Added hare protocol messages representation in protobuf

hare/pb/hare.proto

@@ -0,0 +1,44 @@
+syntax = "proto3";
+
+package pb;
+option go_package = "pb";
+
+// top message of the protocol
+message HareMessage {
+    bytes pubKey = 1;
+    bytes innerSig = 2; // sign inner message
+    InnerMessage message = 3;
+    bytes outerSig = 4; // optional. sign also certificate
+    Certificate cert = 5; // optional
+}
+
+// the certificate
+message Certificate {
+    repeated bytes blocks = 1; // the committed set S
+    repeated HareMessage commits = 2; // a collection of commit messages
+    bytes aggSig = 3; // aggregated sig for commits
+}
+
+// safe value proof message
+message SVP {
+    repeated HareMessage statuses = 1; // a collection of status messages
+    bytes aggSig = 2; // aggregated sig for statuses
+    Certificate cert = 3;
+}
+
+// basic message
+message InnerMessage {
+    enum Type { // message type
+        STATUS = 0;
+        PROPOSAL = 1;
+        COMMIT = 2;
+        NOTIFY = 3;
+    }
+    Type type = 1;
+    bytes layer = 2;
+    uint32 k = 3; // the iteration
+    uint32 ki = 4;
+    repeated bytes blocks = 5; // the set S. optional for commit message in a certificate
+    bytes roleProof = 6; // role is implicit by message type, this is the proof
+    SVP svpProof = 7; // optional. only for proposal messages
+}