[Cryptography] Quillon Graph: A private, post-quantum electronic cash system

[jrzx]

> Consider the scenario: Quantum computers mature in 2045.
> You push an emergency update to your node software.
> Great — new transactions are now post-quantum.
> But what about the 2025 transaction graph that's been
> sitting on-chain for 20 years?

Protected by blockchain immutability. 


Spend authorizations of unspent transaction outputs will not suddenly become forgeable.  When there is a real threat that they might become forgeable in the next decade or so, *then* people will spend them to generate quantum resistant unspent transaction outputs.

Now is far too early to start generating quantum resistant unspent transaction outputs, for quantum computing remains purely theoretical, and quantum resistance is not merely theoretical but hypothetical, indistinguishable in practice from snake oil, grantsmanship, and cryptocurrency scamming.

When we have quantum computers that can maintain quantum coherence while factoring arbitrary sixty four bit numbers, then it might become useful to think about what a quantum resistant algorithm might look like.  Because we will then have tools that can expose some forms of quantum foolishness, magical quantum thinking, quantum bunkum, and quantum flim flam.  Because we will then have better understanding of what real quantum computing cannot do, and put what is hard for quantum computers into our algorithms.
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