Lpc2000

Jaya,

I am truely sorry but I do not understand your point. A parallel 
programmer will not be able to read or program a secured device. A 
microcontroller that executes an external program can not be secured 
because the external code can always be compromised. Booting from 
external is not possible once the device is secured and programmed 
to boot internally.

Did I miss something?  Oh yes, you, the user is always able 
to "undo" your security while running IAP but how would a "spy" be 
ever able to run IAP (In application programming). The devices you 
mentioned also leave the option to reenable JTAG in your program, 
again, chicken and egg, as the spy will not be able to alter your 
program how can he enable JTAG. 

Philips Apps 


--- In lpc2000@yahoogroups.com, "jayasooriah" <jayasooriah@y...> 
wrote:
>
> Was Philips misleading us about Code Read Protection?
> 
> The preliminary user manual for LPC2119/2129/2194/2292/2294 dated 
2004
> May 03 in the section on CRP states:
> 
> > When the code read protection is enabled the JTAG debug
> > port, external memory boot and the following ISP commands
> > are disabled:
> >
> > • Read Memory
> > • Write to RAM
> > • Go
> > • Copy RAM to Flash
> >
> > The ISP commands mentioned above terminate with return
> > code CODE_READ_PROTECTION_ENABLED.
> >
> > The ISP erase command only allows erasure of all user
> > sectors when the code read protection is enabled.
> 
> Philips stated (by way of poster dated Sat Dec 17, 2005  11:52 AM)
> that the purpose of CRP as:
> 
> > Code Read Protection (CRP) was implemented with intention
> > to protect on-chip Flash content from preying eyes.
> 
> It appears that Philips made these claims while it knew that CRP 
can
> be defeated by other methods, including parallel programming or
> booting from external memory.
> 
> 1/  LPC parts without external memory interface support parallel
> programming.  This method can be used to read and write on-chip 
flash.
> 
> 2/  On LPC parts with external memory, it is possible to force the
> part to boot on external memory.  Code in external memory can read 
and
> write on-chip flash.
> 
> If the above claims are not true, it would be a simple matter for
> Philips to say so.  The fact that Philips has chosen to go quiet on
> this issue seems to suggest the claims are indeed true.
> 
> If this is the case, then clearly Philips has intentionally misled 
us.
> 
> Comments anyone?
> 
> Jaya
>