These are commonly used subsets of the alphabet that the FFX
mode natively supports. In the algorithm, the alphabet is
selected using the "radix". Therefore each corresponds to a
particular radix.
Values:
FFX_COMMON_NATIVE_ALPHABET_UNSPECIFIED (0):
Unused.
NUMERIC (1):
[0-9] (radix of 10)
HEXADECIMAL (2):
[0-9A-F] (radix of 16)
UPPER_CASE_ALPHA_NUMERIC (3):
[0-9A-Z] (radix of 36)
ALPHA_NUMERIC (4):
[0-9A-Za-z] (radix of 62)