51% attack, proof of… what?

[Cubic Earth]

We all acknowledge that a 51% attack is possible.  Maybe not likely, maybe not profitable, maybe stupid, but these reasons are not enough, not even when taken together, to stop an attack from happening.

Maybe this idea is already out there, but I am thinking of an approach that uses a web of trust to validate peoples identities.  In addition to finding a very rare hash, you would also need to sign the block with your private key.  And that private key would need to have been signed by some number of other private keys to be valid.  The rule would be that no two blocks in a row can be signed by the same private key, or even keys directly adjacent on the web of trust.

I know what I have described is not presented in enough detail to be workable, but I think with a little bit of though engineering we can make it into something workable.

I can already anticipate one critique, which is that such a concept would be too easy to manipulate, or game.  But what is our goal, as a community?  Hint: It is not to bow down and pay respect to the most powerful computer.  Too powerful a collection of computing power would or could game the system.

I get that one appeal of the SHA-256 hashing is that anyone can run the hardware totally independent and support the network with out any sort of authentication.  Perhaps blocks could be allowed that didn't have a private key attached, but then at least the next two blocks would have to be singed.

The web of trust would be maintained in the blockchain itself.  It would have to start somewhere, but I think our community is small enough still that we can get this going.

tl,dr
• Web of trust to supplement SHA-256
• Successive blocks would have to be signed by different private keys
• This idea is not yet fully developed

[Melbustus]

...
I can already anticipate one critique, which is that such a concept would be too easy to manipulate, or game. 

Yup, and that's a fatal flaw.

But what is our goal, as a community?  Hint: It is not to bow down and pay respect to the most powerful computer.  Too powerful a collection of computing power would or could game the system.
...

The solution is more informal; those that disagree with what the system-gaming "powerful computer" is doing will agree to hard-fork to a different alg. If that's the vast majority of bitcoin users (ie, everyone except that powerful-computer), then bitcoin shifts and the powerful attacker is left with huge power on an effectively unused network.

[Cubic Earth]

The solution is more informal; those that disagree with what the system-gaming "powerful computer" is doing will agree to hard-fork to a different alg. If that's the vast majority of bitcoin users (ie, everyone except that powerful-computer), then bitcoin shifts and the powerful attacker is left with huge power on an effectively unused network.

I would think they would just 51% the new algorithm as soon as it was agreed upon.  That is one of bitcoin's major advantages, it has by far the most invested in supporting hardware.  If they could muster the money and technological ability to compete with all the ASIC's it would probably be pretty easy to take down something else.  And you can bet they would have already planned for it.