Portable Blockchain Format


In 1993 Adobe Systems published version one of the Portable Document Format specification, the PDF file that comprises a set of objects. A key design consideration was to enable the file to be created with a single pass. The specification included an incremental update to allow files to be updated without going back and deleting previous objects, it was also designed to be extensible. Now at version 2.0 the PDF Specification is an ISO specification with a rich set of features included support for digital signatures and collections of documents and data.

In 2009 David Siegal in his book Pull describes “The Personal Data Locker” and how it might be used to enable an individual to control and share their information with other parties. Although published after Satoshi Nakamoto’s 2008 paper it makes no reference to distributed ledgers or any other implementation technology.


The Portable Blockchain Format involves embedding a blockchain within a PDF document collection it will be possible for an individual to establish the chain of evidence for a claim that an individual is making. For example, consider the classic case of proving that you are over a particular age. A number of zero knowledge proof algorithms exist to enable this but they all rely on someone originally accepting that a copy of the birth certificate is valid. A copy of the birth certification can be scanned into a PDF document and this document signed by a trusted authority. This document is then encrypted and included in a PDF collection, the signature recorded in the internal blockchain and then the algorithm parameters can be published using public key cryptography.


A personal data locker implemented using the Portable Blockchain Format demands that five criteria must be met:

  • Allow a consumer to populate their data locker
  • Allow the consumer to selectively share information from the data locker
  • Protect the consumer from their own errors
  • Protect organisations from consumer fraud
  • Enable a consumer’s will to be executed after they die
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