1.1 Glossary

This document uses the following terms:

Active Directory: A general-purpose network directory service. Active Directory also refers to the Windows implementation of a directory service. Active Directory stores information about a variety of objects in the network. User accounts, computer accounts, groups, and all related credential information used by the Windows implementation of Kerberos are stored in Active Directory. Active Directory is either deployed as Active Directory Domain Services (AD DS) or Active Directory Lightweight Directory Services (AD LDS). [MS-ADTS] describes both forms. For more information, see [MS-AUTHSOD] section, Lightweight Directory Access Protocol (LDAP) versions 2 and 3, Kerberos, and DNS.

Authentication Protocol (AP) exchange: The Kerberos subprotocol called the "authentication protocol", sometimes referred to as the "Client/Server Authentication Exchange", in which the client presents a service ticket and an authenticator to a service to establish an authenticated communication session with the service (see [RFC4120] section 3.2).

Authentication Service (AS): A service that issues ticket granting tickets (TGTs), which are used for authenticating principals within the realm or domain served by the Authentication Service.

Authentication Service (AS) exchange: The Kerberos subprotocol in which the Authentication Service (AS) component of the key distribution center (KDC) accepts an initial logon or authentication request from a client and provides the client with a ticket-granting ticket (TGT) and necessary cryptographic keys to make use of the ticket. This is specified in [RFC4120] section 3.1. The AS exchange is always initiated by the client, usually in response to the initial logon of a principal such as a user.

authenticator: When used in reference to Kerberos, see Kerberos authenticator.

authorization data: An extensible field within a Kerberos ticket, used to pass authorization data about the principal on whose behalf the ticket was issued to the application service.

claim: An assertion about a security principal expressed as the n-tuple {Identifier, ValueType, m Value(s) of type ValueType} where m is greater than or equal to 1. A claim with only one Value in the n-tuple is called a single-valued claim; a claim with more than one Value is called a multi-valued claim.

Compound identity TGS-REQ: A FAST TGS-REQ that uses explicit FAST armoring using the computer's ticket-granting ticket (TGT).

datagram: A style of communication offered by a network transport protocol where each message is contained within a single network packet. In this style, there is no requirement for establishing a session prior to communication, as opposed to a connection-oriented style.

directory: The database that stores information about objects such as users, groups, computers, printers, and the directory service that makes this information available to users and applications.

directory service (DS): A service that stores and organizes information about a computer network's users and network shares, and that allows network administrators to manage users' access to the shares. See also Active Directory.

distinguished name (DN): A name that uniquely identifies an object by using the relative distinguished name (RDN) for the object, and the names of container objects and domains that contain the object. The distinguished name (DN) identifies the object and its location in a tree.

domain: A set of users and computers sharing a common namespace and management infrastructure. At least one computer member of the set must act as a domain controller (DC) and host a member list that identifies all members of the domain, as well as optionally hosting the Active Directory service. The domain controller provides authentication of members, creating a unit of trust for its members. Each domain has an identifier that is shared among its members. For more information, see [MS-AUTHSOD] section and [MS-ADTS].

domain controller (DC): The service, running on a server, that implements Active Directory, or the server hosting this service. The service hosts the data store for objects and interoperates with other DCs to ensure that a local change to an object replicates correctly across all DCs. When Active Directory is operating as Active Directory Domain Services (AD DS), the DC contains full NC replicas of the configuration naming context (config NC), schema naming context (schema NC), and one of the domain NCs in its forest. If the AD DS DC is a global catalog server (GC server), it contains partial NC replicas of the remaining domain NCs in its forest. For more information, see [MS-AUTHSOD] section and [MS-ADTS]. When Active Directory is operating as Active Directory Lightweight Directory Services (AD LDS), several AD LDS DCs can run on one server. When Active Directory is operating as AD DS, only one AD DS DC can run on one server. However, several AD LDS DCs can coexist with one AD DS DC on one server. The AD LDS DC contains full NC replicas of the config NC and the schema NC in its forest. The domain controller is the server side of Authentication Protocol Domain Support [MS-APDS].

