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Say you have a message and you run it through an all-or-nothing transform. A transform that requires every single block in the correct order in order to recover any data. Each block is indistinguishable from random noise. Now shuffle them using a seeded crypto RNG.

Say the transform gives you at least 34 blocks (which can be arranged in ~2^128 permutations). Can this structure be considered safe? There's no actual key involved, unless you count the RNG seed.

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  • $\begingroup$ The RNG seed is a key, as it needs to be kept secret for security, and you need it to decrypt the ciphertext. You’ve invented a very slow “wide” block cipher based on a keyed permutation (deterministic shuffling) $\endgroup$ – rmalayter Aug 21 '18 at 2:15

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