No, it is trivial to block 100% of them. A proposal to do just that appeared on the bitcoin-development mailing list yesterday from Peter Todd. This proposed change would relay zero transactions with multisig outputs.
Most of the world is moving to P2SH for multisig, leaving the remaining "bare multisig" users mastercoin, counterparty, etc.
Isn't Peter Todd working on Mastercoin? Why would he propose that?
Think about it. Mastercoin is a competitor to Counterparty. Mastercoin is already aware of, and working on solving this storage-in-multisig problem.
Peter Todd's proposal simultaneously (a) benefits Mastercoin, (b) disadvantages Counterparty, and (c) presents a proposal that portions of the developer and mining community
already find agreeable.
You realize I
also work for Counterparty. You also know I CC'd them on my email where I proposed getting rid of bare CHECKMULTISIG to the bitcoin-
security mailing list with regard to the sigop vulnerability I responsibly disclosed. (which I note that Gavin and others disclosed publicly on IRC a few hours later rather than responsibly fixing it) I notified Counterparty specifically to make sure they got the heads up that this may be an issue for them so they could upgrade their protocol. This is easily done - they might find my recent post on
Embedded consensus system upgrade procedures useful. More generally re: blocking they might be interested in my research, such as
Censorship-resistance via timelock crypto for embedded consensus systems and Mastercoin's way of embedding data in what looks to be valid pubkeys, among other things. FWIW my usual way of communicating to the Mastercoin developers has been to write up a public document so that everyone gets access to the results of my work; my agreement with everyone I work for is that for all IP both parties have the right to use the IP however they see fit, including public release.
My position with regard to competitors in the decentralized finance space is as follows:
I'll also point out that while Mastercoin is my main commitment, I have pre-existing obligations with Litecoin to implement a soft-fork upgrade they need, as well as improve the scalability of Litecoin - and by extension Bitcoin - with blockchain pruning. I'm also continuing my consulting work with Colored Coins, and recently agreed to work with Counterparty to do a security audit of their code and protocol. Of course, some people would question why Mastercoin's Chief Scientist is working with "the competition", but remember our real competition isn't each other, it's enormously larger field of centralized finance. I strongly believe that we have far more to gain by working with each other and growing the tiny field of decentralized finance in general then we have to gain by pointless in-fighting.
http://mastercointalk.org/index.php?topic=155.msg466#msg466