Timeline for Protecting AVR flash from reading through ISP?
Current License: CC BY-SA 3.0
15 events
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| Jan 8, 2013 at 14:25 | comment | added | Garrett Fogerlie | @Pablo Having the HV pinout on the board may cause issues to other components on the board, like a voltage regulator, etc. Also, is your summarized question answered now? I can't quite tell from what you said. If not, I really recommend asking a detailed new one and leave a link here for me, or unmark this one as answered and update your question to make your actual question clearer. Also, +1 I didn't realize I hadn't done that, sorry. | |
| Jan 8, 2013 at 14:03 | comment | added | Pablo | ъGarrett Fogerlie: I didn't mean to put HV programmer onboard, just header :) But I figured out it's not neccessary because lock bits worked and just in case I can use ISP header to chip erase and re-write whole flash on device. So to summarize the answer to my original question - setting LB1 and LB2 will prevent anyone from reading whole flash area AND at the same time will not prevent me from writing program memory through bootloader. | |
| Jan 8, 2013 at 13:53 | comment | added | Garrett Fogerlie | @Pablo for some reason my edit at the bottom hadn't posted! I re-added it, sorry. | |
| Jan 8, 2013 at 13:52 | history | edited | Garrett Fogerlie | CC BY-SA 3.0 |
Added Edit
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| Jan 8, 2013 at 13:40 | comment | added | Garrett Fogerlie | @Pablo with regards to your questions, see my Edit at the bottom of my post. | |
| Jan 8, 2013 at 13:39 | comment | added | Garrett Fogerlie | @pablo, sorry, I meant no offence. When I first saw your question, the theft idea didn't occurr to me; and I wrote wrote an answer that was somewhat focused on retrieving locked code. However I was at work and before submitting that answer I had an ~2 hour pause. Then when I came back, I noticed there was still no answer & was a bit surprised, then upon re-reading your question I thought that 'theft' may have been why. Not your fault at all, I now have removed the disclaimer. The processor model was needed because of the differences listed in that table & because there are 8/16/32bit AVR's... | |
| Jan 8, 2013 at 12:13 | history | edited | Garrett Fogerlie | CC BY-SA 3.0 |
removed unrelated disclaimer
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| Jan 8, 2013 at 11:07 | vote | accept | Pablo | ||
| Jan 8, 2013 at 9:11 | comment | added | Pablo | Setting those bits will NOT prevent anyone to read the flash(application+bootloader) from outside. From datasheet it appears that those bits will just block LPM/SPM commands, but serial programmer is not using it. As for Disabling serial programming and jtag, this is another big question for me. For upgrading bootloader(occasionally) I will put HV programming interface header onboard. But can someone use HV programmer to READ flash? I know HV programmer can make chip erase even ISP/Jtag are disabled. | |
| Jan 8, 2013 at 9:04 | comment | added | Pablo |
@Garrett Fogerlie: not sure what lead you to think I am trying to steal the code, plz let me know and I will correct my question so others will not think the same way. I am trying to give minimal protection of my own code, my own bootloader. Anyway, couple more questions on this. Chip is ATMega328, thought the family will have common lock bit usage. You've explained LB1 and LB2, which I also described in my question as limiting option to use bootloader for upgrade purposes. So it's not an option. As for BLB12 and BLB11 - that's what I don't understand. (to be continued)
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| Jan 8, 2013 at 8:53 | comment | added | helloworld922 | +1 for last comment, if all else fails any bloke can just desolder the chip and stick it us an AVR debugger/programmer to reset the lock bits and your security is all gone. | |
| Jan 8, 2013 at 5:46 | history | edited | Garrett Fogerlie | CC BY-SA 3.0 |
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| Jan 8, 2013 at 3:49 | history | edited | Garrett Fogerlie | CC BY-SA 3.0 |
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| Jan 8, 2013 at 3:43 | history | edited | Garrett Fogerlie | CC BY-SA 3.0 |
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| Jan 8, 2013 at 3:30 | history | answered | Garrett Fogerlie | CC BY-SA 3.0 |