Currently I am working on PRESENT block cipher implementation (Hardware) and I am unable to understand the role of round counter in key scheduling part of cipher.
Can some share some insight on round counter and its working?
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3$\begingroup$ Can you say more about what research you've already done with references, and be more specific about where you're stuck? $\endgroup$– Squeamish OssifrageSep 13, 2017 at 22:02
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$\begingroup$ I would assume it has the same purpose as Rcon in the AES key schedule $\endgroup$– Richie FrameSep 14, 2017 at 9:54
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1 Answer
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to prevent self-similarity of key scheduling
The importance of constant addition (not only present cipher) appears in preventing key schedule-based attacks such as slide attack ,related key attacks and other structural attacks such as: invariant subspace attack , and nonlinear invariant subspace attacks.
paragraph 5.4 Key schedule attacks in original Present Block cipher answers your questions.
