the same entropy encoder employed by JPEG 2000. Patents Patents for JBIG2 are owned by IBM and Mitsubishi. Free licenses should be available after a request. JBIG and JBIG2 patents are not the same. Disadvantages When used in lossy mode, JBIG2 compression can potentially alter text in a way that's not discernible as corruption. This is in contrast to some other algorithms, which simply degrade into a blur, making the compression artifacts obvious. Since JBIG2 tries to match up similar-looking symbols, the numbers "6" and "8" may get replaced, for example. In 2013, various substitutions (including replacing "6" with "8") were reported to happen on many Xerox Workcentre photocopier and printer machines. Numbers printed on scanned (but not OCR-ed) documents had potentially been altered. This has been demonstrated on construction blueprints and some tables of numbers; the potential impact of such substitution errors in documents such as medical prescriptions was briefly mentioned. German computer scientist David Kriesel and Xerox were investigating this. Xerox subsequently acknowledged that this was a long-standing software defect, and their initial statements in suggesting that only non-factory settings could introduce the substitution were incorrect. Patches that comprehensively address the problem were published later in August, but no attempt has been made to recall or mandate updates to the affected devices – which was acknowledged to affect more than a dozen product families. Documents previously scanned continue to potentially contain errors making their veracity difficult to substantiate. Following publicity about the potential for errors authorities in some countries made statements to prevent the use of JBIG2. In Germany the Federal Office for Information Security has issued a technical guideline that says the JBIG2 encoding "MUST NOT be used" for "replacement scanning". In Switzerland the Coordination Office for the Permanent Archiving of Electronic Documents (Koordinationsstelle für die dauerhafte Archivierung elektronischer Unterlagen) has recommended against the use of JBIG2 when creating PDF documents. Exploit A vulnerability in the Xpdf implementation of JBIG2, re-used in Apple's iOS phone operating software, was used by the Pegasus spyware to implement a zero-click attack on iPhones by constructing an emulated computer architecture inside a JBIG2 stream. Apple fixed this "FORCEDENTRY" vulnerability in iOS 14.8 in September 2021. References External links T.88: Lossy/lossless coding of bi-level images Lossless compression algorithms Lossy compression algorithms Graphics file formats Image compression 2