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I'm looking for a cryptographic algorithm that inputs and outputs are both 7 bytes. Is there any such algorithm?

Ilmari Karonen
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Robin Yu
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  • I'd suggest checking out some of our earlier [tag:format-preserving] encryption questions, such as https://crypto.stackexchange.com/questions/504/can-you-create-a-strong-blockcipher-with-small-blocksize-given-a-strong-blockci, https://crypto.stackexchange.com/questions/20035/what-is-the-most-computationally-efficient-way-of-generating-pseudo-random-permu and maybe https://crypto.stackexchange.com/questions/48808/is-there-a-construction-for-a-variable-length-block-cipher-that-uses-a-fixed-len. – Ilmari Karonen Jul 17 '19 at 16:26
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    CTR mode. ${}{}$ – kelalaka Jul 17 '19 at 17:01
  • Are there any security constraints in terms of bits? (i.e. given that 7 times 8-bits per byte would be a total of 56-bits with that much potential maximum security) – Steven Hatzakis Jul 17 '19 at 18:53
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    @kelalaka: That only works if you have an (implicit) unique nonce to go with each piece of data to be encrypted (or if you only ever encrypt one piece of data per key). – Ilmari Karonen Jul 17 '19 at 21:17
  • Reduced-size Feistel network based on keyed XOF. – DannyNiu Jul 18 '19 at 01:13

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