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I am trying to understand how encrypted ("password protected") Office 2007 documents are bundled (specifically, Excel documents). I am experimenting with a known, password protected spread sheet.
When I unzip the XLSX file, I encounter three entries:
How is the EncryptedPackage file encrypted (which cipher, which key derivation function, etc...)?
I have tried referencing the documentation, but I haven't had much success.
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Office Open XML (also informally known as OOXML) is a zipped, XML-based file format developed by Microsoft for representing spreadsheets, charts, presentations and word processing documents. Ecma International standardized the initial version as ECMA-376. ISO and IEC standardized later versions as ISO/IEC 29500.
docx file) is protected with a password for reading, it is encrypted. The encrypted OOXML file is stored inside a Compound File Binary Format file, or what I like to call an OLE file. This is the “old” MS Office file format (like . doc), the default file format used before MS Office 2007.
#1) Open Windows Explorer and browse to the location where the XML file is located. We have browsed to the location of our XML file MySampleXML as seen below. #2) Now right-click over the file and select Open With to choose Notepad or Microsoft Office Word from the list of options available to open the XML file.
OpenXML is also known as OOXML and it fully XML-based format for office documents, including word processing documents, spreadsheets, presentations, as well as charts, diagrams, shapes, and other graphical material.
File encryption is not part of the OpenXML ECMA/ISO specifications. It's a vendor-specific standard on top of that. For the specification please check out
[MS-OFFCRYPTO]: Office Document Cryptography Structure Specification
Encrypted OpenXML documents are not stored as an OPC zip package but as an encrypted OPC package inside a compound OLE document.
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