Domain Name System (DNS): A hierarchical, distributed database that contains mappings of domain names to various types of data, such as IP addresses. DNS enables the location of computers and services by user-friendly names, and it also enables the discovery of other information stored in the database.

FAST armor: Using a ticket-granting ticket (TGT) for the principal to protect Kerberos messages, as described in [RFC6113].

Flexible Authentication Secure Tunneling (FAST): FAST provides a protected channel between the client and the Key Distribution Center (KDC).

fully qualified domain name (FQDN): An unambiguous domain name that gives an absolute location in the Domain Name System's (DNS) hierarchy tree, as defined in [RFC1035] section 3.1 and [RFC2181] section 11.

Generic Security Services (GSS): An Internet standard, as described in [RFC2743], for providing security services to applications. It consists of an application programming interface (GSS-API) set, as well as standards that describe the structure of the security data.

integrity level: The attributed trustworthiness of an entity or object.

Internet host name: The name of a host as defined in [RFC1123] section 2.1, with the extensions described in [MS-HNDS].

Kerberos authenticator: A record sent with a ticket to a server to certify the client's knowledge of the session key in the ticket; to help the server detect replay attacks by proving that the authenticator is recently constructed; and to help the two parties select additional session keys for a particular connection authenticated by Kerberos. The use of authenticators, including how authenticators are validated, is specified in [RFC4120] section 5.5.1. For more information, see [KAUFMAN].

Kerberos principal: A unique individual account known to the Key Distribution Center (KDC). Often a user, but it can be a service offering a resource on the network.

key: In cryptography, a generic term used to refer to cryptographic data that is used to initialize a cryptographic algorithm. Keys are also sometimes referred to as keying material.

Key Distribution Center (KDC): The Kerberos service that implements the authentication and ticket granting services specified in the Kerberos protocol. The service runs on computers selected by the administrator of the realm or domain; it is not present on every machine on the network. It must have access to an account database for the realm that it serves. KDCs are integrated into the domain controller role. It is a network service that supplies tickets to clients for use in authenticating to services.

little-endian: Multiple-byte values that are byte-ordered with the least significant byte stored in the memory location with the lowest address.

object identifier (OID): In the context of an object server, a 64-bit number that uniquely identifies an object.

objectGUID: The attribute on an Active Directory object whose value is a GUID that uniquely identifies the object. The GUID value of an object's objectGUID is assigned when the object was created and is immutable thereafter. The integrity of object references between NCs and of replication depends on the integrity of the objectGUID attribute. For a descrption of the general concept of an "object", see [MS-ADTS] section 1. For more detailed information see [MS-ADTS] section

pre-authentication: In Kerberos, a state in which a key distribution center (KDC) demands that the requestor in the Authentication Service (AS) exchange demonstrate knowledge of the key associated with the account. If the requestor cannot demonstrate this knowledge, the KDC will not issue a ticket-granting ticket (TGT) ([RFC4120] sections 5.2.7 and 7.5.2).

privilege attribute certificate (PAC): A Microsoft-specific authorization data present in the authorization data field of a ticket. The PAC contains several logical components, including group membership data for authorization, alternate credentials for non-Kerberos authentication protocols, and policy control information for supporting interactive logon.

read-only domain controller (RODC): A domain controller (DC) that does not accept originating updates. Additionally, an RODC does not perform outbound replication. An RODC cannot be the primary domain controller (PDC) for its domain.

realm: A collection of key distribution centers (KDCs) with a common set of principals, as described in [RFC4120] section 1.2.

