in my cryptography course, we are learning about pseudo randomness and the prefix-preserving function known as CryptoPAn invented in 2002. It is said that the scheme is highly insecure. So in that case, i am leaning towards disproving the pseudorandomness of cryptoPAn. But i am struggling to put it into words.
for your kind information, this is crpytopan : https://handwiki.org/wiki/Crypto-PAn