itwbennett writes: When Jose Vildoza's father became the victime of ransomware, he launched his own investigation. Diving into CryptoDefense's code, he found its developers had made a crucial mistake: CryptoDefense used Microsoft's Data Protection API (application programming interface), a tool in the Windows operating system to encrypt a user's data, which stored a copy of the encryption keys on the affected computer. Vildoza and researcher, Fabian Wosar of the Austrian security company Emsisoft, collaborated on a utility called the Emsisoft Decrypter that could recover the encrypted keys. In mid-March Vildoza had launched a blog chronicling his investigation, purposely not revealing the mistake CryptoDefense's authors had made. But Symantec then published a blog post on March 31 detailing the error.