{"action":"created","issue":{"url":"https://api.github.com/repos/libtom/libtomcrypt/issues/436","repository_url":"https://api.github.com/repos/libtom/libtomcrypt","labels_url":"https://api.github.com/repos/libtom/libtomcrypt/issues/436/labels{/name}","comments_url":"https://api.github.com/repos/libtom/libtomcrypt/issues/436/comments","events_url":"https://api.github.com/repos/libtom/libtomcrypt/issues/436/events","html_url":"https://github.com/libtom/libtomcrypt/pull/436","id":358955071,"node_id":"MDExOlB1bGxSZXF1ZXN0MjE0NTYyOTQz","number":436,"title":"Implement ecc_recover_key to recover public key from hash+signature","user":{"login":"rmw42","id":37781645,"node_id":"MDQ6VXNlcjM3NzgxNjQ1","avatar_url":"https://avatars0.githubusercontent.com/u/37781645?v=4","gravatar_id":"","url":"https://api.github.com/users/rmw42","html_url":"https://github.com/rmw42","followers_url":"https://api.github.com/users/rmw42/followers","following_url":"https://api.github.com/users/rmw42/following{/other_user}","gists_url":"https://api.github.com/users/rmw42/gists{/gist_id}","starred_url":"https://api.github.com/users/rmw42/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/rmw42/subscriptions","organizations_url":"https://api.github.com/users/rmw42/orgs","repos_url":"https://api.github.com/users/rmw42/repos","events_url":"https://api.github.com/users/rmw42/events{/privacy}","received_events_url":"https://api.github.com/users/rmw42/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":36,"created_at":"2018-09-11T09:10:12Z","updated_at":"2018-09-30T14:28:04Z","closed_at":null,"author_association":"NONE","pull_request":{"url":"https://api.github.com/repos/libtom/libtomcrypt/pulls/436","html_url":"https://github.com/libtom/libtomcrypt/pull/436","diff_url":"https://github.com/libtom/libtomcrypt/pull/436.diff","patch_url":"https://github.com/libtom/libtomcrypt/pull/436.patch"},"body":"This patch implements ECC public key recovery from hash+signature.\r\n\r\nThere are only a small number of possible public keys, typically 2, corresponding to the 'r' value in an elliptic-curve signature. These can be represented by a single parity bit - as with X9.62 compressed keys - in addition to the signature, rather than pre-sharing the public key. This is used in Bitcoin/Ethereum to avoid an explicit representation of the public key, saving space in messages.\r\n\r\necc_recover_key() takes a signature and message hash and an additional \"recovery ID\" value to specify which of the possible public keys to recover. Parameters are very similar to ecc_verify_hash(), but the public key is the output rather than an input.\r\n\r\nSee https://crypto.stackexchange.com/questions/18105/how-does-recovering-the-public-key-from-an-ecdsa-signature-work for the underlying maths.\r\n\r\nCheers,\r\n---\r\nRuss\r\n\r\n### Checklist\r\n\r\n* [x] documentation is added or updated\r\n* [x] tests are added or updated"},"comment":{"url":"https://api.github.com/repos/libtom/libtomcrypt/issues/comments/425724595","html_url":"https://github.com/libtom/libtomcrypt/pull/436#issuecomment-425724595","issue_url":"https://api.github.com/repos/libtom/libtomcrypt/issues/436","id":425724595,"node_id":"MDEyOklzc3VlQ29tbWVudDQyNTcyNDU5NQ==","user":{"login":"sjaeckel","id":294374,"node_id":"MDQ6VXNlcjI5NDM3NA==","avatar_url":"https://avatars2.githubusercontent.com/u/294374?v=4","gravatar_id":"","url":"https://api.github.com/users/sjaeckel","html_url":"https://github.com/sjaeckel","followers_url":"https://api.github.com/users/sjaeckel/followers","following_url":"https://api.github.com/users/sjaeckel/following{/other_user}","gists_url":"https://api.github.com/users/sjaeckel/gists{/gist_id}","starred_url":"https://api.github.com/users/sjaeckel/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/sjaeckel/subscriptions","organizations_url":"https://api.github.com/users/sjaeckel/orgs","repos_url":"https://api.github.com/users/sjaeckel/repos","events_url":"https://api.github.com/users/sjaeckel/events{/privacy}","received_events_url":"https://api.github.com/users/sjaeckel/received_events","type":"User","site_admin":false},"created_at":"2018-09-30T14:28:04Z","updated_at":"2018-09-30T14:28:04Z","author_association":"MEMBER","body":":+1: "}}
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