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

[Viktor S. Kristensen]

The question is: If every 'private' transaction you make today becomes a public confession in 20 years, is the blockchain an immutable ledger or an immutable witness against you? Because: "harvest now, decrypt later" attack is real - adversaries could capture encrypted blockchain transactions today and decrypt them in 20 years if QC matures. For financial data with long-term value, it's reasonable to prepare.

When quantum computers can retroactively strip the veil from every encrypted transaction ever recorded on an eternal, immutable chain - do we have 'privacy with an expiration date' or 'delayed total surveillance'? 


The unsettling truth: blockchain's greatest feature (immutability) becomes its greatest liability against HNDL attacks. You can't delete what you encrypted poorly. The chain remembers forever.















Really important if something matters

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søndag den 28. december 2025 kl. 17:34, skrev Ron Garret <ron at flownet.com>:

> 

> 

> > On Dec 27, 2025, at 7:43 PM, Viktor S. Kristensen via cryptography <cryptography at metzdowd.com> wrote:
> > 

> > Most importantly, it’s designed to withstand quantum adversaries from day one.
> 

> 

> Everyone here on the crypo list needs to watch this presentation by our very own Peter Gutman:
> 

> https://www.youtube.com/watch?v=xa4Ok7WNFHY
> 

> It is one of the best assessments of quantum risk that I've seen.
> 

> rg
> 
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