Overall, super duper awesome. :) Tweeted this post. I do have a concern about 2-of-2 arrangements. To me, this screams "twice as fragile" if not done properly; and I've seen a few naive implementations in the field that seemed quite fragile.
2FA/2-of-2 does solve the common problem of single device compromise. It also makes funds unspendable if -either- device's keys become lost. On Sat, Nov 8, 2014 at 5:04 PM, Mike Hearn <m...@plan99.net> wrote: > Here is a summary of current developments in the space of decentralised > 2-factor Bitcoin wallets. I figured some people here might find it > interesting. > > There has been very nice progress in the last month or two. Decentralised > 2FA wallets run on a desktop/laptop and have a (currently always Android) > smartphone app to go with them. Compromise of the wallet requires compromise > of both devices. > > Alon Muroch and Chris Pacia have made huge progress on "Bitcoin > Authenticator", their (HD) wallet app. The desktop side runs on > Win/Mac/Linux and the mobile side runs on Android. Sending money from the > desktop triggers a push notification to the mobile side, which presents the > transaction for confirmation. Additionally the desktop wallet has a variety > of other features like OneName integration. It's currently in alpha, but I > suspect it will be quite popular once released due to its focus on UI and > the simple mobile security model. I've tried it out and it worked fine. > > https://www.bitcoinauthenticator.org/ > https://github.com/cpacia/BitcoinAuthenticator/commits/master (mobile) > https://github.com/negedzuregal/BitcoinAuthWallet (desktop) > > Bitcoin Authenticator uses P2SH/CHECKMULTISIG to provide the 2-factor > functionality. However, this has various downsides that are well known: > less support for the address type and larger transactions that waste block > chain space + result in higher fees. > > To solve this problem Christopher Mann and Daniel Loebenberger from Uni Bonn > have ported the efficient DSA 2-of-2 signing protocol by MacKenzie and > Reiter to ECDSA, and implemented their own desktop/Android wallet app pair > showing that it works and has good enough performance. This means that P2SH > / CHECKMULTISIG is no longer required for the two factor auth case, and thus > it's as cheap as using regular addresses. > > https://github.com/ChristopherMann/2FactorWallet > https://eprint.iacr.org/2014/629.pdf > > Their protocol uses an interesting combination of ECDSA, Paillier > homomorphic encryption and some zero knowledge proofs to build a working > solution for the 2-of-2 case only. Their app bootstraps from a QR code that > includes a TLS public key and IP address of the desktop: the mobile app then > connects to it directly, renders the transaction and performs the protocol > when the user confirms. The protocol is online, so both devices must be > physically present. > > Their code is liberally licensed and looks easy to integrate with Alon and > Chris' more user focused work, as both projects are built with Android and > the latest bitcoinj. If someone is interested, merging Christopher/Daniel's > code into the bitcoinj multisig framework would be a useful project, and > would make it easier for wallet devs to benefit from this work. I can write > a design doc to follow if needed. > > Currently, neither of these projects implement support for BIP70, so the > screen you see when signing the transaction is hardly user friendly or > secure: you just have to trust that the destination address you're paying to > isn't tampered with. Support for sending a full payment request between > devices is the clear next step once these wallets have obtained a reasonable > user base and are stable. > > > > ------------------------------------------------------------------------------ > > _______________________________________________ > Bitcoin-development mailing list > Bitcoin-development@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/bitcoin-development > -- Jeff Garzik Bitcoin core developer and open source evangelist BitPay, Inc. https://bitpay.com/ ------------------------------------------------------------------------------ _______________________________________________ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development