feat: finish demo

src/demo.py

@@ -1,3 +1,31 @@
 from tpre import *
 
+# 1
+pk_a, sk_a = GenerateKeyPair(1, ())
+m = b'hello world'
+m = int.from_bytes(m)
+
+# 2
+capsule_ct = Encrypt(pk_a, m)
+
+# 3
+pk_b, sk_b = GenerateKeyPair(1, ())
+
+N = 20
+T = 10
+
+# 5
+rekeys =  GenerateReKey(sk_a, pk_b, N, T)
+
+# 7
+cfrag_cts = []
+
+for rekey in rekeys:
+    cfrag_ct = ReEncrypt(rekey, capsule_ct)
+    cfrag_cts.append(cfrag_ct)
+    
+# 9
+cfrags = mergecfrag(cfrag_cts)
+m = DecryptFrags(sk_b, pk_b, pk_a, cfrags)
+