# Glossary ```{glossary} :sorted: AEAD See {term}`Authenticated Encryption With Associated Data`. AEAD Algorithm See {term}`Authenticated Encryption With Associated Data`. Algorithm Preferences The preferences for {term}`hash algorithms`, {term}`compression algorithms`, {term}`symmetric algorithms` and {term}`AEAD algorithms` are set using {term}`direct key signatures` or {term}`primary User ID` {term}`binding signatures`. See [](recipe-algorithm-preferences). Asymmetric Cryptography Asymmetric cryptography (also known as public-key cryptography) is used in OpenPGP to send messages without using a prior shared secret. For a more detailed discussion see [](public-key-cryptography). Authenticated Encryption With Associated Data Short AEAD, refers to an encryption scheme that ensures confidentiality of a message. Additionally, additional data, which is not confidential, may be associated with the message, ensuring integrity of both the confidential part of the message, as well as the additional data. See Wikipedia on [Authenticated Encryption](https://en.wikipedia.org/wiki/Authenticated_encryption). Authentication The process of {term}`validiting` an {term}`identity claim`. The term "authentication" here is semantically different from the one used in {term}`Authentication Key Flag`. Authentication Key Flag A {term}`Key Flag` which indicates that a {term}`Component Key` can be used to prove control over {term}`private key material` with a challenge-response mechanism. This is typically done to log into a remote system, often using the OpenSSH protocol. Note that the term "authentication" is used in a different context here than {term}`Authentication` of {term}`identity claims` that are associated with a {term}`certificate`. See [](key-flags). Authentication Tag See {term}`Message Authentication Code`. Authenticity See {term}`Authentication`. Back Signature See {term}`Primary Key Binding Signature`. Binary Signature A {term}`Data Signature` with the {term}`Signature Type ID` `0x00`, which is used for binary data. Binding The process of creating a {term}`Binding Signature` for a {term}`Component`, or the resulting {term}`Binding Signature`. See [](binding-signatures) for more. Binding Signature A {term}`self-signature` on a {term}`component` which associates that {term}`component` to the issuing {term}`component key` in a {term}`certificate`. See [](binding-signatures) for more. CA See {term}`Certification Authority`. Capability The operations an {term}`OpenPGP Component Key` can perform. See [](key-flags). Certificate See {term}`OpenPGP Certificate` Certificate Authority See {term}`Certification Authority` Certificate Holder A person or other entity, that holds an {term}`Transferable Secret Key` and thus is able to modify the accompanying {term}`OpenPGP Certificate`. Typically this is the owner of {term}`OpenPGP key`. Certification A certification, in OpenPGP, is a signature that makes a statement about an {term}`identity` in a {term}`certificate`, or an entire {term}`certificate`. Most commonly, the term is applied to "[third-party certifications](third-party-certifications)," in which an external actor indicates that they have {term}`validated` the link between an {term}`identity` and a {term}`certificate`. However, the term is also used for [self-signatures that bind identity components](bind-identity) to a {term}`certificate`. Certification Authority Also known as [Certificate authority](https://en.wikipedia.org/wiki/Certificate_authority), this is an entity that handles digital certificates, especially by signing or issuing them. Certification Key Flag A {term}`Key Flag`, indicating that a {term}`Component Key` can be used for issuing third-party {term}`certifications`. See [](key-flags). Certification Revocation Signature Packet An {term}`OpenPGP Signature Packet` to {term}`revoke` an earlier {term}`self-certification` of a {term}`User ID`. [RFC 5.2.1.13](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-certification-revocation-si) Certification Signature See {term}`Certification`. Certifying Self-Signature An {term}`OpenPGP Signature