public static String generateIdentifier(int minBits) {
        return generateIdentifier(minBits, true);
    }
Generates a unique and unpredictable identifier having at least the
given number of bits of entropy. The resulting identifier may have more
than the number of bits required. The identifier may contain characters
that differ only in case.

@param minBits
    The number of bits of entropy that the identifier should contain.

@return
    A unique and unpredictable identifier with at least the given number
    of bits of entropy.
guacamole-ext/src/main/java/org/apache/guacamole/net/auth/IdentifierGenerator.java