add bft_sm.py

quarkchain/experimental/bft_sm.py

@@ -0,0 +1,95 @@
+# Implement SM(m) algorithm in L. Lamport, R. Shostak, and M. Pease, 1982, "The Byzantine Generals Problem"
+# Some notes:
+# - Order is an integer
+# - Commander is always traitor as loyal command case is trival
+
+import collections
+import random
+
+
+def choice(orders):
+    return min(orders)
+
+
+class Message:
+    def __init__(self, order, sigs):
+        self.order = order
+        self.sigs = sigs
+
+    def signMessage(self, nodeId):
+        newSigs = self.sigs[:]
+        newSigs.append(nodeId)
+        return Message(self.order, newSigs)
+
+    def isAllTraitors(self, M):
+        for sig in self.sigs:
+            if sig >= M:
+                return False
+        return True
+
+    def toString(self):
+        s = str(self.order)
+        for sig in self.sigs:
+            s = "{}:{}".format(s, sig)
+        return s
+
+
+# # of nodes
+N = 5
+
+# # of traitors
+M = 3
+
+# SM(m)
+m = 2
+
+trials = 10
+
+for trial in range(trials):
+    orders_set = [set() for i in range(N)]
+
+    order = random.randint(0, 10000)
+
+    message_queue = collections.deque()
+    message_queue.append((Message(order, []), 0))
+
+    while len(message_queue) != 0:
+        msg, nodeId = message_queue.popleft()
+        print("Node {}: Receive {}".format(nodeId, msg.toString()))
+        if nodeId < M:
+            # Traitor
+            if len(msg.sigs) == m + 1:
+                continue
+
+            canForge = msg.isAllTraitors(M)
+            for i in range(1, N):
+                if i in msg.sigs or i == nodeId:
+                    continue
+                newMsg = msg.signMessage(nodeId)
+                if canForge:
+                    newMsg.order = random.randint(0, 10000)
+                message_queue.append((newMsg, i))
+
+        else:
+            # Loyal
+
+            # Order exist, do nothing.
+            if msg.order in orders_set[nodeId]:
+                continue
+
+            orders_set[nodeId].add(msg.order)
+
+            if len(msg.sigs) == m + 1:
+                continue
+
+            for i in range(1, N):
+                if i in msg.sigs or i == nodeId:
+                    continue
+                message_queue.append((msg.signMessage(nodeId), i))
+
+    c = None
+    for i in range(M, N):
+        if c is None:
+            c = choice(orders_set[i])
+        assert c == choice(orders_set[i])
+    print("All choices are consistent")