generates cryptographic keys, registers with the
tarsnap server, and writes a key file for use with
parameters are all required.
option is specified, the user will be prompted to enter a passphrase (twice)
to be used to encrypt the key file.
option is specified, a maximum of
bytes of RAM will be used in the scrypt key derivation function to
encrypt the key file; it may be necessary to set this option if a key
file is being generated on a system with far more RAM than the system
on which the key file will be used.
option is specified, a maximum of approximately
seconds will be used in the scrypt key derivation function to
encrypt the key file.