Technically speaking, Office 97 apps made use of RC4 for encryption and MD5 for hashing. While native US versions of Microsoft Office could be configured to use somewhat stronger encryption, the setting was rarely enabled because of compatibility concerns.

The artificial vulnerability existed due to US export restrictions. Microsoft Office 97 apps were released with deliberately weak encryption, which was carried over to Office 2000. All passwords for all versions of Word and Excel up to and including Office 95 could be recovered instantly brute-force attacks were not required. Even back in the day the strength of this algorithm was more of an obfuscation rather than encryption. These versions of Microsoft Office apps employed a weak encryption algorithm based on XOR operation. In this article we’ll explain the differences between the many types of protection one can use in the different versions of Microsoft Office tools, and explore what it takes to break such protection. While certain types of passwords (even in the latest versions of Office) can be broken in an instant, some passwords can be extremely tough to crack. Since Word 2.0 released in 1991, Microsoft has been using encryption to help users protect their content. With its backward file format compatibility, Microsoft Office has become a de-facto standard for documents interchange. With more than 1.2 billion users of the desktop Office suite and over 60 million users of Office 365 cloud service, Microsoft Office files are undoubtedly the most popular tools on the market. During the past thirty years, Microsoft Office has evolved from a simple text editor to a powerful combination of desktop apps and cloud services.

The first Microsoft Office product was announced back in 1988.

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