EFTA02587613.pdf

From: Vincenzo lozzo Sent: Tuesday, August 26, 2014 12:52 PM To: Jeffrey E. Cc: Joi Ito Subject: zero knowledge proof/SNARK One interesting thing I stumbled upon in my reading is ZeroCash, which =s essentially a 'privacy preserving' version of Bitcoin. Now besides the currency itself, what's interesting is that they use a =pecific kind of zero knowledge proof (ZKP) systems called zk-SNARK. I'll save you the full lengthly explanation, but the reason why this is =nteresting is that: 1) ZKP (http://en.wikipedia.org/wiki/Zero-knowledge_proof) can be used =o proof statistically/computationally that a user (A) knows something =ithout reveling the secret itself. eg: A can prove to user (B) that he =nows the password of a certain system without showing the password to B. Usually that requires some kind of interaction between the users (user B asks a round =f questions to user A, if A gets them right then it's statistically =ery unlikely that he got all of them right without knowing the secret) = 2) zk-SNARKs are interesting because: a) They are not interactive b) They are 'short' and easy to prove On top of that essentially you can prove in zero knowledge almost =nything that is 'computable'. What this means is that if we use zk-SNARKS/similar ZKP for our currency =e can enforce arbitrary rules on how the currency is spent ("this coin =s of type X and can only be spent with these following merchants", or =this coin can be spent because it was not obtained illegally and the =uy payed taxes"). I'm exaggerating a bit with expressiveness, but it's =lose. Also this allows us to tweak the privacy vs transparency bit. Generally speaking we have other easier options to do all these things =multi-party signatures, centralized black lists, etc etc), but this is =nteresting. Thoughts? Also Jeffrey, any updates on the govt side of the house? =?xml version=.0" encoding=TF-8"?> <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"> <plist version=.0"> <clict> <key>conversation-idgkey> <integer>299867</integer> <key>date-last-viewed</key> <integer>0</integer> <key>date-received</key> <integer>1409057525</integer> <key>flags</key> EFTA_R1_01768333 EFTA02587613  <integer>8590195713</integer> <key>gmail-label-ids</key> <array> <integer>6</integer> <integer>2</integer> </array> <key>remote-id</key> <string>434491</string> </diet> </plist> 2 EFTA_R1_01768334 EFTA02587614