7.12. We now show how an attack with chosen ciphertext can beused to
break an RSA encryption.
1. Show that the multiplicative property holds for RSA, i.e., showthat the
product of two ciphertexts is equal to the encryption of theproduct of the
two respective plaintexts.
2. This property can under certain circumstances lead to an attack.Assume
that Bob first receives an encrypted message y1 from Alice whichOscar
obtains by eavesdropping. At a later point in time, we assume thatOscar
can send an innocent looking ciphertext y2 to Bob, and that Oscarcan
obtain the decryption of y2 .In practice this could, for instance,happen if
Oscar manages to hack into Bob’s System
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