Legally distributed e-books are protected by copyright using various technological solutions referred to as DRM (Digital Rights Management). DRM systems are used to encrypt e-book files and restrict such files to certain devices. DRM-protected e-books cannot be copied between devices. DRM implementations vary between e-reader device manufacturers.
Adobe DRM is the most commonly used DRM implementation. User are given special Adobe ID code after installing Adobe Digital Editions Software application. This ID is then used to encrypt e-books in user’s collection and is necessary to open those e-books. The systems is sometimes referred to as ADE (Adobe Digital Editions) and is mostly compatible with PDF and EPUB formats. It uses 256-bit AES encryption.
Amazon DRM is used by Kindle readers. This DRM implementation is only compatible with native Kindle e-book format (AZW). Kindle do not support EPUB format. Amazon DRM uses the proprietary Whispernet protocol for authenticating users. Encrypted AZW files cannot be access on any other devices. Amazon DRM uses 128-bit PC1 encryption algorithm.
Popular DRM standard adopted by many web book vendors. FileOpen DRM is managed via a dedicated plugin for Adobe Acrobat Reader application, which is not supported on many e-readers.
Proprietary DRM system developed by Kolporter company and supported only on eClicto e-readers.
DRM system similar to that of Amazon. Mobipocket is an online DRM service that can be used to add devices on which given e-books will be accessed. Mostly used for MOBI e-book files.
Sony uses its own DRM protection solution implemented in LRX e-book files. LRX files can only be opened on SONY e-reader devices or using dedicated desktop software.