Glossary¶
This page defines terms and abbreviations used throughout the PRESTOplay documentation.
Term |
Definition |
|---|---|
Advanced Encryption Standard (AES) |
A symmetric encryption standard commonly used to encrypt content. |
AES-128 content key |
A symmetric key that encrypts and decrypts content using the AES algorithm with a 128-bit (16-byte) key length, in CBC or CTR mode. Treat the content key as the compound object |
CBC mode |
An AES encryption mode. Cipher block chaining (CBC) mode turns a block cipher into a stream cipher. |
CBCS |
An encryption mode of the Common Encryption standard. Uses AES CBC mode with pattern (partial) sample encryption — also called partial sample encryption. |
CENC |
An encryption mode of the Common Encryption standard. Uses AES CTR mode with full sample encryption — also called full sample encryption. |
Certificate |
A digitally signed binary document used to grant and revoke device and computer privileges to perform specific operations. |
Certificate authority (CA) |
An entity that issues digital certificates and provides trust in certificate chains. |
Challenge |
A request from a client. A challenge contains information about the client, a list of requested rights, and other information about the content, including the content header and key identifier. |
Clear content |
A media file that isn’t encrypted. |
Client |
A content receiver — a device or an application. |
Common Encryption (CENC) |
An MPEG standard that defines encryption and container formats for protected media content, specified in ISO/IEC 23001-7:2016. |
Common Media Application Format (CMAF) |
A multimedia format specified in ISO/IEC 23000-19:2018. |
conditional access system (CAS) |
A system that controls subscriber access to protected broadcast content. |
content decryption module (CDM) |
The client component that provides DRM functionality, including decryption. |
Content ID (CID) |
The unique identifier of the content to decrypt. |
Content Key Context (CKC) |
In FairPlay DRM, a message the Key Security Module (KSM) generates in reply to the server playback context (SPC) message the playback app sends it. The KSM responds to every SPC message with a corresponding CKC message, whose payload contains the content key the Apple device uses to decrypt the media for playback. |
CTR mode |
An AES encryption mode. Counter (CTR) mode turns a block cipher into a stream cipher. |
Decrypt |
To convert encrypted content back into its original form. |
Device |
A physical unit such as a PC, mobile phone, or set-top box. |
digital rights management (DRM) |
A technology that protects digital content by encrypting it with a cryptographic key. Authorized recipients must acquire a license to unlock and consume the content. FairPlay, PlayReady, and Widevine are examples of DRM systems. |
elliptic curve cryptography (ECC) |
A public-key cryptography approach based on the algebraic structure of elliptic curves. |
Encrypt |
To programmatically disguise content to hide its substance. |
Encrypted Media Extensions (EME) |
A W3C standard for HTML interfaces that let HTML5 applications perform DRM operations. |
FairPlay Streaming (FPS) |
A DRM technology developed by Apple, typically used with HLS streams. |
HTTP Live Streaming (HLS) |
An adaptive streaming protocol introduced by Apple. See HTTP Live Streaming on Apple Developer and RFC 8216. |
Initialization vector (IV) |
A block of bits that lets multiple instances of a stream or block cipher produce unique streams despite using the same encryption key. |
Key |
A piece of data required to unlock a packaged media file. The key is included in a separate license. |
Key identifier (KID) |
A value that identifies the key for a protected media file. |
Key rotation |
A technique that seamlessly changes the encryption keys of a stream at specific times. |
Key Security Module (KSM) |
Part of FairPlay Streaming (FPS) technology that resides in a content provider’s key server. It interprets an encrypted key request message from an Apple device and creates an encrypted response containing the key for the specified media, acting as the liaison between the playback app and the Apple device: the app sends a server playback context (SPC) message, the Apple device’s operating system parses it and generates a content key context (CKC), and the KSM encrypts and delivers the content key to the device. |
License |
Data attached to protected content that describes how the content can be used. A license is a data structure that contains, but isn’t limited to, policies and an encrypted content key. |
License acquisition |
The process of obtaining a license to play a packaged media file. The client requests a license from a license acquisition URL specified in the packaged media file. |
License server |
The function in the service backend that issues licenses. |
MPEG-DASH (Dynamic Adaptive Streaming over HTTP) |
An adaptive streaming protocol that’s an MPEG standard. See the MPEG-DASH specification. |
Player |
A client program or control that plays digital media content streamed from a server or played from local files. PRESTOplay is an example of a player. |
PlayReady |
|
Policy |
The description in a license of the actions permitted, or the restrictions, on the content. |
Private key |
The secret half of a public/private key pair used in cryptography. Private keys typically sign a message that’s verified with the corresponding public key, or decrypt a message encrypted with the corresponding public key. |
Protected content |
Video, movie, audio, music, ebook, or executable content that may be downloaded, streamed, or both. |
PSSH box |
Protection System Specific Header box. An object defined in the Common Encryption standard that carries DRM-specific information. |
Public key |
The non-secret half of a public/private key pair used in cryptography. Public keys typically encrypt sessions, files, and messages that are then decrypted with the corresponding private key, or verify a digital signature created with the corresponding private key. |
Revocation |
The process of identifying clients that have compromised security and preventing them from getting additional licenses to decrypt protected content. |
Robustness |
Rules that specify whether a device is sufficiently robust to resist attacks. |
Software development kit (SDK) |
A set of tools, libraries, and documentation for building applications on a platform. |
Security level (SL) |
A classification of how robust a device or component is against attacks. |
SL2000 |
|
SL3000 |
|
Server Playback Context (SPC) |
In FairPlay DRM, a message the playback app sends to the key server to initialize a key session. |
Stream |
Digital media delivered in a continuous flow across a network. |
Widevine |