Quote from: Dusty on April 04, 2016, 05:57:36 AM

Quote from: franky1 on April 03, 2016, 02:51:42 PM

remember the signatures are moved. to allow them to be processed differently. and old clients cant reject the transaction simply because it doesnt have a signature, if its locked into a confirmed block by a malicious miner. instead its just overlooked.

Your example is invalid because this "malicious miner" can't include an invalid tx in a block, otherwise the whole block would be invalid and hence rejected by the network.

The tx would be invalid, no matter how "funky" it is, because you have to correctly sign the inputs, and if you do not have the private keys of the inputs, you can't provide signatures.

No way to bypass that step, it's how Bitcoin works, and it's made expressly to avoid the attacks you are describing.

to a old client its not invalid.. its just funky.. just like old clients would treat transactions in the future after segwit is released.. still funky to old clients.
remember old clients WILL NOT see the signature area. so they wont validate the transaction. they will just blindly accept it.
if you think old clients wont accept blocks accepting segwit style tx's then segwit is not backward compatible.. (yet it is so that ends that debate)

its not an anyone can spend because of other consensus rules that prevent that too.. (otherwise old clients can abuse segwit later by pushing transactions to nonupgraded pools)

once you understand that segwit is not the exact same as an anyone can spend. but is similar only in the lack of validation part. you will start to see the bigger picture.

my scenario is that while funky in an old client.. its added before segwit clients exist. and so its accepted as funky (op_0). but unspendable due to being funky(different to a true anyonecanspend)

later. separately (please put the first scenario into a box and push it back in time by a month, no longer caring about it because its in the past confirmed into a block but no one can do anything with it back then..)

now new segwits put a checkmark in and dont bother checking the old blocks as they are deemed as pre-checked..
so again even the new segwits wont orphan off the block from a month ago. and if they did, well thats atleast 3000 other blocks they need to orphan off..
(think about it, have a cup of coffee and think about it).

so they havnt orphaned off the first scenario block from one month ago.

but now someone knowing that segwit hasnt checked the old block but has built up a list of utxo's and can see that the first scenario did actually have an output to an address because segwit can now see the sig-ops...

so the owner of the keys to that output now makes a new transaction using a private key to spend that..