How do we expand the abbreviation “Rcon” used in the Rijndael key schedule?
I know what it is, I know how it works; I just do not know for what it is a shortcut for. I mean: if "Sbox" is "Substitution box", then "Rcon" stands for… ?
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RCon == Round Constant
It's a value that slightly modifies how each round operates. Without it, AES might be vulnerable to a (related key) slide attack. Such an attack would probably not be of practical interest, however since it's so easy to avoid it (by including the RCon), it makes sense to.