If interpreted that way, storing the noise and memorizing the offset, it amounts to having a privately stored one-time pad to be used as key... with a passphrase with as many bits in it as the offset. That’s probably not a lot of bits. You are better off storing the data, encrypted with a real pass phrase, wherever you would have stored the random noise stream that is needed to read the data in any case. Don’t roll your own crypto.
Sure, except now you have an equal amount of data that needs to be stored somewhere. The pad is as long as the data. Either you have to encrypt that using some other means, or you do the weak "store offset" method.
