I want to store information deniably. So there would be a fixed sized block of data, say one megabyte, increasing by multiples of 8 as needed. This would contain various items of information that one could extract by supplyin a secret, symmetric, key. A random key would extract a block of gibberish of random length There would be no indication as to how many bits of meaningful data were stored in the block, though obviously they would have to add up to less than the size of the block. So one could store one's password list under one key, and the location of the dead bodies under another key, and absent that key, there would be no evidence that they key, or information hidden under that key, existed. What is a good algorithm for this?