cryptography , please help

Question

I have a cipher system with $n=p_1\cdot p_2\cdot p_3$ , where every $p_i$ is prime , and a message $M$ ciphered in the following way $$E(M)=(M^{K_1})\mod n$$ I need to find the minimal number of unhidden messages in this system , and I have no clue where to even go.

thank very much for the help in advance

[Editor's note: from the comments an unhidden message is one where $E(M)=M$]

k1 is a key , not defined in the general question , only needs to be legal in the way of exponential cipher — Tomer Avira, Jun 02 '19 at 08:40
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score 1 · Answer 1 · answered Jun 02 '19 at 21:35

1

Hint: the CRT implies that $E(M)=M$ iff $M^{K_1} \pmod{p_i} \equiv M$ for $i=1,2,3$. So think about the prime situation first.

answered Jun 02 '19 at 21:35

Henno Brandsma

242,131

cryptography , please help

1 Answers1