RestrictedKrbHost services: The class of services that use SPNs with the serviceclass string equal to RestrictedKrbHost, whose service tickets use the computer account's key and share a session key. For information on the serviceclass string, see section

secret key: A symmetric encryption key shared by two entities, such as between a user and the domain controller (DC), with a long lifetime. A password is a common example of a secret key. When used in a context that implies Kerberos only, a principal's secret key.

security identifier (SID): An identifier for security principals that is used to identify an account or a group. Conceptually, the SID is composed of an account authority portion (typically a domain) and a smaller integer representing an identity relative to the account authority, termed the relative identifier (RID). The SID format is specified in [MS-DTYP] section 2.4.2; a string representation of SIDs is specified in [MS-DTYP] section 2.4.2 and [MS-AZOD] section

Security Support Provider Interface (SSPI): A Windows API that provides the means for connected applications to call one of several security providers to establish authenticated connections and to exchange data securely over those connections. It is equivalent to Generic Security Services (GSS)-API, and the two APIs are on-the-wire compatible.

service: A process or agent that is available on the network, offering resources or services for clients. Examples of services include file servers, web servers, and so on.

service principal name (SPN): (1) The name a client uses to identify a service for mutual authentication. (For more information, see [RFC1964] section 2.1.1.) An SPN consists of either two parts or three parts, each separated by a forward slash ('/'). The first part is the service class, the second part is the host name, and the third part (if present) is the service name. For example, "ldap/dc-01.fabrikam.com/fabrikam.com" is a three-part SPN where "ldap" is the service class name, "dc-01.fabrikam.com" is the host name, and "fabrikam.com" is the service name. See [SPNNAMES] for more information about SPN format and composing a unique SPN.

(2) The name a client uses to identify a service for mutual authentication. For more information, see [MS-ADTS] section 2.2.21 (Service Principal Name) and [RFC1964] section 2.1.1.

service ticket: A ticket for any service other than the ticket-granting service (TGS). A service ticket serves only to classify a ticket as not a ticket-granting ticket (TGT) or cross-realm TGT, as specified in [RFC4120].

session: In Kerberos, an active communication channel established through Kerberos that also has an associated cryptographic key, message counters, and other state.

session key: A relatively short-lived symmetric key (a cryptographic key negotiated by the client and the server based on a shared secret). A session key's lifespan is bounded by the session to which it is associated. A session key has to be strong enough to withstand cryptanalysis for the lifespan of the session.

SRV record: A type of information record in DNS that maps the name of a service to the DNS name of a server that offers that service. domain controllers (DCs) advertise their capabilities by publishing SRV records in DNS.

ticket: A record generated by the key distribution center (KDC) that helps a client authenticate to a service. It contains the client's identity, a unique cryptographic key for use with this ticket (the session key), a time stamp, and other information, all sealed using the service's secret key. It only serves to authenticate a client when presented along with a valid authenticator.

ticket-granting service (TGS): A service that issues tickets for admission to other services in its own domain or for admission to the ticket-granting service in another domain.

ticket-granting service (TGS) exchange: The Kerberos subprotocol in which the key distribution center (KDC) distributes a session key and a ticket for the service requested by the client, as specified in [RFC4120] section 3.3. This exchange is initiated when the client sends the KDC a KRB_TGS_REQ message.

ticket-granting ticket (TGT): A special type of ticket that can be used to obtain other tickets. The TGT is obtained after the initial authentication in the Authentication Service (AS) exchange; thereafter, users do not need to present their credentials, but can use the TGT to obtain subsequent tickets.

user principal name (UPN): A user account name (sometimes referred to as the user logon name) and a domain name that identifies the domain in which the user account is located. This is the standard usage for logging on to a Windows domain. The format is: someone@example.com (in the form of an email address). In Active Directory, the userPrincipalName attribute of the account object, as described in [MS-ADTS].

MAY, SHOULD, MUST, SHOULD NOT, MUST NOT: These terms (in all caps) are used as defined in [RFC2119]. All statements of optional behavior use either MAY, SHOULD, or SHOULD NOT.