryptography platform. The R3 is its three capabilities: Recon discovers the cryptography an organization is running, Resilience changes it at the network layer by policy, and Reporting proves what changed with a CBOM.

Source: QuSecure , The QuProtect R3 platform

A formal record containing the details and supply chain relationships of the various components used in building software. An SBOM answers what software you are running; a CBOM answers what cryptography it uses.

Source: NIST , NIST SP 800-161r1-upd1 (csrc.nist.gov)

A computerized system that gathers and processes data and applies operational controls over long distances, typically across power transmission and distribution or pipeline systems. SCADA equipment is often long-lived and cannot be modified, which is what makes cryptography it depends on hard to change.

Source: NIST , NIST SP 800-82r3 (csrc.nist.gov)

A program that provides centralized logging capabilities for a variety of log types. A SIEM is usually where a security team already looks, which is why cryptographic findings are worth sending to one rather than to a separate console.

Source: NIST , NIST SP 800-92 (csrc.nist.gov)

Tooling that continuously monitors log events for known malicious and suspicious activity and generates reports on what it finds, alongside a SIEM. NIST names both as the tools behind a proactive approach to incident detection and response.

Source: NIST , NIST SP 800-61r3 (csrc.nist.gov)

A specific set of cryptographic algorithms and key strengths that may be used to protect classified and unclassified national security systems. The suite was announced in 2015, replacing the former release of Suite B algorithms; CNSA 2.0 is the current revision.

Source: NIST , CNSSI 4009-2022 (csrc.nist.gov)

The set of hardware, software or firmware that implements approved cryptographic functions, including key generation, within the module’s cryptographic boundary. The module, rather than the product around it, is the unit FIPS 140-3 describes.

Source: NIST , FIPS 140-3 (csrc.nist.gov)

The European regulation on digital operational resilience for the financial sector, in force since 2022. It consolidates ICT risk requirements that were previously spread across several financial services laws into one framework covering risk management, incident reporting, resilience testing and third-party providers.

Source: EUR-Lex , Regulation (EU) 2022/2554 (eur-lex.europa.eu)

A legally binding order given by the President, as head of the Executive Branch, to federal administrative agencies. Executive Orders generally direct agencies and officials in how they carry out laws or policies Congress has established, which is why federal cryptography deadlines usually arrive as one.

Source: NIST , CNSSI 4009-2022 (csrc.nist.gov)

Securing the Nation Against Advanced Cryptographic Attacks, the Executive Order directing federal agencies to move to post-quantum cryptography. It requires agencies to transition all high value assets and high impact systems to PQC for key establishment by 31 December 2030, and for digital signatures by 31 December 2031, excluding national security systems.

Source: Federal Register , Executive Order 14412, signed 22 June 2026 (www.federalregister.gov)

A standard for adoption and use by federal departments and agencies, developed within NIST’s Information Technology Laboratory. A FIPS covers a specific topic in information technology to achieve a common level of quality or some level of interoperability. The post-quantum algorithms are published as FIPS 203, 204 and 205.

Source: NIST , NIST SP 1800-12b (csrc.nist.gov)

The European regulation on the protection of natural persons with regard to the processing of personal data and on the free movement of such data. It treats the protection of personal data as a fundamental right, and the cryptography protecting that data in transit is part of how an organization meets it.

Source: EUR-Lex , Regulation (EU) 2016/679 (eur-lex.europa.eu)

The federal statute placing “an affirmative and continuing obligation” on each financial institution to respect its customers’ privacy and to protect the security and confidentiality of their nonpublic personal information. The safeguards its regulators require are where cryptography in transit and at rest comes in.

Source: U.S. Code , 15 U.S.C. 6801 (www.govinfo.gov)

A federal statute that called on the Department of Health and Human Services to establish regulatory standards protecting the privacy and security of individually identifiable health information.