Packet` by the {term}`Certificate Holder` on an {term}`Identity Component` of their own {term}`Certificate`. Certifying Signature See {term}`Certification`. Cipher Type Byte This historical term was defined in [RFC 1991](https://datatracker.ietf.org/doc/html/rfc1991#section-4.1) and was subsequently superseded by {term}`Packet Tag` in [RFC 2440](https://datatracker.ietf.org/doc/html/rfc2440#section-4.2), which is in turn superseded by {term}`Packet Type ID` in the new [RFC](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-packet-headers). Cleartext Signature A {term}`Data Signature` which exists in a combined text format, encapsulating the (readable) text input it was created for. See [](cleartext-signature). Cleartext Signature Framework A framework for creating {term}`cleartext signatures`. See [RFC 7](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#cleartext-signature). Component An element in an {term}`OpenPGP Certificate`, that represents a {term}`component key` or {term}`identity component`. Component Key See {term}`OpenPGP Component Key`. Compressed Data Packet A packet containing a compressed {term}`OpenPGP Message` (typically a {term}`Literal Data Packet`). Compression See {term}`Data Compression`. Creation Time The point in time at which e.g. an {term}`OpenPGP Signature`, an {term}`OpenPGP Certificate`, or one of its {term}`component` is created. Creator See {term}`Issuer`. Criticality Flag A flag on {term}`Subpacket`s, that can mark them as critical or non-critical, which is has an influence on signature validation. See [](criticality-of-subpackets). Cryptographic Key A {term}`symmetric` or {term}`asymmetric` cryptographic key. See [](cryptography). Cryptographic Signature A raw cryptographic signature is an algorithm-specific sequence of bytes created by a {term}`Cryptographic Key`. CTB See {term}`Cipher Type Byte`. Data Compression The process of encoding information using fewer bits than the original representation. In OpenPGP data compression is used to reduce the size required for encrypted messages. See Wikipedia on [Data Compression](https://en.wikipedia.org/wiki/Data_compression). Data Signature {term}`Cryptographic signature` over binary documents or canonical text documents. See [](/signing_data). Data Signature Packet An {term}`OpenPGP Signature Packet` which describes a {term}`Data Signature`. See [](/signing_data). Delegation OpenPGP users can [delegate authentication decisions](delegation) to third parties, and thus rely on {term}`certifications` they issue. The remote party is then called a "{term}`trusted introducer`". This kind of delegation involves {term}`certifications` that include the {term}`trust signature` subpacket. Detached Signature A {term}`Data Signature` which exists separately to the data it was created for. See [](forms-of-data-signatures). Direct Key Signature Describes both a {term}`Signature Type ID`, as well as an according {term}`OpenPGP Signature` over a {term}`Primary Key`. Issued as a {term}`Self-Signature` it sets preferences and advertises {term}`features` applicable to an entire {term}`Certificate`. See [](direct-key-signature). Embedded Signature Subpacket An {term}`OpenPGP Signature Subpacket` which contains a complete {term}`OpenPGP Signature Packet`. See [RFC 5.2.3.34](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-embedded-signature) Encrypted Data Data that is encrypted. See [](/encryption). Encryption Key Flag A {term}`Key Flag`, indicating that a {term}`Component Key` can be used for encrypting data. See [](key-flags). There are two distinct encryption key flags, indicating that the key can encrypt communications, or data in long-term storage respectively. Expiration A mechanism by which a {term}`Component` is invalidated due to the {term}`Expiration Time` of its {term}`binding signature` being older than the {term}`Reference Time` by which it is validated. Expiration Time The time of expiry of an {term}`OpenPGP Signature Packet`. Features Subpacket An {term}`OpenPGP Signature Subpacket`, which denotes advanced OpenPGP features an {term}`implementation` supports. For