{"action":"created","issue":{"url":"https://api.github.com/repos/Electric-Coin-Company/zcash/issues/406","repository_url":"https://api.github.com/repos/Electric-Coin-Company/zcash","labels_url":"https://api.github.com/repos/Electric-Coin-Company/zcash/issues/406/labels{/name}","comments_url":"https://api.github.com/repos/Electric-Coin-Company/zcash/issues/406/comments","events_url":"https://api.github.com/repos/Electric-Coin-Company/zcash/issues/406/events","html_url":"https://github.com/Electric-Coin-Company/zcash/issues/406","id":114913559,"number":406,"title":"Implement selective transparency","user":{"login":"nathan-at-least","id":4369700,"avatar_url":"https://avatars.githubusercontent.com/u/4369700?v=3","gravatar_id":"","url":"https://api.github.com/users/nathan-at-least","html_url":"https://github.com/nathan-at-least","followers_url":"https://api.github.com/users/nathan-at-least/followers","following_url":"https://api.github.com/users/nathan-at-least/following{/other_user}","gists_url":"https://api.github.com/users/nathan-at-least/gists{/gist_id}","starred_url":"https://api.github.com/users/nathan-at-least/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/nathan-at-least/subscriptions","organizations_url":"https://api.github.com/users/nathan-at-least/orgs","repos_url":"https://api.github.com/users/nathan-at-least/repos","events_url":"https://api.github.com/users/nathan-at-least/events{/privacy}","received_events_url":"https://api.github.com/users/nathan-at-least/received_events","type":"User","site_admin":false},"labels":[{"url":"https://api.github.com/repos/Electric-Coin-Company/zcash/labels/anonymity","name":"anonymity","color":"93b937"},{"url":"https://api.github.com/repos/Electric-Coin-Company/zcash/labels/crypto","name":"crypto","color":"ff6b75"},{"url":"https://api.github.com/repos/Electric-Coin-Company/zcash/labels/maybe%20in%201.0","name":"maybe 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spec and stuff","description":"Necessary stuff:\r\n* `zcp2 aka Trafford` spec ready for scientist review.\r\n* Deliver toy miner implementing \"Generalized Birthday Problem\" PoW\r\n\r\nDesirable stuff:\r\n* Homu, docker build slaves, more betterer CI!\r\n* Help users with bugs, common install snags, feature requests (e.g. RPC improvement)\r\n\r\n**PR:** Blog about Trafford improvements (Faerie gold fix, chained-Pours, etc...)\r\n","creator":{"login":"daira","id":643204,"avatar_url":"https://avatars.githubusercontent.com/u/643204?v=3","gravatar_id":"","url":"https://api.github.com/users/daira","html_url":"https://github.com/daira","followers_url":"https://api.github.com/users/daira/followers","following_url":"https://api.github.com/users/daira/following{/other_user}","gists_url":"https://api.github.com/users/daira/gists{/gist_id}","starred_url":"https://api.github.com/users/daira/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/daira/subscriptions","organizations_url":"https://api.github.com/users/daira/orgs","repos_url":"https://api.github.com/users/daira/repos","events_url":"https://api.github.com/users/daira/events{/privacy}","received_events_url":"https://api.github.com/users/daira/received_events","type":"User","site_admin":false},"open_issues":12,"closed_issues":0,"state":"open","created_at":"2016-02-08T23:44:18Z","updated_at":"2016-02-15T23:56:09Z","due_on":"2016-02-22T00:00:00Z","closed_at":null},"comments":16,"created_at":"2015-11-03T21:23:01Z","updated_at":"2016-02-16T02:54:18Z","closed_at":null,"body":"I'm not sure we already have a ticket for selective transparency, even though we've been discussing it for about a year. Here's a ticket specifically for this feature, which looks something like every zc address also comes with an \"auditing\" key which allows reading all sent/received transaction amounts, but not spending for that address.\r\n\r\ncrosslinks:\r\n\r\n* Here's a mention of it in the use case brainstorm ticket: https://github.com/Electric-Coin-Company/zerocashd/issues/72#issuecomment-74565138\r\n* we also have notes from the January hackfest somewhere. Paging @daira.\r\n\r\nAlso, this sounds very similar to a Monero feature:\r\n\r\n* https://forum.getmonero.org/1/news-announcements-and-editorials/191/editorial-the-value-of-privacy\r\n"},"comment":{"url":"https://api.github.com/repos/Electric-Coin-Company/zcash/issues/comments/184489655","html_url":"https://github.com/Electric-Coin-Company/zcash/issues/406#issuecomment-184489655","issue_url":"https://api.github.com/repos/Electric-Coin-Company/zcash/issues/406","id":184489655,"user":{"login":"daira","id":643204,"avatar_url":"https://avatars.githubusercontent.com/u/643204?v=3","gravatar_id":"","url":"https://api.github.com/users/daira","html_url":"https://github.com/daira","followers_url":"https://api.github.com/users/daira/followers","following_url":"https://api.github.com/users/daira/following{/other_user}","gists_url":"https://api.github.com/users/daira/gists{/gist_id}","starred_url":"https://api.github.com/users/daira/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/daira/subscriptions","organizations_url":"https://api.github.com/users/daira/orgs","repos_url":"https://api.github.com/users/daira/repos","events_url":"https://api.github.com/users/daira/events{/privacy}","received_events_url":"https://api.github.com/users/daira/received_events","type":"User","site_admin":false},"created_at":"2016-02-16T02:54:18Z","updated_at":"2016-02-16T02:54:18Z","body":"@defuse wrote:\r\n> To carry out the \"receive\" operation in Figure 2 of the paper, a<sub>sk</sub> is required in step 3.b.ii.second-bullet-point. A [viewing] key holder who doesn't know a<sub>sk</sub> therefore can't actually complete the the entire \"receive\" and therefore can't be sure that the holder of a<sub>sk</sub> can spend the value the viewkey holder observed them to receive.\r\n\r\nThe second bullet point check is only a check on whether the coin is spent. The viewing key holder can verify that the coin commitment was correct. Whether the coin is spent is not information that the sender's viewing key should grant access to. That is properly only part of the receiver's transaction view, not the sender's.\r\n\r\nNote that only a holder of a<sub>sk</sub> can spend the coin, and PRF<sup>sn</sub> is relied on to be collision-resistant, so the sender can't construct a Pour with a ciphertext that appears valid to a viewing key holder and is \"pre-spent\" unless it holds a<sub>sk</sub>, i.e. it is also the recipient."}}