# Tag Info

## Hot answers tagged algorithm-design

4

You are essentially asserting that if $k \equiv 1 \pmod N$, then $a^k \equiv a \pmod N$. This is false in general. The correct assertion is the following: $a^k \equiv a^\ell \pmod N$ if $k\equiv \ell \pmod{\phi(N)}$. In more general group-theoretic terms, if $a$ is an element of order $n$ in a group $G$, then $a^k = a^\ell$ if and only if $k \equiv \ell ... 1 The bottom of page 3 of your second link (the specification for LED) seems pretty clear: "Note that for a 64-bit key$K$, all subkeys are equal to$K$, while for a 128-bit key$K$, the subkeys are alternatively equal to the left part$K^1$and to the right part$K^2$of$K$." Basically, the input master key is split into a sorted list of nibbles, and ... 1 If the attacker can make related-key chosen-plaintext queries, then there is a generic attack that can break any block cipher with$n$-bit keys in$2^{n/2}$time, using$2^{n/2}$related-key queries and$2^{n/2}\$ memory. So against a related-key attacker, the effective strength of a block cipher can be no more than half the key length. However, the ...

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