Glossary

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Glossary terms and definitions last updated: August 19, 2024

This Glossary is an aggregation of terms and definitions specified in NIST's cybersecurity and privacy standards, guidelines, and other technical publications, and in CNSSI 4009. These should not be viewed as "official" or "preferred" definitions for a particular subject area, sector, or industry, with the exception that some definitions are cited directly from U.S. laws, the Code of Federal Regulations, Presidential Directives, etc.

Each term-definition pair must be understood within the context of its Source document, to which readers should refer. Because of this, many terms have multiple, varying definitions that reflect the different contexts of various publications written at different times.

Cite the source publication, not this website. As our documents are published and withdrawn, the terminology on these web pages will change. When citing terms and definitions, we encourage you to cite the source publication for the authoritative terminology and to understand it in its proper context. Many terms on this website have different definitions, from multiple publications.
Inclusive language. Some existing NIST publications may contain potentially biased or confusing terminology. As we develop and revise publications, we follow NIST's inclusive language guidance.
Public input. We invite public comments—including terminology suggestions—on our draft publications and welcome your contributions.
Artificial Intelligence (AI) terminology. For AI-focused terminology, see the Glossary available from the NIST Trustworthy & Responsible AI Resource Center.

For more background about this Glossary, see NISTIR 7298 Rev. 3.
Download the Glossary in JSON format (updated daily at 6:15 pm ET; see metadata).

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Showing 485 matching records.

(r, s)

3rd Generation

R&D

R/W

RACE Integrity Primitives Evaluation Message Digest

RAdAC

Radial Basis Function

Radio Access Network

Radio Resource Control

Radio Technical Commission for Aeronautics

Radio-Frequency Identification

Radiology Information System

Radionuclide Transportation Agency

RAID

RAIM

RAM

RAMPS

RAN

RAND

Random Access Machine

Random Access Memory

Random Binary Sequence

Random bit

Random Bit Generator (RBG)

Random Excursion Test

Random Excursion Variant Test

Random Field

random forest classification

Random Forests

Random nonce

Random Number

random number generation

random number generator (RNG)

random oracle model

Random Parameter

Random value

Random Variable

Randomized hashing

Randomized message

randomizer

Randomness extraction

Randomness Source

Range

Rank (of a matrix)

rank syndrome decoding

Rank Test

RAP

RAPI

Rapid elasticity

RAR

RARP

RAS

Rate

Rationale

Raw data

RBAC

RBF

RBG

RBG seed

RC.CO

RC4

RCFL

RCP

RCS

RDBMS

RDMA

RDP

RDR

RDS

RE(f)

Lesen

Read/Write

Read/Write/Execute

Reader

Reader Spoofing

Reader Talks First

Read-Only Memory

Real Mode

real time

Real Time Clock

real time reaction

Really Simple Syndication

Realm Management Extension

Real-Time Inter-Network Defense

Real-Time Locating Systems

Real-Time Location System

Real-Time Operating System

Re-authentication

Received Signal Strength Indication

Receiver

Receiver Address

receiver autonomous integrity monitoring

recipient

Recipient-usage period

Reciprocal Agreement

reciprocity

Recommendation

Record

record-matching probability

records

records management

Recover

recover (CSF function)

Recover, Communications

Recovery Point Objective

recovery procedures

Recovery Time Objective

RED

RED data

RED equipment

Red Hat Enterprise Linux

Red Hat Package Manager

RED key

RED line

RED optical fiber line

RED signal

Red Team

red team exercise

Red Team/Blue Team Approach

RED wireline

RED/BLACK concept

redaction

Reduced Instruction Set Computer

Reduced Instruction Set Computing

Redundant Array of Independent Disks

redundant control server

REE

Reference

Reference Architecture

Reference Data Set

Reference Document

Reference Document Element

Reference Integrity Manifest

reference monitor

reference monitor concept

reference validation mechanism

Reference Version

regenerative cyber defense

Regional Alliances and Multistakeholder Partnerships to Stimulate

Regional Computer Forensics Laboratory

Regional Internet Registry

Registered application provider IDentifier

Registrar

registration

Registration agent

registration authority (RA)

Registration authority (RA)

Registry

regrader

Regular Expression

re-identification

re-identification precision

re-identification probability

re-identification rate

re-identification risk

Rekey

re-key (a certificate)

Relational DataBase Management System

Relationship

Relationship Explanation

Relationship Identifier

Relationship Property

relationship style

Relationship Type

Relatively prime

relay

Relay Node

Release

release prefix

Releasing Unverified Plaintext

relevant event

reliability

Reliability, Maintainability, Availability

Reliable Datagram Sockets

relying party

remanence

remediation

Remote

remote access

Remote Access Server

Remote Application Programming Interface

Remote Copy Protocol

Remote Desktop Protocol

remote diagnostics

remote diagnostics/ maintenance

Remote Direct Memory Access

remote maintenance

Remote Method Invocation

Remote Monitoring

Remote Patient Monitoring

Remote Procedure Call

remote rekeying

Remote Shell

Remote Switched Port Analyzer

Remote Synchronization

remote terminal unit

Remotely Triggered Black-Holing

removable media

removable media device

Removable User Identity Module (R-UIM)

