I'm working on a rollback method that will allow users to recover corrupt files if a power loss occurs during encryption. As you can imagine ensuring that Envelope is secure and adding a rollback method is quite difficult. When files are encrypted Envelope will make use of temporary files to minimise the size of the program in memory. These temporary files are securely deleted after encryption has finished or when envelope is started (if files existed from previous jobs).
If Envelope detects that these files exist it will prompt the user to either delete them using the secure deletion method or to attempt to recover them. The recovery process will work in the opposite way to the compression, encryption and noise insertion methods. Envelope will index the key ID for each file when processing the file therefore if the computer does fail Envelope will be able to recover the file using the original keystore without storing any sensitive data on the computer.
Rollback may not be available in the first release of Envelope however I do hope to add it in due course.