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Per Westermark
07/13/12 21:29
Read: 579 times

#187928 - Checksum
Responding to: ???'s previous message
They probably had a checksum in the EEPROM too.

There aren't much need for extra security with the EEPROM since anyone who can get access to the electronics of a safe don't need to bother with any PIN code. The only open issue is what to do if you get a checksum error - in that case, the EEPROM cells could potentially even represent a PIN code that can't be entered with four normal digits.

Another thing is that anything with just a 4-digit PIN has a rather low security class, so there really isn't a need to try too hard at security. But you should have a counter for number of PIN-code attempts, and after 3 errors refuse to process PIN codes for a long time - at least 10 minutes. And there must be no difference in behavior of the software until that fourth digit has been pressed.

List of 13 messages in thread
Password in EEPROM      Arif Deshmukh      07/13/12 17:29      
   Checksum      Per Westermark      07/13/12 21:29      
      8-digit code      Per Westermark      07/13/12 21:36      
         Master Code      Arif Deshmukh      07/13/12 22:35      
            So what does the requirements spec say?      Per Westermark      07/13/12 22:47      
            master codes ....      Erik Malund      07/14/12 01:12      
               This is a low-security lock - or no measly 4-digit PIN      Per Westermark      07/14/12 01:18      
                  language      Erik Malund      07/14/12 08:48      
                     just a thought      Erik Malund      07/14/12 09:09      
                        Never give access when locked      Per Westermark      07/14/12 10:14      
                     PIN + PUK      Per Westermark      07/14/12 10:11      
   The eeprom doesnt hold the password      Jez Smith      07/14/12 19:57      
      High/low security        Per Westermark      07/14/12 23:10      

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