Properly wiping a hard drive ?

[Linuxguy123]

On Sat, 2010-10-09 at 02:27 -0600, Linuxguy123 wrote:

> 
> >From man hdparm:
> 
>  --security-erase PWD
>               Erase  (locked)  drive,  using password PWD (DANGEROUS).
> Password is given as an ASCII string and is padded
>               with NULs to reach 32 bytes.  Use the special password
> NULL to represent an empty password.  The  applicable
>               drive  password is selected with the --user-master switch.
> No other flags are permitted on the command line
>               with this one.  THIS FEATURE IS EXPERIMENTAL AND NOT WELL
> TESTED. USE AT YOUR OWN RISK.
> 
> 
> In actual use:
> 
> # hdparm --security-erase NULL /dev/sdd
> security_password=""
> 
> /dev/sdd:
>  Issuing SECURITY_ERASE command, password="", user=master
> ERASE_PREPARE: Invalid exchange
> 
> Why ????

I have this drive connected via a USB adapter.   Would that cause this
problem ?