diff --git a/network5445/contracts/0x0fa811ac6643a29ad9c17acbed34918a4875f63c/abi b/network5445/contracts/0x0fa811ac6643a29ad9c17acbed34918a4875f63c/abi
new file mode 100644
index 0000000000000000000000000000000000000000..c03a9f40b0274c944e4014825675d183140fec07
--- /dev/null
+++ b/network5445/contracts/0x0fa811ac6643a29ad9c17acbed34918a4875f63c/abi
@@ -0,0 +1 @@
+[{"constant":true,"inputs":[{"name":"hash","type":"bytes32"}],"name":"get","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"name":"hash","type":"bytes32"}],"name":"put","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"}]
diff --git a/network5445/contracts/TimeStampAuthority b/network5445/contracts/TimeStampAuthority
new file mode 120000
index 0000000000000000000000000000000000000000..9e920f677b0b36e75c176a4c26c664b372dec1d2
--- /dev/null
+++ b/network5445/contracts/TimeStampAuthority
@@ -0,0 +1 @@
+0x0fa811ac6643a29ad9c17acbed34918a4875f63c
\ No newline at end of file
diff --git a/src/contract.TimeStampAuthority.sol b/src/contract.TimeStampAuthority.sol
new file mode 100644
index 0000000000000000000000000000000000000000..8b4c4e6cdfaecc65604371f769749c50be53a1ed
--- /dev/null
+++ b/src/contract.TimeStampAuthority.sol
@@ -0,0 +1,21 @@
+// 20180718 Robert Martin-Legene <robert@nic.ar>
+// Time stamp authority
+
+pragma solidity ^0.4.24;
+      
+contract TimeStampAuthority {
+	// This mapping is almost an "associative array"
+	mapping (bytes32 => uint) private hashes;
+
+	// Stores the hash of the document in the mapping
+	function put( bytes32 hash ) public {
+                require( hashes[hash] == 0, "That checksum has already been stored." );
+		hashes[hash] = block.number;
+	}
+
+	// Returns the block number in which the hash was first seen
+	function get( bytes32 hash ) public view returns (uint) {
+                require( hashes[hash] != 0, "That checksum has never been stored." );
+		return hashes[hash];
+	}
+}