{"action":"created","issue":{"url":"https://api.github.com/repos/w3c/encrypted-media/issues/83","labels_url":"https://api.github.com/repos/w3c/encrypted-media/issues/83/labels{/name}","comments_url":"https://api.github.com/repos/w3c/encrypted-media/issues/83/comments","events_url":"https://api.github.com/repos/w3c/encrypted-media/issues/83/events","html_url":"https://github.com/w3c/encrypted-media/issues/83","id":103582945,"number":83,"title":"\"tracked\" sessions: Does \"record of key usage\" need not be updated each time a block is decrypted?","user":{"login":"ddorwin","id":9738764,"avatar_url":"https://avatars.githubusercontent.com/u/9738764?v=3","gravatar_id":"","url":"https://api.github.com/users/ddorwin","html_url":"https://github.com/ddorwin","followers_url":"https://api.github.com/users/ddorwin/followers","following_url":"https://api.github.com/users/ddorwin/following{/other_user}","gists_url":"https://api.github.com/users/ddorwin/gists{/gist_id}","starred_url":"https://api.github.com/users/ddorwin/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/ddorwin/subscriptions","organizations_url":"https://api.github.com/users/ddorwin/orgs","repos_url":"https://api.github.com/users/ddorwin/repos","events_url":"https://api.github.com/users/ddorwin/events{/privacy}","received_events_url":"https://api.github.com/users/ddorwin/received_events","type":"User","site_admin":false},"labels":[{"url":"https://api.github.com/repos/w3c/encrypted-media/labels/blocked","name":"blocked","color":"fad8c7"}],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":2,"created_at":"2015-08-27T19:58:56Z","updated_at":"2015-09-03T16:01:42Z","closed_at":null,"body":"Pull request #54 specifies that the _record of key usage_ be updated every time a key is used to decrypt a block. I wonder whether we need to _require_ this level of granularity. We should definitely be clear about what authors can expect and the minimum granularity implementations must achieve, but I'm not sure requiring per-decrypted-block granularity is necessary to support the relevant use cases for the `\"tracked\"` session feature.\r\n\r\nThe reasonable minimum granularity probably depends on when this information is persisted. Thus, this issue is blocked on issue #82. Issue #80, whether to track key or session usage, may also affect this issue."},"comment":{"url":"https://api.github.com/repos/w3c/encrypted-media/issues/comments/137495537","html_url":"https://github.com/w3c/encrypted-media/issues/83#issuecomment-137495537","issue_url":"https://api.github.com/repos/w3c/encrypted-media/issues/83","id":137495537,"user":{"login":"mwatson2","id":7593867,"avatar_url":"https://avatars.githubusercontent.com/u/7593867?v=3","gravatar_id":"","url":"https://api.github.com/users/mwatson2","html_url":"https://github.com/mwatson2","followers_url":"https://api.github.com/users/mwatson2/followers","following_url":"https://api.github.com/users/mwatson2/following{/other_user}","gists_url":"https://api.github.com/users/mwatson2/gists{/gist_id}","starred_url":"https://api.github.com/users/mwatson2/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/mwatson2/subscriptions","organizations_url":"https://api.github.com/users/mwatson2/orgs","repos_url":"https://api.github.com/users/mwatson2/repos","events_url":"https://api.github.com/users/mwatson2/events{/privacy}","received_events_url":"https://api.github.com/users/mwatson2/received_events","type":"User","site_admin":false},"created_at":"2015-09-03T16:01:42Z","updated_at":"2015-09-03T16:01:42Z","body":"I think this issue can be addressed by addressing the required accuracy of the time fields in the _record of key usage_. Specifically, we should indicate that this is implementation-dependent. If there is agreement we could specify a minimum accuracy.\r\n\r\nKeeping the updates on the block decrypted procedure allows for implementations to support whatever accuracy they choose. Obviously, an implementation does not have to actually update the record more often than the accuracy it supports to achieve the correct observable behavior."}}