REN-ISAC

Repeatability

Replace

replay attack

replay resistance

reporter

Reporting

Representational State Transfer (REST)

Representative (of a key owner)

Reproducibility

Request for Comments

Request for Comments (IETF standards document)

Request for Information

Request for Proposal

Requester

required

requirement

requirements engineering

Requirements Verification Traceability Matrix

RES

Research and Development

Research and Education Networking Information Sharing and Analysis Center

Reseaux IP Europeens

Reseaux IP Europeens Network Coordination Centre

reserve keying material

Reserved for Future Use

resident alien

residual information protection

residual risk

residue

resilience

Resilience Management Model

Resilience Requirements

Resilient Interdomain Traffic Exchange

resilient otherwise

Resilient Systems Working Group

Resolvable Private Address

Resolver

resource

Resource Access Point

Resource allocation

resource consumer

resource manager

Resource pooling

resource provider

Resource Public Key Infrastructure

Resource Record

Resource Record Signature

Resource Server

Resource-Oriented Lightweight Information Exchange

Respond

respond (CSF function)

Respond, Communications

Response

Response Rate Limiting

responsibility to provide

Responsible Person

REST

restoration

restricted data

Result content

RESULTn

results

Retention period

retirement

Return on Investment

Return Oriented Programming

Reverse Address Resolution Protocol

Reverse Channel

Reverse SOAP

Review Status

Review Techniques

revocation

Revoked Key Notification

Revoked key notification (RKN)

Reward system

RF Subsystem

RFC

RFD

RFI

RFID

RFP

RFU

RHEL

RIB

Ribonucleic Acid

Rich Communication Services

Rich Execution Environment

Rich Site Summary or Really Simple Syndication

RID

RIDR

rightmost (V, a)

Rijndael

RIM

Ring Learning With Rounding

RIP

RIPE

RIPE NCC

RIPEMD

Ripple

RIR

RIS

RISC

risk

Risk Adaptive (Adaptable) Access Control

risk aggregation

risk analysis

Risk Appetite

risk assessment

Risk Assessment Methodology

risk assessment report (RAR)

risk assessor

risk criteria

Risk Detail Record

Risk Detail Report

risk elevation

risk escalation

risk evaluation

risk executive (function)

Risk Executive Function

risk factor

risk framing

risk governance

risk identification

risk management

Risk Management Council or Committee

risk management framework (RMF)

Risk Management Framework (RMF) step

risk management level

Risk Management Process

risk management strategy

risk mitigation

risk model

risk optimization

Risk Profile

Risk Register

Risk Reserve

risk response

Risk Response Measure

risk response plan

risk tolerance

risk treatment

RITE

Rivest Cipher 4

Rivest-Shamir-Adleman

RKN

RLP

RLS

RLWR

RMA

RMC

RME

RMF

RMI

RMM

RMON

RMP

RNA

RNG

RNG seed

ROA

Robot Operating System

Robust Inter-Domain Routing

Robust Security Network Information Element

robustness

ROE

Rogue Device

ROI

role

role-based access control (RBAC)

Role-based authentication

Roles and Responsibilities

ROLIE

Rollup

ROM

Root Cause Analysis

Root Certificate

Root Certificate Authority (CA)

Root Key

Root of Trust for Measurement

Root of Trust for Reporting

Root of Trust for Storage

Root of Trust for Update

Root of Trust for Update verification component

root user

rootkit

roots of trust

ROP

ROS

RoT

Rotate

ROTs

Rough Order of Magnitude

Round

Round key

Round robin consensus model

Route Flap Damping

Route Leak Protection

Route Origin Attestation

Route Origin Authorization

Route Origin Validation

router

Router Under Test

Routing Information Base

Routing Information Protocol

ROV

Row Level Security

RPC

RPKI

RPKI cache to router protocol

RPKI Repository Delta Protocol

RPKI Validation Cache

RPKI-to-router protocol

RPM

RPO

RRC

RRDP

RRL

RRSIG

RS.CO

RS2

RS2 Technologies

RSA

RSA Secret Value Encapsulation

RSA Signature Scheme with Appendix - Probabilistic Signature Scheme

RSA with Optimal Asymmetric Encryption Padding

RSA-OAEP

RSASVE

RSD

RSH

RSN

RSNA

RSNIE

RSPAN

RSS

RSSI

RSWG

rsync

RTA

RTBH

RTC

RTCA

RTF

RTLS

RTM

RTO

RTOS

RTR

RTS

RTU

RTU-V

Rule

Rule-Based Event Correlation

rule-based security policy

Rules of Engagement (ROE)

ruleset

Run

Run (of output sequences)

Runs Test

runtime

RUP

RUT

rv[0…b]

rv_length_indicator

RVC

RVTM

RWX

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