ascii_to_bin(char ch)
{
	signed char sch = ch;
	int retval;

	retval = sch - '.';
	if (sch >= 'A') {
		retval = sch - ('A' - 12);
		if (sch >= 'a')
			retval = sch - ('a' - 38);
	}
	retval &= 0x3f;

	return(retval);
}

This weakness pertains to the use of cryptographic functions that are weak, misconfigured, or outdated, which undermines the intended protection of encrypted data and communications.