To use SHA256 or SHA512 for encrypting passwords in libuser, configure the
following variables the [defaults] section of libuser.conf:

crypt_style
	The algorithm to use for password encryption when creating new
 	passwords.  The current algorithm may be retained when changing a
 	password of an existing user, depending on the application.

	Possible values are des, md5, blowfish (unimplemented), sha256 and
	sha512, all case-insensitive.  Unrecognized values are treated as des.
	Default value is des.

hash_rounds_min, hash_rounds_max
	These variables specify an inclusive range of hash rounds used when
	crypt_style is sha256 or sha512.  A number of hash rounds is chosen
	from this interval randomly.  A larger number of rounds makes password
	checking, and brute-force attempts to guess the password by reversing
	the hash, more CPU-intensive.  The number of rounds is restricted to
	the interval [1000, 999999999].

	If only one of the above variables is specified, the number of rounds
	used is specified by the other variable.  If neither variable is
	specified, the number of rounds is chosen by libc.