an in-depth view on these {term}`subpackets` see [](zoom-dks). See [RFC 5.2.3.32](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-features) Fingerprint See {term}`OpenPGP Fingerprint`. Hard Revocation A {term}`Revocation Signature Packet` for a {term}`Certification` or a {term}`Component Key`, which either includes a {term}`Reason For Revocation Subpacket` with a {term}`Revocation Code`, that signifies the target being compromised (e.g., `0` or `2`), or has no {term}`Reason For Revocation Subpacket` at all. See [](hard-vs-soft-revocations). See [RFC 5.2.3.31](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-reason-for-revocation). Hash Algorithm See {term}`Hash Function`. Hash Digest Output of a cryptographic hash function for a string of data of any length. See [](cryptographic-hash). Hash Function A function used to map data of arbitrary size to fixed-size values (see {term}`Hash Digest`). Hash Value See {term}`Hash Digest`. Hashed Area An area in an {term}`OpenPGP Signature Packet` containing {term}`OpenPGP Signature Subpacket`s, that is covered by the {term}`Hash Digest` a {term}`Cryptographic Signature` is created for. See [](subpacket-areas). Hashed Subpacket An {term}`OpenPGP Signature Subpacket` residing in the {term}`Hashed Area` of an {term}`OpenPGP Signature Packet`. Hybrid Cryptosystem A cryptographic system that employs both {term}`Asymmetric Cryptography` and {term}`Symmetric Cryptography`. See [](hybrid-cryptosystems). Identity An identity of a {term}`Certificate Holder`. It is represented by an {term}`Identity Component`, which may be certified using {term}`identity certifications`, or by a {term}`Notation`. Identity Certification An {term}`OpenPGP Signature Packet` on an {term}`Identity Component` which {term}`certifies` its {term}`authenticity`. Identity certifications can be issued either: - by the certificate holder, as a {term}`self-signature`, or - by a third party, as a {term}`third-party identity certifications`. Identity Claim A {term}`Certificate Holder` may use {term}`Identity Components` or {term}`Notations` to state a claim about their {term}`Identity`. Identity Component Part of an {term}`OpenPGP Certificate`, that is used to associate data about the {term}`Certificate Holder` with it. See [](identity-components) for further details. Identity Verification A process by which the {term}`Identity Claim` of a {term}`Certificate Holder` is verified. See also {term}`Signature Verification`. Initial Introducer An {term}`OpenPGP Certificate` explicitly {term}`delegated` to from a {term}`Trust Anchor`. Inline Signature A {term}`Data Signature` which exists encapsulated alongside the data it was created for in an OpenPGP container. See [](forms-of-data-signatures). Issuer An entity, that created an {term}`OpenPGP Signature Packet` using a {term}`Transferable Secret Key`. Issuer Fingerprint Subpacket A {term}`Subpacket` specifying the {term}`Fingerprint` of an {term}`Issuer Key`. See [RFC 5.2.3.35](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-issuer-fingerprint) Issuer Key The {term}`OpenPGP Component Key` of an {term}`Issuer`, used to create an {term}`OpenPGP Signature Packet`. Key In OpenPGP, and cryptography more generally, the term "key" holds different meanings. First, it can apply to different [cryptographic primitives](/cryptography): - asymmetric public key - asymmetric private key - {term}`Symmetric Secret Key` Additionally, in OpenPGP, asymmetric cryptographic keys are used on [three different layers](layers-of-keys-in-openpgp) of abstraction: - cryptographic key - OpenPGP component key - {term}`OpenPGP key` (which in turn refers to either an {term}`OpenPGP Certificate` or a {term}`Transferable Secret Key` Key Expiration Time Subpacket An {term}`OpenPGP Signature Subpacket Type` which defines the {term}`Expiration Time` for a {term}`key`. See [RFC 5.2.3.13](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-key-expiration-time) Key Flag A preference encoded in an {term}`OpenPGP Signature Subpacket`, that defines the {term}`Capability` a {term}`OpenPGP Component Key` has. See [](signature-subpackets). Key