Most ransomware variants use asymmetric encryption (AES + RSA). Without the private key, you cannot mathematically reverse the encryption. This tool does not try.

But physically, on a spinning disk or flash storage, “writing back” doesn’t always overwrite the exact same physical sectors. Sometimes the OS writes to a new location and marks the old sectors as “deleted” (but not erased).

Modern ransomware (post-2020) often uses the NtSetInformationFile with FileDispositionInfo to bypass the recycle bin. Some even call FSCTL_SET_ZERO_DATA to zero out clusters. The restore utility cannot recover what has been physically overwritten. Most people do this wrong. They run the tool on the infected system after the ransomware has been cleaned. That’s too late. Every second the system runs, the OS writes logs, updates, and temp files—overwriting the very sectors you want to carve.

Keep a copy of restore.exe on a USB drive before you get infected. If you wait until after, downloading it onto the compromised machine might overwrite the very sectors you need to recover.

TL;DR: The Kaspersky Restore Utility is not a backup tool. It is a forensic-grade, signature-agnostic file-carving engine designed to resurrect data from drives that ransomware has deliberately tried to destroy. If you think your encrypted files are gone forever, this is your last line of defense.