The way that the author uses pure Excel formulas (no VBA or macros) to compute a QR Code from scratch is similar to how I used pure Excel to compute ciphers:
Thanks! I have another piece of work that shows the internal computations. I implemented hashes and cipher in short Python code. You can insert debugging prints easily to show the intermediate values. https://www.nayuki.io/page/cryptographic-primitives-in-plain...
(Pure) Excel is a form of dataflow programming --- the sequencing is implicit, but the flow of values is explicit. For algorithms that don't have arbitrary input-dependent looping, it is relatively easy to implement.
* AES cipher internals in Excel: https://www.nayuki.io/page/aes-cipher-internals-in-excel
* DES cipher internals in Excel: https://www.nayuki.io/page/des-cipher-internals-in-excel