irreducible Polynomial in a Cipher If we change the irreducible polynomial of the AES to someother irreducible or primitive polynomial, what effect will it have in security?
Yes, we can change the irreducible polynomial of AES to another irreducible polynomial. In doing so we have to implement a change of basis or change the polynomial for the S-Box, this may effect the security. Moreover research had been done on how to enhance the security of AES by changing the irreducible polynomial. See this paper for detailed discussion. 

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