[Cryptography] Electronic currency revived after 20-year hiatus

[Allen]

>
> That's the thing with proof-of-work: you get that guarantee even if miners
> aren't honest.


Actually, with PoW, there is no guarantee--there is just a probabilistic
property subject to certain assumptions about computing resources and how
they are expended.  In fact, even if the miners are honest at the time,
later miners can go back and rewrite the blockchain at any time by creating
a higher cumulative PoW.  Conversely, with block signing and key rotation,
you do get a guarantee--if a majority of the miners are honest at the time
and overwrite their private signing key after each block, that does
guarantee the block is permanent and can never be revised.  Note that
neither system (and I believe no system) is going to work if a majority of
miners are dishonest, so I don't think that assumption places a higher
burden on either system.
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