The PDF Association is proud to present the first PDF 2.0 example files made available to the public. Created and donated to the PDF Association by Datalogics, this initial set of PDF 2.0 examples were crafted by hand and intentionally made simple in construction to serve as teaching tools for learning PDF file structure and syntax.PDF 2.0: The worldwide standard for electronic documents has evolved
The Portable Document Format is perhaps the most common example of a de facto standard, so much so that Wikipedia features PDF on its “de facto standards” page. From Ethernet and 802.11 to HTTP and CSS, the modern computing stack consists of hundreds o …PDF 2.0 interops help vendors
The PDF 2.0 interop workshops included many vendors with products for creating, editing and processing PDF files. They came together in Boston, Massachusetts for a couple of days to test their own software against 3rd party files.PDF Days Europe underscores the importance of PDF as a key component of business processes
2017 marks a record number of attendees / Experts shared fully-grounded wisdom on PDF standards across the two-day event Berlin. With over 200 attendees, this year’s PDF Days Europe in Berlin was a significant success with the largest attendance of any …Slides and video recordings of the PDF Days Europe 2017
About 35 informative sessions across a wide range of topics, including the next-generation PDF project. Within the video frames you can use the red “play” button to get a short impression of the talk or can enjoy the high resolution version by clicking …
As we reported yesterday, those in the crypto world are well-aware that Google and others have proven that SHA-1, the venerable cryptographic hash function standard, is dead. The consequences, however, are yet to be determined. Somewhere, it is safe to assume, between very very bad and catastrophic.
Among many other potential points of disruption, this recently announced SHA-1 collision attack, as PC World reported, can break code repositories that use the Subversion (SVN) revision control system. To prove the point, it seems, the WebKit browser engine repository became corrupted after someone committed two different PDF files with the same SHA-1 hash to it.
The team responsible for uncovering this vulnerability state on their website, SHAttered.io:
The could have used a variety of different file-types to make this point, but PDF files, of course, contain more information and benefit from more trust.
The PDF specification up through ISO 32000-1 (PDF 1.7) allowed use of SHA-1 for a variety of hashing functions. However, in PDF 2.0, SHA-1 is formally deprecated for use in digital signatures. This means that a PDF 2.0 writer should not use SHA-1 to make a message digest, and a PDF 2.0 reader may reject signatures that still use SHA-1.
Does this mean that PDFs that were signed using the SHA-1 algorithm in the past suddenly become invalid? In principle, it is now proven that the contents of such a PDF can be changed without invalidating the signature. However, the problem only exists in situations where companies didn’t upgrade their document systems to the latest standards.
“For those who are stuck with SHA-1 in their existing repositories of PDF documents, PDF 2.0’s new Document Security Store (DSS) including Validation-Related Information (VRI), as well as a document time-stamp (DTS) signature,” says iText founder Bruno Lowagie. “The document time-stamp signature (subtype ETSI.RFC3161) is an additional signature that should use a more recent hashing algorithm to create the message digest. The procedure of adding a DSS and a document time-stamp should be repeated before the certificate of the last signature that was added expires, or when there are indications that the algorithms that were used, whether the cryptographic hash function or the encryption algorithm, could be jeopardized,” Lowagie said.
PDF developers can test their software – and its response to SHA-1 – in the PDF 2.0 context long before it gets to customers. In January, the PDF Association announced two PDF 2.0 interop workshop events in the UK, and USA, to help PDF developers test their PDF 2.0 files or implementations against others.
The death of SHA-1 makes an excellent case for testing new encryption models and circumstances. Billions of PDF files worldwide rely on secure digital signatures, encryption and other features that use hashing to disambiguate documents. PDF 2.0 is an excellent opportunity to negate this risk for PDF users.