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diff --git a/src/test/hs_indexes.py b/src/test/hs_indexes.py
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+#
+# The hidden service subsystem has two type of index. The first type is a
+# value that each node in the network gets assigned to using their identity
+# key which is their position in the hashring. (hs_build_hsdir_index()).
+#
+# The second type is a value that both the client and service computes to
+# store/fetch the descriptor on the hashring. (hs_build_hs_index()).
+#
+
+import sys
+import hashlib
+import struct
+import base64
+
+# Python 3.6+, the SHA3 is available in hashlib natively. Else this requires
+# the pysha3 package (pip install pysha3).
+if sys.version_info < (3, 6):
+    import sha3
+    # Test vector to make sure the right sha3 version will be used. pysha3 < 1.0
+    # used the old Keccak implementation. During the finalization of SHA3, NIST
+    # changed the delimiter suffix from 0x01 to 0x06. The Keccak sponge function
+    # stayed the same. pysha3 1.0 provides the previous Keccak hash, too.
+    TEST_VALUE = "e167f68d6563d75bb25f3aa49c29ef612d41352dc00606de7cbd630bb2665f51"
+    if TEST_VALUE != sha3.sha3_256(b"Hello World").hexdigest():
+        print("pysha3 version is < 1.0. Please install from:")
+        print("https://github.com/tiran/pysha3https://github.com/tiran/pysha3")
+        sys.exit(1)
+
+# The first index we'll build is the position index in the hashring that is
+# constructed by the hs_build_hsdir_index() function. Construction is:
+#   SHA3-256("node-idx" | node_identity |
+#            shared_random_value | INT_8(period_length) | INT_8(period_num) )
+
+PREFIX = "node-idx".encode()
+# 32 bytes ed25519 pubkey.
+IDENTITY = ("\x42" * 32).encode()
+# SRV is 32 bytes.
+SRV = ("\x43" * 32).encode()
+# Time period length is a 8 bytes value.
+PERIOD_LEN = 1440
+# Period number is a 8 bytes value.
+PERIOD_NUM = 42
+
+data = struct.pack('!8s32s32sQQ', PREFIX, IDENTITY, SRV, PERIOD_NUM,
+                                  PERIOD_LEN)
+hsdir_index = hashlib.sha3_256(data).hexdigest()
+
+print("[hs_build_hsdir_index] %s" % (hsdir_index))
+
+# The second index we'll build is where the HS stores and the client fetches
+# the descriptor on the hashring. It is constructed by the hs_build_hs_index()
+# function and the construction is:
+#   SHA3-256("store-at-idx" | blinded_public_key |
+#            INT_8(replicanum) | INT_8(period_num) | INT_8(period_length) )
+
+PREFIX = "store-at-idx".encode()
+# 32 bytes ed25519 pubkey.
+PUBKEY = ("\x42" * 32).encode()
+# Replica number is a 8 bytes value.
+REPLICA_NUM = 1
+# Time period length is a 8 bytes value.
+PERIOD_LEN = 1440
+# Period number is a 8 bytes value.
+PERIOD_NUM = 42
+
+data = struct.pack('!12s32sQQQ', PREFIX, PUBKEY, REPLICA_NUM, PERIOD_LEN,
+                                   PERIOD_NUM)
+hs_index = hashlib.sha3_256(data).hexdigest()
+
+print("[hs_build_hs_index]   %s" % (hs_index))