This video claims Segregated Witness is insecure because no one has an incentive to process (witness) the extended signature block.
It claims that as the hashing power increases over 50%, you would be a fool (not a Nash equilibrium) to waste processing power on extended blocks containing the signatures, when the real money is in the transactions containing fees. This means anyone can feed a block with any transaction they want, since no one is checking signatures. (Paraphrased.)
From what I understand, Segregated Witness transaction addresses start with a 3 and are multi-signature addresses. So you have to sign, and someone (who?) also has to sign for the transaction to go through. All of these signatures are placed into an extended block.
- Is the extended block also placed on the main blockchain?
- Who processes the extended block containing signatures?
- What incentive do they have to process the extended signature block?
- Does the extended block have fees?
- Who is the 3rd party signer for segregated witnesses multi-sig addresses?