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The Spritz cipher is a "sponge-like" construction that the authors show can be used as a hash, MAC, stream cipher, re-seedable pseudo random number generator, and/or an authenticated cipher.

Apart from some internal control variables, there is an array of size N (call it the state : I set N = 256 for this discussion).

The state is initialized to the identity permutation (ie: s [0] = 0 , s [1] = 1 , ...).

For those modes that require a secret key, the authors first "absorb" the secret key and then "squeeze" out the mask bits and/or a digest.

It occurred to me that by choosing the initial permutation state randomly, would I not be able to consider this as a key in and of itself?

This would allow me to have the full domain of possible keys to choose from (256! in this case).

An example of the MAC mode :

  • Initialize state S with secret permutation (the key)
  • Absorb the message text
  • Absorb STOP
  • Absorb message digest size (in bytes)
  • Squeeze out digest

Are there any security issues raised by doing this?

Would this affect any of the other modes of operation that the authors prescribe?

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