Plain-English glossary

Short definitions for terms used across the project. Product and compliance claims are governed by the linked technical documents, not by these simplified descriptions.

Privacy and streaming

Term	Plain-English meaning
AI gateway / LLM gateway	Software placed between an application and a model provider to inspect, change, route, or record requests and responses.
Proxy / reverse proxy	A service that receives a client's request and sends it to another service on the client's behalf.
Upstream	The model service or gateway to which this proxy sends a transformed request.
Configured upstream boundary	The exact request bytes handed to the configured upstream network client after the proxy finishes its transformations.
In-VPC	Running inside the operator-controlled virtual private cloud or equivalent private network.
Zero egress	In this project, declared unredacted protected values are absent at the configured upstream boundary. It does not mean the process makes no network request.
PII	Personally identifiable information, such as an email address or government identifier.
PHI / ePHI	Health information protected by HIPAA; ePHI is the electronic form.
PCI data	Payment-card information governed by PCI DSS controls.
Redaction	Removing or replacing a protected value before forwarding content.
Masking / tokenization	Replacing a protected value with a safer representation or placeholder.
Placeholder	A temporary marker such as [EMAIL_1] that stands in for a protected value.
Rehydration	Replacing an authorized placeholder with its original value on the response path.
SSE	Server-Sent Events, an HTTP format that delivers model output incrementally as data: events.
Fragmentation	A logical value being split across multiple network, byte, or SSE chunks.
Sliding-window buffer	A small retained suffix used to decide whether the end of one chunk could be the start of a placeholder completed by a later chunk.
Bounded state	Memory retained by an algorithm has a declared upper bound instead of growing with the full stream.

Detection and transformation

Term	Plain-English meaning
Detection tier	One stage of the local detector pipeline, such as structured patterns, entropy, or an optional entity model.
Shannon entropy	A measure of character unpredictability used here as a heuristic for secret-like strings. High entropy is not proof that a string is a secret.
NER	Named-entity recognition, a model that labels text spans such as people, organizations, or places.
ONNX	A portable model format and runtime used for the optional local NER tier.
Regex	A pattern used to find structured text such as an email or SSN.
DFA	Deterministic finite automaton, a pattern-matching method that can avoid catastrophic regex backtracking for supported patterns.
ReDoS	Regular-expression denial of service, where a pathological pattern or input consumes excessive CPU.
AST	Abstract syntax tree, a parsed representation of structured data that lets the proxy change values without editing raw JSON text blindly.
JSON-RPC	A JSON-based request and response protocol commonly used by tools and MCP servers.
MCP	Model Context Protocol, a protocol through which models or agents discover and call tools.
Tool call	A structured model request to execute a named function or external capability.

Access and network security

Term	Plain-English meaning
RBAC	Role-based access control: permissions are assigned to roles, and identities receive roles.
Policy as code	Access and security rules stored in machine-readable configuration and evaluated by software.
OPA	Open Policy Agent, an external engine that evaluates policy rules.
Fail closed	Deny or stop when a security decision cannot be completed safely.
SSRF	Server-side request forgery, where an attacker tricks a server into reaching an unintended network address.
DNS rebinding	Changing a hostname's resolved address to bypass an earlier network check.
mTLS	Mutual TLS, where both ends of a connection authenticate with certificates.
UDS	Unix domain socket, a local operating-system communication channel that does not use a TCP network port.
ASGI	The Python interface between asynchronous web servers and applications such as FastAPI.

Cryptography and audit evidence

Term	Plain-English meaning
AES-256-GCM	Authenticated encryption that hides data and detects ciphertext modification.
DEK	Data-encryption key used to encrypt a particular value or data set.
HKDF	A standard method for deriving separate cryptographic keys from shared key material.
HMAC	A keyed hash used to authenticate data when verifier and signer share a secret.
SHA-256	A cryptographic hash that produces a fixed-size fingerprint of data.
Ed25519	A public-key signature algorithm. A private key signs; the public key verifies.
Hash chain	Records linked by including the previous record's hash in the next record.
Tamper-evident	Modification can be detected during verification. It does not mean modification is impossible.
WORM	Write once, read many storage that prevents protected objects from being changed or deleted during their retention period.
Immutable retention	A storage policy that prevents overwrite or deletion for a defined period or legal hold.
Checkpoint	A signed summary of one or more chains' terminal hashes and sequence numbers at a point in time.
Anchoring	Keeping a checkpoint in a separate trust domain so later truncation or replacement can be detected.
Chain ID	Identifier for one independently ordered audit chain.
Sequence number	Increasing number used to detect missing or reordered records in a chain.
Key custody	The processes and systems that control who can use, rotate, revoke, and archive a private key.
Key fingerprint	A short hash-derived identifier used to distinguish one public key from another.
fsync	An operating-system request to flush file data toward durable storage; it is not a WORM guarantee.
Best-effort audit	Audit delivery that avoids blocking the request path and may drop records under pressure.
Required audit	Audit delivery that surfaces persistence failure instead of silently continuing.

Assurance, compliance, and measurement

Term	Plain-English meaning
Conformance specification	A versioned list of behaviors and report fields an implementation must test.
Test vector	A declared input and expected outcome used to check one behavior.
Negative control	A deliberately damaged or failing input used to prove that a test can detect failure.
OSCAL	NIST's machine-readable format for exchanging security-control and assessment information. It does not itself prove compliance.
NIST SP 800-53	A catalog of security and privacy controls used by many government and enterprise programs.
SOC 2	An independent examination of controls relevant to selected Trust Services Criteria over a defined scope and period.
HIPAA	A US health-information law and rule set whose obligations apply to covered entities, business associates, and their safeguards.
Audit evidence	Records and artifacts used to test whether a control was designed and operated as claimed.
OpenTelemetry / OTel	A standard way to generate and export traces, metrics, and logs.
p50 / p95 / p99	Latency percentiles. p95 means 95 percent of measured samples were at or below that value.
RSS	Resident set size, an operating-system measurement of process memory currently held in RAM.
In-process benchmark	Timing of selected code inside one process, excluding the complete network service path.
Confidence interval	A range expressing uncertainty around an estimate from repeated samples.