Holder See {term}`Certificate Holder`. Key ID The high-order (leftmost) 64 bits of an {term}`OpenPGP Fingerprint`. Historically, this term refers to the low-order (rightmost) 64 bits of an {term}`OpenPGP Fingerprint`. Key Material May refer to {term}`Public Key Material` or {term}`Private Key Material`. Key Owner See {term}`Certificate Holder`. Key Revocation Signature Packet A {term}`Revocation Self-signature` for an entire {term}`OpenPGP Certificate`. Key Server A service available over the network, which provides access to {term}`OpenPGP Certificates` e.g., by searching for an {term}`OpenPGP Fingerprint` or {term}`User ID`, via the `HKP` and/ or `HKPS` protocols. Several implementations such as [hagrid](https://gitlab.com/keys.openpgp.org/hagrid/), or [hockeypuck](https://github.com/hockeypuck/hockeypuck) exist. Life-cycle Management In OpenPGP several actions are necessary for the prolonged use of an {term}`OpenPGP Certificate` or adapting its {term}`components` to the requirements of the {term}`Certificate Holder`. These are for example changes to {term}`binding signatures` (adding or {term}`revocation` of {term}`component keys` or {term}`direct key signature`), modification of {term}`expiration time` or other {term}`metadata` for {term}`components`. See [](self-signatures). Literal Data Packet A {term}`packet` which contains the plaintext data of an encrypted and/or signed message. See [RFC 5.9](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#lit) for more details. MAC See {term}`Message Authentication Code`. Master Key See {term}`OpenPGP Primary Key`. Message Authentication Code A piece of information used for integrity and {term}`authenticity` verification of a message. See [](message-authentication-code). Meta Introducer An {term}`OpenPGP Certificate` that acts as a {term}`Trusted introducer` and has a {term}`Trust Depth` greater than one. A meta introducer can introduce other (meta-) {term}`introducers`. Metadata Data related to preferences of an {term}`OpenPGP Certificate` or its {term}`Certificate Holder`, that can be found in {term}`signature` {term}`packets`. See [](metadata-in-certificates). Notation A mechanism for a {term}`Certificate Holder` to provide user-defined data using a {term}`Notation Signature Subpacket`. Notation Signature Subpacket An {term}`OpenPGP Signature Subpacket` which is used to add user-defined data to a {term}`Certificate`. See [](notation-signature-subpackets). Notation Tag Part of a {term}`Notation` name. One-pass Signature Packet One or more {term}`packets` before the actual data in a {term}`Data Signature` which contain information to allow a receiving {term}`implementation` to create {term}`hashes` required for signature verification. See [RFC 5.4](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#one-pass-sig) for more details. OpenPGP Certificate An OpenPGP certificate contains public key material, identity claims and third party certifications (but no private key material) OpenPGP Component Key An {term}`OpenPGP Primary Key` or {term}`OpenPGP Subkey`. For an in-depth discussion see [](component-keys). OpenPGP Fingerprint An OpenPGP Fingerprint is a shorthand representation of an {term}`OpenPGP Component Key`. Fingerprints effectively act as unique identifiers. See [](fingerprint). The Fingerprint of the {term}`primary component key` is used as an identifier for the full {term}`OpenPGP Certificate`. OpenPGP Implementation A piece of software implementing the OpenPGP protocol (to some extend). OpenPGP Key Used either for an {term}`OpenPGP Certificate` (containing public key material and metadata), or for an {term}`OpenPGP Private Key`. See [](/certificates) for an in-depth discussion. OpenPGP Message A data structure, which contains OpenPGP packets, such as {term}`literal`, {term}`compressed`, {term}`encrypted` or {term}`signed` data. OpenPGP Public Key See {term}`OpenPGP Certificate`. OpenPGP Private Key See {term}`Transferable Secret Key`. OpenPGP Primary Key An {term}`OpenPGP Component Key` that is used in the primary key role of an {term}`OpenPGP Certificate`. For a more