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In academic pursuits, we often have people (and their ideas) who are considered fundamental to the subject, such as Bayes and probability.

In cryptography, it's obvious to see that the Diffie-Hellman problem is fundamental to modern key exchange algorithms.

Can modern day symmetric encryption methods be similarly traced back to particular fundamental roots or building-blocks? If so, what are they?

Is there a common grandparent (or few) that most modern symmetric crypto such as AES or ChaCha can be undeniability related to?

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  • $\begingroup$ AES for example isn't a Feistel cipher, it's a substitution permutation network $\endgroup$ – cisnjxqu Dec 9 '20 at 17:23
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    $\begingroup$ One of the most essential concepts for symmetric crypto may be Shannon's confusion and diffusion principle. $\endgroup$ – cisnjxqu Dec 9 '20 at 17:25
  • $\begingroup$ @cisnjxqu Regarding AES I know. I'm (tentatively) asking whether the SP-network/etc is a little brother of Feistel. Or Feistel with extra pieces. Or whether there is anything that is. $\endgroup$ – Modal Nest Dec 9 '20 at 17:39
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    $\begingroup$ To add to @cisnjxqu's suggestion, Shannon also formulated the concept of a product cipher. And of course, of perfect security. All of these are in the same paper. $\endgroup$ – Luis Casillas Dec 9 '20 at 21:54
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There are a few here.

  1. Block ciphers like DES and its modes are based of Feistel Cipher, AES is based on Rijndael.

  2. Others like FOX64 based on Lai-Massey scheme.

  3. Other are are stream ciphers like RC4.

So, These are some of the schemes which are used in todays symmetric key ciphers.

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  • $\begingroup$ I think you've misunderstood my question, or maybe it isn't clear. I'm asking for the fundamental roots (if any) of modern symmetric ciphers. I'm aware that stream ciphers like ChaCha exist , my question is about the roots of such functions. All of what you've listed are clearly more related to Feistel than Caesar, for example. $\endgroup$ – Modal Nest Dec 9 '20 at 13:56
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    $\begingroup$ AES is not based on Rijndael, AES is Rijndael. Rijndael was selected as part of the AES standardization process to become AES. $\endgroup$ – cisnjxqu Dec 9 '20 at 17:22
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    $\begingroup$ @cisnjxqu: to be more precise, AES is Rijndael restricted to 128 bit block sizes and 128, 192 or 256 bit keys. Rijndael allows for many more options than AES. $\endgroup$ – poncho Dec 9 '20 at 18:05

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