Password mask is a template defining allowed characters for each position of the password
candidates. The mask has the form of a string containing one or more symbols. A password mask m
of length n is defined as:

m = s1 s2 … sn

Obviously, the candidate passwords has the same length n as the mask. The meaning of symbol in the mask is:

symbol description characters in set
?l lowercase Latin letters abcdefghijklmnopqrstuvwxyz
?d digits 0123456789
?s special characters (space)!”#$%&’()*+,-./ :;<=>?@[\]^_‘{|}~
?h hexadecimal digits with small letters 0123456789abcdef
?H hexadecimal digits with big letters 0123456789ABCDEF
?a all standard ASCII characters: ?l, ?u, ?d, ?s
?b binary – all bytes with values between 0x00 and 0xFF
?1 user-defined character set no. 1
?2 user-defined character set no. 2
?3 user-defined character set no. 3
?4 user-defined character set no. 4