added all tutorials from lesson 7

period_1/07-mining/702_TX2_A02_Nonce/BlockChain.py

@@ -0,0 +1,25 @@
+from cryptography.hazmat.backends import default_backend
+from cryptography.hazmat.primitives import hashes
+
+class CBlock:
+
+    data = None
+    previousHash = None
+    previousBlock = None
+    def __init__(self, data, previousBlock):
+        self.data = data
+        self.blockHash = None
+        self.previousBlock = previousBlock
+        if previousBlock != None:
+            self.previousHash = previousBlock.computeHash()
+    
+    def computeHash(self):
+        digest = hashes.Hash(hashes.SHA256(), backend=default_backend())
+        digest.update(bytes(str(self.data),'utf8'))
+        digest.update(bytes(str(self.previousHash),'utf8'))
+        return digest.finalize()
+
+    def is_valid(self):
+        if self.previousBlock == None:
+            return True
+        return self.previousBlock.computeHash() == self.previousHash