> Is this market manipulation?

No

> why do they think that the US government would care about securing cryptocurrencies?

Our largest institutions manage tens of billions of dollars in cryptocurrency and the US government has designated currencies appropriate for the strategic crypto reserve

> Why do they [not care] about the entire world's infrastructures that are based on RSA and elliptic curve algorithms, such as HTTPS

I'm sure they do. But if you had a working quantum computer that could a) get Satoshi's keys or b) read some emails, most people choose door a first. So it's both a smoke test and a high value target with an easy to assess dollar value.

I'm also sure that someone at Google do care about those. It is strange to see a blog post targeting cryptocurrencies while it is certainly a specific case of a much larger problem.

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