Encryption for RADIUS key?

On the N-Series switches, the radius key is, by default, shown in plaintext in the configuration file.

There's an option via CLI to specify an encrypted value, but it says the parameter length should be exactly 256 characters. The CLI documentation doesn't specify any further about the encryption type or how to pre-encrypt the password.

I tried "SHA256-ing" my key but this only outputs 64 hex (256 bits). When it tells me 256 characters, I'm assuming that this means 256 hex (i.e. 1024 bits)?  I don't know how to generate this value from my key... any guidance?

Thanks!