An IND$-$CPA secure encryption scheme might not conceal identities, in the following

sense: given a pair of ciphertexts C$,$ C$$ for equal$-$length messages, it might be $$obvi$-$

ous$$ if the ciphertexts were encrypted using the same random key or were encrypted

using two different random keys. Demonstrate an example of a $($plausibly$)$ IND$-$CPA

secure encryption scheme that has this property of being $$identity$-$revealing$.$ You

do not have to prove that the scheme is IND$-$CPA secure$.$