Take the 2-minute tour ×  Rather, is it possible for big prime
numbers?  Classroom examples usually involve smaller primes, so
for example if you are given a prime number pair $p = 3$, $q =
13$ you would get $n = 39$ and $e = d = 5$, making encryption
and decryption the same for a message $x$ or ciphertext $x$.
This can be a big problem, e.g. if a server sends you cipher
$x$, you can decrypt it and get the message, then you encrypt
the cipher $x$ itself and if you get the message again then you
know the public key is the same as the private key.  Is this
possible in industry?  share|improve this question  migrated
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@JanDvorak Just comparing the modulus would do it. And searches
on the internet have been performed. –  Maarten Bodewes -
owlstead Jan 6 '13 at 22:22  1 Answer 1  up vote 8 down vote
accepted  No, the public and private exponents will never be the
same for real (that is, not toy