RAR password recovery. Why so slow? And why is the “Current speed” incorrect?
This is a peculiarity of these archives.
The RAR password recovery scheme is different from others and allows miscalculations while estimating the speed of password recovery tools (AccentRPR and our competitors). This happens due to the structure of a particular RAR archive.
"Current speed" is the “peak” speed. For RAR archives, it can be incorrect if the program is trying to open a large archive without header encryption (it gets easier with an encrypted header – the entire archive doesn’t have to be unpacked).
Recovery of a RAR password consists of two stages:
1. "Passwords to keys". Calculating the encryption key from the password being checked. Transformation itself is fairly fast (its speed is shown as "current speed").
2. "Validate keys". To check a password, you need to completely unpack the entire archive and compare its contents with control values. The bigger the RAR archive, the more time is needed for unpacking it and the lower the actual password recovery speed is (displayed as “Average speed” and used for calculating the “Estimated time” parameter).
Therefore, the size and structure of a particular RAR archive fully defines the speed of password recovery. The speed can be completely different for another RAR archive.
NOTE: All of this relates to RAR archives of the RAR3 format. Newer RAR5 archives do not have such flaws and the speed of password recovery is always stable.