Since this is an unofficial "GSM" repair tool, there is no single official website. It is typically found on: GSM developer forums (such as GSM-Forum or Martview-Forum).
: The tool usually requires the device to be in "Purple Mode" (a diagnostic state) to modify the SysCfg data where the serial number is stored. Kratius SN Changer V1.0 [ 7 to X ] Free Download
Dedicated YouTube tutorial descriptions from technical repair channels. Niche software repositories for iOS bypass tools. Since this is an unofficial "GSM" repair tool,
: Using such tools to bypass security features may violate terms of service or local laws regarding digital security. Where to Find It Kratius SN Changer V1.0 [ 7 to X ] Free Download