detailed discussion, see [](primary-key). OpenPGP Signature See {term}`OpenPGP Signature Packet`. OpenPGP Signature Packet A {term}`packet` that contains a raw {term}`cryptographic signature`, a {term}`Signature Type ID` and additional {term}`metadata`. See [](/signatures). Basic concepts are introduced in [](/signatures) and more detailed use-cases are explained in [](/signing_data) and [](/signing_components). OpenPGP Signature Subpacket A data structure in a {term}`Signature Packet`, that describes {term}`metadata` and preferences. See [](signature-subpackets). OpenPGP Signature Subpacket Type An {term}`OpenPGP Signature Subpacket` type. OpenPGP Signature Type The type of an {term}`OpenPGP Signature Packet` is defined by its {term}`Signature Type ID`. See [](signature-types). OpenPGP Signing Subkey An {term}`OpenPGP Subkey` with the {term}`Signing Key Flag`. OpenPGP Subkey An {term}`OpenPGP Component Key` that is used in the subkey role, in an {term}`OpenPGP Certificate`. For a more detailed discussion, see [](subkeys). Owner See {term}`Certificate Holder`. Packet An element in an {term}`OpenPGP Certificate` or {term}`OpenPGP Message`. Packet Header A section of variable length at the beginning of a {term}`Packet`, which encodes for example the {term}`Packet Type ID`. See the relevant [section in the RFC](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-packet-headers), which explains this section in more detail. Packet Tag This historical term was defined in [RFC 2440](https://datatracker.ietf.org/doc/html/rfc2440#section-4.2) and is superseded by {term}`Packet Type ID` in the new [RFC](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-packet-headers). Packet Type ID A numerical value encoded in the first octet of a {term}`Packet Header`, defining a {term}`Packet`'s type. Positive Certification An {term}`OpenPGP Signature Type` with the {term}`Signature Type ID` `0x13`, which is used in {term}`binding signatures` for {term}`User IDs`. This {term}`OpenPGP Signature Type` implies that the {term}`issuer` has done substantial {term}`verification` of the {term}`Identity Claim`. See [](bind-identity). Preferred Compression Algorithms Subpacket An {term}`OpenPGP Signature Subpacket Type` which defines the preferred {term}`compression algorithms` for an {term}`OpenPGP Certificate` or {term}`Component Key`. This defines which {term}`algorithms` the {term}`key holder` prefers to receive. See [RFC 5.2.3.17](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-preferred-compression-algor). Preferred Hash Algorithms Subpacket An {term}`OpenPGP Signature Subpacket Type` which defines the preferred {term}`hash algorithm` for an {term}`OpenPGP Certificate` or {term}`Component Key`. This defines which algorithms the {term}`key holder` prefers to receive. See [RFC 5.2.3.16](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-preferred-hash-algorithms). Preferred Symmetric Ciphers for v1 SEIPD Subpacket An {term}`OpenPGP Signature Subpacket Type` which defines the preferred version 1 {term}`SEIPD` algorithms for an {term}`OpenPGP Certificate` or {term}`Component Key`. This defines which algorithms the {term}`key holder` prefers to receive and implicitly signifies the supported algorithms of the {term}`key holder`'s {term}`implementation`. See [RFC 5.2.3.14](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-preferred-symmetric-ciphers). Preferred AEAD Ciphersuites Subpacket An {term}`OpenPGP Signature Subpacket Type` which defines the preferred version 2 {term}`SEIPD` algorithms for an {term}`OpenPGP Certificate` or {term}`Component Key`. This defines which algorithms the {term}`key holder` prefers to receive and implicitly signifies the supported algorithms of the {term}`key holder`'s {term}`implementation`. See [RFC 5.2.3.15](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-preferred-aead-ciphersuites) Primary Component Key See {term}`OpenPGP Primary Key`. Primary Introducer See {term}`Initial Introducer`. Primary Key See {term}`OpenPGP Primary Key`. Primary Key Binding Signature A {term}`Binding Signature`, which is created by a {term}`OpenPGP Signing Subkey` on the {term}`OpenPGP Primary Key` of an {term}`OpenPGP Certificate` and stored in an {term}`Embedded Signature Subpacket` in the {term}`Binding Signature` for the {term}`OpenPGP Signing Subkey`. This special case is explained in more detail in [](bind-signing-subkey). Primary User ID A {term}`User ID` which carries the default preferences for {term}`identity components` without preferences. See [](primary-user-id). Primary User ID Subpacket An {term}`OpenPGP Signature Subpacket` used in {term}`User ID self-signatures` which allows to signify whether the {term}`User ID` in question is considered a {term}`Primary User ID`. See [RFC 5.2.3.27](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#primary-user-id-subpacket) Primary User ID Binding Signature A {term}`Binding Signature`, which is created by an {term}`OpenPGP Primary Key` to bind a {term}`User ID` to its {term}`OpenPGP Certificate` and marking it as the {term}`Primary User ID`. This {term}`Binding Signature` may carry {term}`metadata` specific to the {term}`User ID` at hand as well as some applicable to the entire {term}`OpenPGP Certificate`. See [](primary-user-id-binding). Private Key See {term}`Transferable Secret Key`. Private Key Material A raw cryptographic private key. Public Key See {term}`OpenPGP Public Key`. Public Key Algorithm An {term}`asymmetric cryptographic` algorithm. See [](public-key-cryptography). Public Key Cryptography See {term}`Asymmetric Cryptography`. Public Key Material See {term}`OpenPGP Certificate`. Reason For Revocation Subpacket An {term}`OpenPGP Signature Subpacket`, which is used in {term}`Certification Revocation Signature Packet` and {term}`key revocation signature packets` to describe a reason for the {term}`revocation`. See [RFC 5.2.3.31](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-reason-for-revocation) Reference Time A point in time at which an {term}`OpenPGP Certificate` or {term}`OpenPGP Signature` is evaluated. Regular Expression Subpacket An {term}`OpenPGP Signature Subpacket` which allows for limiting {term}`delegations` to {term}`identities` matching a regular expression. Revocation Mechanism to invalidate a {term}`component` or an entire {term}`OpenPGP Certificate` using a {term}`Revocation Self-signature`. See [](revocations). Revocation Certificate A {term}`Revocation Self-signature` for an {term}`OpenPGP Primary Key` distributed alongside the plain {term}`OpenPGP Primary Key`. See [RFC 10.1.2](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-openpgp-v6-revocation-certi) Note that in [OpenPGP v4 this term is typically used](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#section-10.1.3-6) for a bare {term}`Revocation Self-signature` {term}`packet`. Revocation Code A number in a {term}`Reason For Revocation Subpacket` which represents the reason for a {term}`Revocation`. Revocation Self-signature A class of {term}`self-signatures` to {term}`revoke` {term}`primary keys`, {term}`User IDs` or {term}`User Attributes` and invalidate {term}`subkey binding signatures`. See [](self-revocations). Revocation Signature See {term}`Revocation Signature Packet`. Revocation Signature Packet An {term}`OpenPGP Signature Packet` used for the {term}`revocation` of a {term}`certification` or {term}`binding`. Revocation signatures are often {term}`self-signatures`, more specifically {term}`revocation self-signatures`. However, *{term}`certification revocations`* can be both {term}`self-signatures` or {term}`third-party signatures`. Additionally, with the deprecated *Revocation Key* mechanism, {term}`third-party` *Key-* and *Subkey revocations* also exist. RFC This document, unless noted otherwise, refers to the [OpenPGP version 6 specification](https://datatracker.ietf.org/doc/draft-ietf-openpgp-crypto-refresh/) when referring to *RFC*. SEIPD See {term}`Symmetrically Encrypted Integrity Protected Data`. Self-certification A {term}`certification` on a {term}`component` of an {term}`OpenPGP Certificate` issued by a {term}`component key` of the same {term}`OpenPGP certificate`. Secret Key Material See {term}`Private