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Developer(s)EZB Systems
Initial releaseApril 20, 2002
Stable release
9.76 / 7 August 2021; 2 years ago (2021-08-07)[1]
Operating systemMicrosoft Windows
PlatformIA-32 and x86-64
TypeOptical disc authoring software and virtual drive

UltraISO is a crippleware application for Microsoft Windows for creating, modifying and converting ISO image files used for optical disc authoring, currently being produced by EZB Systems.

Initially UltraISO was shareware however since 2006 it has turned into commercial software.[2] The 'Free Trial' version is limited to ISO images of 300 MB or less, effectively making it Crippleware.[3]

ISZ format[edit]

UltraISO uses a proprietary format known as ISZ. The format is advertised as "ISO Zipped", even though it is not a simple zip archive. The format uses zlib or bzip2 to compress the data, and may use AES-128,192 or 256 encryption in the CBC mode[4] (note that this provides no integrity protection and is vulnerable to the padding oracle attack[5]). The file format specification is available publicly on EZB Systems's website.[4] The format is now supported by third party applications such as Daemon Tools, Alcohol 120% and CDemu.

See also[edit]


  1. ^ "UltraISO Revision History".
  2. ^ "Order UltraISO - EZB Systems, Inc".
  3. ^ "ISO Images Editing Made Easier". 27 June 2006.
  4. ^ a b "ISZ File Format Specification". EZB Systems. 2006-07-03. Retrieved 2008-09-24.
  5. ^ "CBC decryption vulnerability". Microsoft docs. Retrieved 29 Jan 2022.

External links[edit]