Source: NIST , NIST SP 800-66r2 (csrc.nist.gov)

All categories of technology used for gathering, storing, transmitting, retrieving or processing information: microelectronics, computing systems, software, mobile telephony, satellite communications and networks. DORA frames its requirements as ICT risk, which is why the term appears in European financial regulation rather than only in engineering.

Source: NIST , NIST SP 800-161r1 (csrc.nist.gov)

The OMB memorandum that implements Executive Order 14412, issued two days after it. Agencies have 120 days from the memorandum to produce a migration plan, and it sets out the migration as five phases: strategy, planning and discovery through 2027, pilots and early migration, prioritized migration, signature migration in 2031, and full migration by 2035. It also discharges OMB’s duty under the Quantum Computing Cybersecurity Preparedness Act to tell agencies how to prioritize systems for migration, and it says automation is what makes a cryptographic inventory usable at federal scale. It does not apply to national security systems.

Source: The White House , OMB Memorandum M-26-15, 24 June 2026 (www.whitehouse.gov)

The European directive on measures for a high common level of cybersecurity across the Union, replacing the 2016 NIS Directive. It sets baseline cybersecurity risk-management and incident-reporting obligations across sectors including energy, transport, water and digital infrastructure.

Source: EUR-Lex , Directive (EU) 2022/2555 (eur-lex.europa.eu)

The U.S. Department of Commerce laboratory that issues the federal government’s cryptographic standards. Founded in 1901, its stated mission is to promote U.S. innovation and industrial competitiveness by advancing measurement science, standards and technology. In cryptography that means the FIPS series, which carries the post-quantum standards ML-KEM, ML-DSA and SLH-DSA, and the SP 800 series of recommendations that federal mandates point agencies at. NIST sets the algorithms; a mandate such as M-26-15 sets the date by which they have to be in use.

Source: NIST , About NIST (www.nist.gov)

NIST’s report describing its expected approach to moving from quantum-vulnerable algorithms to post-quantum signatures and key-establishment schemes. It names the existing standards that are quantum-vulnerable and the quantum-resistant ones products will need to transition to, which is what makes it the document a migration plan is written against.

Source: NIST , NIST IR 8547: Transition to Post-Quantum Cryptography Standards (csrc.nist.gov)

NIST’s recommendation for stateful hash-based signatures, specifying the Leighton-Micali Signature system and the eXtended Merkle Signature Scheme along with their multi-tree variants. Stateful schemes suit firmware and code signing, where a signer can track state; SLH-DSA is the stateless alternative for general use.

Source: NIST , NIST SP 800-208: Recommendation for Stateful Hash-Based Signature Schemes (csrc.nist.gov)

The 2022 policy directive setting United States government policy on migrating to quantum-resistant cryptography. It is the mandate that predates EO 14412 and is usually cited alongside CNSSP 15 for national security systems.

Source: The White House , National Security Memorandum on Promoting United States Leadership in Quantum Computing While Mitigating Risks to Vulnerable Cryptographic Systems, 4 May 2022 (bidenwhitehouse.archives.gov)

The New York Department of Financial Services regulation establishing cybersecurity requirements for financial services companies. It applies to Covered Entities licensed in New York, which is why it reaches institutions headquartered elsewhere.

Source: NYDFS , 23 NYCRR Part 500 (www.dfs.ny.gov)

The payment security standard intended for entities that store, process or transmit payment account data, and for developers and manufacturers of the software and devices used in those transactions.

Source: PCI Security Standards Council , PCI Security Standards Council (www.pcisecuritystandards.org)

An examination of the controls at a service organization relevant to security, availability, processing integrity, confidentiality or privacy. A SOC 2 report is what a customer asks a vendor for as evidence, which is why the ability to export cryptographic evidence on demand matters to one.

Source: AICPA , SOC 2: Reporting on an Examination of Controls at a Service Organization (www.aicpa-cima.com)

A collection of concepts and ideas designed to minimize uncertainty in enforcing accurate, least-privilege per-request access decisions in information systems and services in the face of a network viewed as compromised. Knowing which cryptography protects a given request is a prerequisite for making that decision about it.

