Research · Foundations
A small cryptography glossary
The terms used throughout these docs, with the distinctions that matter when reading a security claim.
Keys and protocols
- AEAD
- Authenticated encryption with associated data: hides plaintext and checks integrity while authenticating additional unencrypted context.
- Associated data
- Context checked by AEAD but not encrypted, such as a version or header field. Authentication does not make it secret.
- KEM
- A key-encapsulation mechanism: encapsulation creates a ciphertext and shared secret; the corresponding private key recovers that secret by decapsulation.
- Hybrid cryptography
- A construction combining components, often classical and post-quantum. Its security depends on the combiner, authentication, inputs and attack model.
- HKDF
- A key-derivation construction with extraction and expansion stages. Domain-specific context helps keep derived keys in separate roles.
- Nonce
- A value used with encryption that must meet the chosen algorithm’s uniqueness or randomness requirements. It is not ordinarily secret.
- Salt
- A public input used to vary a derivation. A fresh random salt gives probabilistic separation; it is not a new secret.
- Ratchet
- A state machine that evolves key material as communication progresses. Symmetric, DH and post-quantum mechanisms can have different update and recovery events.
- Skipped key
- A retained message key for a not-yet-received position. It permits out-of-order delivery while extending exposure if retained state is stolen.
- Transcript
- The protocol’s encoded or modeled record of messages and context. Exactly which fields it binds is security-relevant.
Continue with cryptographic foundations and Auris’s exact formats.
Properties and evidence
- Authentication
- Evidence of a key holder or authorized protocol participant under stated assumptions. A link from a key to a human requires its own trust basis.
- Deniability
- A property defined against a particular judge or transcript test; it is not simply encryption or absence of server logs.
- Forward secrecy
- Protection of past secrets against specified later compromises, with retained keys and erasure assumptions made explicit.
- Post-compromise security
- Recovery of future secrecy after a specified compromise ends and fresh secret material is successfully incorporated.
- Pre-use
- A test boundary before information derived from the tested key is exposed. A pre-use theorem need not cover an operational channel.
- Symbolic model
- A formal system treating cryptographic operations as abstract terms and equations. The permitted attacker and transitions define its scope.
- Reachability witness
- A valid execution showing that a modeled situation can occur. It helps expose vacuous properties and is not an exhaustive search result.
- Conformance
- Evidence that concrete bytes or implementation transitions satisfy a specified contract. Selected vectors are a limited form.
- Metadata
- Information around content: addresses, timing, sizes, routing identifiers, relationships and activity.
- Quorum
- An accepted set of participants or signatures. Intersection alone does not establish an honest intersection when some participants are corrupt.
- Confidence interval
- A procedure’s uncertainty statement under a statistical model. Its interpretation depends on sampling assumptions and the population measured.
- Counterexample
- A valid case contradicting a stated universal claim. It refutes that statement’s scope, not automatically every related design.
See evidence levels, authentication and witnesses and measurement.
Reviewed · Review scope and versions