Preserving control characters (HTML->XHTML)

Hello,

I am using TidyLib to convert HTML to XHTML.

The original HTML contains control-H (0x08) characters. These characters are
used for auth purposes.

I have TidyLib configured as:

tidyOptSetBool(tdoc, TidyXhtmlOut, yes);
tidyOptSetBool(tdoc, TidyForceOutput, yes);
tidyOptSetValue(tdoc, TidyCharEncoding, "raw");

When the HTML is converted, the control-H characters are lost. Is there any
option I can use to preserve
these characters? Maybe even something that would set them to 

Thanks,
-- Jason