Source: NIST , NIST SP 800-207 (csrc.nist.gov)

The National Coordinator for Critical Infrastructure Security and Resilience, which leads the national effort to understand, manage and reduce risk to cyber and physical infrastructure. EO 14412 directs CISA to issue the guidance agencies follow when migrating their systems.

Source: CISA , About CISA (www.cisa.gov)

A governmentwide program providing a standardized approach to security assessment and authorization for cloud products and services used by U.S. federal agencies. An agency buying a cloud service generally expects it to hold a FedRAMP authorization at a baseline matching the sensitivity of the data involved.

Source: FedRAMP , FedRAMP program overview (www.fedramp.gov)

The GSA program, also called schedules or the Federal Supply Schedule, through which federal, state, local and tribal governments and other eligible buyers get commercial products and services at pre-negotiated prices. It is one of the routes an agency uses to buy without running its own competition.

Source: GSA , GSA Multiple Award Schedule program (www.gsa.gov)

Federal information or a federal information system designated as a high value asset under OMB Memorandum M-19-03 or any successor document. HVAs are the systems EO 14412 puts first in the migration, alongside high impact systems.

Source: Federal Register , Executive Order 14412, section 4(d) (www.federalregister.gov)

Temporary authorization to test an information system in a specified operational environment, within the timeframe and under the conditions set out in the written authorization. An IATT permits testing on a live network; it is not an authorization to operate there.

Source: NIST , CNSSI 4009-2022 (csrc.nist.gov)

The level of the DoD Cloud Computing Security Requirements Guide that covers non-controlled unclassified information: everything cleared for public release, plus low-confidentiality information not designated CUI. It is the entry point rather than a separate assessment, since the DoD grants an IL2 provisional authorization with full reciprocity to a cloud service holding a FedRAMP Moderate or High authorization. IL6 is the same guide’s level for information classified up to SECRET.

Source: Microsoft , DoD Impact Level 2, citing Cloud Computing SRG sections 5.1.1 and 5.2.2.1 (learn.microsoft.com)

The level of the DoD Cloud Computing Security Requirements Guide reserved for information classified up to SECRET. The SRG is maintained by DISA and defines the baseline a cloud service is assessed against; an IL6 provisional authorization builds on a FedRAMP High authorization supplemented with DoD-specific controls, and the infrastructure must be dedicated and operated under contract to the DoD or a federal agency.

Source: Microsoft , DoD Impact Level 6, citing Cloud Computing SRG sections 5.1.1 and 5.2.2.4 (learn.microsoft.com)

A system whose function involves intelligence activities, cryptologic activities related to national security, command and control of military forces, or equipment integral to a weapons system, or which is protected at all times by procedures for classified information. National security systems are governed separately from ordinary federal systems, which is why CNSA applies to them rather than the civilian baselines.

Source: NIST , CNSSI 4009-2022 (csrc.nist.gov)

The office that serves the President in overseeing implementation across the Executive Branch, assisting with policy, budget, management and regulatory objectives. Federal cryptography deadlines usually reach agencies as an OMB memorandum telling them how to carry out an Executive Order.

Source: The White House , Office of Management and Budget (www.whitehouse.gov)

A national group and cooperative purchasing organization, built so that smaller agencies, schools and businesses can buy at prices their own volume would not earn them. It is one of the cooperative vehicles a state or local buyer uses instead of running a competition.

Source: OMNIA Partners , About OMNIA Partners (www.omniapartners.com)

A federal program awarding non-dilutive, equity-free funding to American small businesses to develop technology and chart a path toward commercialization.

Source: SBIR , America's Seed Fund program overview (www.sbir.gov)

A NASA-run Government-Wide Acquisition Contract providing information technology, communications and audio-visual products and services to all federal agencies and their approved contractors. It is one of the vehicles an agency uses to buy software without running its own competition.

Source: NASA SEWP , NASA SEWP program overview (www.sewp.nasa.gov)