Key Material`. Self-signature An {term}`OpenPGP Signature Packet` by the {term}`Certificate Holder` on a {term}`Component` of their own {term}`Certificate`. Session Key A unique shared secret used in encryption in a {term}`Hybrid Cryptosystem`. See [](encryption) and [](decryption). Soft Revocation A {term}`Revocation Signature Packet` for a {term}`Certification` or a {term}`Component Key`, which includes a {term}`Reason For Revocation Subpacket` with a {term}`Revocation Code`, that does not signify the target being compromised (e.g., `0` or `2`). See [](hard-vs-soft-revocations). See [RFC 5.2.3.31](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-reason-for-revocation). Signature See {term}`OpenPGP Signature Packet`. Signature Creation Time Subpacket An {term}`OpenPGP Signature Subpacket Type` which defines the {term}`Creation Time` for an {term}`OpenPGP Signature Packet`. See [RFC 5.2.3.11](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-signature-creation-time) Signature Expiration Time Subpacket An {term}`OpenPGP Signature Subpacket Type` which defines the {term}`Expiration Time` for an {term}`OpenPGP Signature Packet`. See [RFC 5.2.3.18](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-signature-expiration-time) Signature On Component {term}`Cryptographic signature` associated with {term}`Component Keys` or {term}`Identity Components`. See [](/signing_components). Signature Over Data See {term}`Data Signature`. Signature Packet See {term}`OpenPGP Signature Packet`. Signature Subpacket See {term}`OpenPGP Signature Subpacket`. Signature Subpacket Type See {term}`OpenPGP Signature Subpacket Type`. Signature Type See {term}`OpenPGP Signature Type`. Signature Type ID A numerical identifier for a {term}`Signature Type`. Signature Verification In cryptography the mechanism of verification relates to a process in which a claim (i.e., a {term}`signature`) is tested (i.e., using the relevant {term}`components` of a {term}`certificate`). Signer A {term}`Certificate Holder`, that is able to create {term}`self-signatures` and {term}`third-party signatures`. Signing-capable See {term}`Signing Key Flag`. Signing Key Flag A {term}`Key Flag`, indicating that a {term}`Component Key` can be used for signing data. See [](key-flags). Signing Subkey See {term}`OpenPGP Signing Subkey`. Strong Authentication "Strong Authentication" in this text refers to having ascertained that a {term}`certificate` and an {term}`identity claim` on it are legitimately linked. That is, that the person who controls the {term}`certificate` is correctly represented by the {term}`identity component`. Strong authentication in OpenPGP is typically encoded with a {term}`certification signature`. Ascertaining strong authentication requires an out-of-band check: Either via a manual {term}`verification` process, or an automated system that can {term}`certify` that a user has identified to the system that issues the {term}`identity` in question (e.g. an email provider can {term}`certify` email-based {term}`identities` that it issues to the user). Also see {term}`Authentication`. Subkey See {term}`OpenPGP Subkey`. Subkey Binding Signature A {term}`Self-signature` to associate an {term}`OpenPGP Subkey` with an {term}`OpenPGP Primary Key`. See [](bind-subkey). Subkey Revocation Signature Packet A {term}`Self-signature` to {term}`revoke` an {term}`OpenPGP Subkey` in an {term}`OpenPGP Certificate`. See [RFC 5.2.1.12](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-subkey-revocation-signature) Subpacket See {term}`OpenPGP Signature Subpacket`. Subpacket Type See {term}`OpenPGP Signature Subpacket Type`. Symmetric Cryptography Symmetric cryptography is used in OpenPGP. For a more detailed discussion see [](symmetric-key-cryptography). Symmetrically Encrypted Integrity Protected Data Short *SEIPD*, this refers to {term}`Symmetric Cryptography` based encrypted data, which is used in a Symmetrically Encrypted Integrity Protected Data Packet. See [RFC 5.13](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-symmetrically-encrypted-int). Symmetric Secret Key The {term}`Private