{"action":"closed","issue":{"url":"https://api.github.com/repos/zcash/zips/issues/143","repository_url":"https://api.github.com/repos/zcash/zips","labels_url":"https://api.github.com/repos/zcash/zips/issues/143/labels{/name}","comments_url":"https://api.github.com/repos/zcash/zips/issues/143/comments","events_url":"https://api.github.com/repos/zcash/zips/issues/143/events","html_url":"https://github.com/zcash/zips/issues/143","id":306070523,"number":143,"title":"Specify Sapling commitment tree depth of 32.","user":{"login":"nathan-at-least","id":4369700,"avatar_url":"https://avatars1.githubusercontent.com/u/4369700?v=4","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":[{"id":869849619,"url":"https://api.github.com/repos/zcash/zips/labels/Sapling","name":"Sapling","color":"29ad0f","default":false},{"id":300525226,"url":"https://api.github.com/repos/zcash/zips/labels/protocol%20spec","name":"protocol spec","color":"8dc6eb","default":false}],"state":"closed","locked":false,"assignee":{"login":"daira","id":643204,"avatar_url":"https://avatars2.githubusercontent.com/u/643204?v=4","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},"assignees":[{"login":"daira","id":643204,"avatar_url":"https://avatars2.githubusercontent.com/u/643204?v=4","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}],"milestone":null,"comments":1,"created_at":"2018-03-16T20:43:33Z","updated_at":"2018-03-19T00:04:00Z","closed_at":"2018-03-19T00:04:00Z","author_association":"NONE","body":"Let's specify the Sapling commitment depth is 32. The \"going depth\" has been 29 in keeping with Sprout. The tradeoffs for switching from 29 to 32 for Sapling are:\r\n\r\n- proving time cost increase benchmarked around 2.5%\r\n- memory increase of ~200 KiB against something OTOO ~20 MiB, so ~1%\r\n- little to no extra code complexity since this depth is parameterized\r\n\r\nOne argument Zooko has made is that we want to update people's expectations that the commitment tree will be short lived due to a \"epoch accounting\" mechanism, where there are period global monetary base audits, and there's no reason to add overhead for capacity we don't plan to use.\r\n\r\nBy contrast I want to continually anticipate that *our* roadmap for Zcash becomes superceded by a larger group of stakeholders. Therefore I think it's worth having more breathing room in the protocol for an uncertain future."}}
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