The sequence 1,2,1,2,1,2,1... is not indistinguishable from a uniform sequence, at least in the context of cryptography. With high probability, an algorithm th

The sequence 1,2,1,2,1,2,1... is not indistinguishable from a uniform sequence, at least in the context of cryptography. With high probability, an algorithm that checks if all the even indexed inputs are 1 and all the odd indexed inputs are 2 will distinguish that sequence from a uniform random sequence (this is easy to see, as the probability of a sequence of that form being generated by repeatedly tossing a fair coin is very small).