Here is the helpful guide on how to download and install it safely.
The utility is typically not available on a public download page but is hosted within secure login portals for registered users. Primary Source : Access the login portal of the Online SAM/PAAM application. Once logged in, look for the option: nsdlssusersetup200 download link
NSDL e-Services Portal: Most user-facing utilities are listed on the SPEED-e Downloads page, which includes signature verification and offline file signing tools. Here is the helpful guide on how to