I wrote Decrypt as a tool to unlock the poorly locked WordPerfect 5.1 (for DOS) files that I encountered at my law firm when people left the firm. It was free, open source code with a detailed explanation of the widely published algorithm and what WordPerfect could do to correct the problem (that they did in 6.0). At the time, it was the first free program to do this particular task. It was part of a set of free WordPerfect macros that were widely used at law clinics and legal aid societies in the late 1980's and early 1990's.
decrypt.exe