Is this possible?

[reflector]

Is it possible to change the private key of a bitcoin (or other altcoin) wallet, otherwise keeping the wallet *the same*, and render the old private key useless?
I'm betting this shows a some fundamental misunderstanding of cryptography, but please humor me.

[DeathAndTaxes]

A wallet is a collection of addresses.  So if you mean change the private key and keep the address then the answer is no.  If you mean change the private keys and replace your addresses (lose the old ones and gain new ones) then sure but I can't see why you would want to do that.

[ForgottenPassword]

A wallert is a collection of addresses.  So if you mean change the private key and keep the address then the answer is no.  If you mean change the private key and lose the old addresses while gaining new ones then sure but I can't see why you would want to do that.

He uses the word wallet but my gut tells me he's talking about the Bitcoin address.

I think he means change the private key without changing the address.  So for example if your private key was compromised you could "update" it to a new one while keeping the same address.

No this is not possible. The Bitcoin address is derived from the private key.

[reflector]

I guess it would help to explain why I ask.  There is a coin called slimcoin that uses Proof of Burn, where coins are "burned", then continue burn (aka decay, aka mint new coins) while the wallet is running.  One issue that has cropped up is that the only way a user can sell his wallet, burnt coins included, is to sell his private key (which he has a copy of).

[ForgottenPassword]

I guess it would help to explain why I ask.  There is a coin called slimcoin that uses Proof of Burn, where coins are "burned", then continue burn (aka decay, aka mint new coins) while the wallet is running.  One issue that has cropped up is that the only way a user can sell his wallet, burnt coins included, is to sell his private key (which he has a copy of).

Sounds like that altcoin has a serious flaw then, because if you buy someones private keys, the original owner still has access to the funds. Not a whole lot you can do about that really.

Why would burnt coins have value though?

[DeathAndTaxes]

I guess it would help to explain why I ask.  There is a coin called slimcoin that uses Proof of Burn, where coins are "burned", then continue burn (aka decay, aka mint new coins) while the wallet is running.  One issue that has cropped up is that the only way a user can sell his wallet, burnt coins included, is to sell his private key (which he has a copy of).

There is nothing client side that could change that.   The protocol could be hardforked to allow "signing over" burnt coins to a new keypair.

[DeathAndTaxes]

Why would burnt coins have value though?

"Miners" burn coins to gain the ability to mine blocks in the future.

[reflector]

I'm not explaining very well.  There are actually 3 ways to mint coins with slimcoin:  proof of work, proof of stake, and proof of burn.  After minting coins through PoW, a user may choose to burn his coins, which will, in turn, generate new slimcoins that can be burnt or spent the same as the coins generated through PoW or PoS.   The problem is that the burnt coins are tied to the wallet, and cannot be transferred.  It's not necessarily a fatal flaw, and may have even been done by design, but it got me curious.

[reflector]

I guess it would help to explain why I ask.  There is a coin called slimcoin that uses Proof of Burn, where coins are "burned", then continue burn (aka decay, aka mint new coins) while the wallet is running.  One issue that has cropped up is that the only way a user can sell his wallet, burnt coins included, is to sell his private key (which he has a copy of).

There is nothing client side that could change that.   The protocol could be hardforked to allow "signing over" burnt coins to a new keypair.

Hmm.  That doesn't seem like a practical solution, but maybe something to work with.