Key Material` used in {term}`Symmetric Cryptography`. Text Signature A {term}`signature packet` with the {term}`Signature Type ID` `0x01`, which is used for textual data. Third-party Identity Certification {term}`Certification` by third-parties to confirm ownership of an {term}`OpenPGP Certificate` ({term}`Identity Claim`) by a {term}`Certificate Holder`. See [](third-party-identity-certifications). Third-party Signature A {term}`Signature` by a third-party on a {term}`Component` of a {term}`Certificate`. Transferable Secret Key A Transferable Secret Key (TSK) is the combination of an {term}`OpenPGP Certificate` and the associated {term}`private key material`. Also often referred to as an "OpenPGP private key". It is discussed in detail in [](/private_keys). Trust Amount A numerical value between `0` and `255`, stored in {term}`trust signatures` used for indicating the degree of reliance on the {term}`delegation`. Values less than `120` indicate partial trust, values equal to or greater than `120` indicate complete trust. See [](trust-amount). See [RFC 5.2.3.21](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-trust-signature) Trust Anchor An entity in a {term}`Trust Model` for which trust is assumed and not derived. Trust Depth This numerical value is part of a {term}`Trust Signature` and describes the extent of trustworthiness of a {term}`Certification`, that the {term}`signer` assigns to it. See [](trust-level). Trust Level See {term}`Trust Depth`. Trust Model A model by which trust between {term}`identities` associated with different {term}`OpenPGP Certificates` is created. See [](third-party-identity-certifications). Trust Root See {term}`Trust Anchor`. Trust Signature The *trust signature* {term}`subpacket` on a {term}`certifying signature` is used for {term}`delegation` of {term}`authentication` decisions. With this feature, an OpenPGP user can designate a {term}`certificate` as a "{term}`trusted introducer`" and opt to rely on {term}`certifications` they issue. See [RFC 5.2.3.21](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-trust-signature) Trusted introducer OpenPGP users can choose to rely on {term}`certifications` issued by a third party. The remote party of such a {term}`delegation` is called a "trusted introducer". See [](delegation) for more details. TSK See {term}`Transferable Secret Key`. tsig See {term}`Trust signature` Type ID See {term}`Signature Type ID`. Unhashed Area An area in a {term}`Signature Packet` containing {term}`Signature Subpacket`s, that is *not* covered by the {term}`Hash Digest` a {term}`Cryptographic Signature` is created for. See [](subpacket-areas). Unhashed Subpacket A {term}`Signature Subpacket` residing in the {term}`Unhashed Area` of a {term}`Signature Packet`. User Attribute An {term}`Identity Component`, which may hold complex attribute data, e.g. a single JPEG image. See [](user-attributes). User ID An {term}`Identity Component`, which describes an {term}`Identity` of a {term}`Certificate Holder`. See [](user-ids). User ID Binding Signature A {term}`Binding Signature`, which is created by an {term}`OpenPGP Primary Key` to bind a {term}`User ID` to an {term}`OpenPGP Certificate`. Validation A mechanism by which the [operational needs of a use-case are met](https://en.wikipedia.org/wiki/Verification_and_validation#Validation). In OpenPGP terminology this may refer to processes such as ensuring, that an {term}`OpenPGP Signature Packet` has been created after a {term}`Transferable Secret Key`'s {term}`Creation Time`, but before its {term}`Expiration Time`. Validity See {term}`Validation`. Verification A mechanism by which the [compliance with design specifications are met](https://en.wikipedia.org/wiki/Verification_and_validation#Verification). In OpenPGP terminology this may refer to e.g. {term}`Signature Verification` or {term}`Identity Verification`. Web Of Trust A {term}`trust model` which is based on a network of {term}`certifications` and {term}`delegations`, that can be used to discern the reliability of {term}`certificates` and their associated {term}`identities`. See [](wot). ```