how changing master key or other keys can provide security ?how used session key to keep the further communication between DESFire and reader? -


i working on ticket electronik tickets desfire cards.

i want communications safe . trying change picc key . before changing desfire master key authenticate master key necessary.

in desfire sheet authenticate @ page 31 described:

"this procedure not confirms both entities can trust each other generates session key can used keep further communication path secure. name “session key” implicitly indicates, each time new authentication procedure completed new key further cryptographic operations obtained."

i want know how changing master key or other keys can provide security ?i means need changing keys or not? , how used session key keep further communication between desfire , reader?

i'm not sure, whether points below answer question, consider not clear , further blurred added comments.

  • the default key known users of evaluation kit - therefore surely want change value known you.

  • any cryptographic algorithm deserving name unfeasible crack brute force.

  • any attack surely try documented default value used patterns "00 00...", "ff ff..", "01 02 03..". if attack succeeds here, have lost , transportation provider have severe problems since easy create new tickets.

  • a session key provides security against replay attacks (in session have value, not cirumventable outside world) , limits amount of usable communication data same key more intelligent cryptographic attacks.


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