hbaocr · November 30, 2018 07:44 · Jul 11, 2016
diff --git a/ProofOfExistence.sol b/ProofOfExistence.sol
@@ -0,0 +1,105 @@
+/*
+This smartcontract is used to store documents text on the Ethereum blockchain
+and to get the document by document's hash (sha256).
+
+*/
+
+contract ProofOfExistence{
+
+    /* ---- Public variables: */
+    string public created;
+    address public manager; // account that adds info to this smartcontract
+    uint256 public docIndex;   // record's numbers and number of records
+
+    mapping (uint256 => Doc) public indexedDocs; // docIndex => Doc
+    // to get Doc obj call ProofOfExistence.indexedDocs(docIndex);
+
+    mapping (bytes32 => Doc) public sha256Docs; // docHash => Doc
+    // to get Doc obj call ProofOfExistence.docs(docHash);
+    mapping (bytes32 => Doc) public sha3Docs; // docHash => Doc
+    // to get Doc obj call ProofOfExistence.docs(docHash);
+
+
+    /* ---- Stored document structure: */
+
+    struct Doc {
+        uint256 docIndex; // .............................................0
+        string publisher; // publisher's email............................1
+        uint256 publishedOnUnixTime; // block timestamp (block.timestamp).2
+        uint256 publishedInBlockNumber; // block.number...................3
+        string docText; // text of the document...........................4
+        bytes32 sha256Hash; // ...........................................5
+        bytes32 sha3Hash; // .............................................6
+    }
+
+    /* ---- Constructor: */
+
+    function ProofOfExistence(){
+        manager = msg.sender;
+        created = "cryptonomica.net";
+    }
+
+    /* ---- Event:  */
+    // This generates a public event on the blockchain that will notify clients.
+    // In 'Mist' SmartContract page enable 'Watch contract events'
+    event DocumentAdded(uint256 docIndex,
+                        string publisher,
+                        uint256 publishedOnUnixTime);
+
+
+    /* ----- Main method: */
+
+    function addDoc(
+                    string _publisher,
+                    string _docText) returns (bytes32) {
+        // authorization
+        if (msg.sender != manager){
+            // throw;
+            return sha3("not authorized"); //
+            // <- is 'bytes32' too:
+            // "0x8aed0440c9cacb4460ecdd12f6aff03c27cace39666d71f0946a6f3e9022a4a1"
+        }
+
+        // chech if exists
+        if (sha256Docs[sha256(_docText)].docIndex > 0){
+            // throw;
+            return sha3("text already exists"); //
+            // <- is 'bytes32' too:
+            // "0xd42b321cfeadc9593d0a28c4d013aaad8e8c68fc8e0450aa419a130a53175137"
+        }
+        // document number
+        docIndex = docIndex + 1;
+        // add document data:
+        indexedDocs[docIndex] = Doc(docIndex,
+                                    _publisher,
+                                    now,
+                                    block.number,
+                                    _docText,
+                                    sha256(_docText),
+                                    sha3(_docText)
+                                    );
+        sha256Docs[sha256(_docText)] = indexedDocs[docIndex];
+        sha3Docs[sha3(_docText)]   = indexedDocs[docIndex];
+        // add event
+        DocumentAdded(indexedDocs[docIndex].docIndex,
+                      indexedDocs[docIndex].publisher,
+                      indexedDocs[docIndex].publishedOnUnixTime
+                      );
+        // return sha3 of the stored document
+        // (sha3 is better for in web3.js)
+        return indexedDocs[docIndex].sha3Hash;
+    }
+
+    /* ---- Utilities: */
+
+    function () {
+        // This function gets executed if a
+        // transaction with invalid data is sent to
+        // the contract or just ether without data.
+        // We revert the send so that no-one
+        // accidentally loses money when using the
+        // contract.
+        throw;
+    }
+
+}