diff --git a/pkgs/development/python-modules/opentimestamps/default.nix b/pkgs/development/python-modules/opentimestamps/default.nix
new file mode 100644
index 00000000000..1271a46f047
--- /dev/null
+++ b/pkgs/development/python-modules/opentimestamps/default.nix
@@ -0,0 +1,29 @@
+{ lib, buildPythonPackage, fetchFromGitHub, isPy3k
+, bitcoinlib, GitPython, pysha3 }:
+
+buildPythonPackage rec {
+  name = "opentimestamps-${version}";
+  version = "0.2.1";
+  disabled = (!isPy3k);
+
+  src = fetchFromGitHub {
+    owner = "opentimestamps";
+    repo = "python-opentimestamps";
+    rev = "python-opentimestamps-v0.2.1";
+    sha256 = "1cilv1ls9mdqk8zriqfkz7xcl8i1ncm0f89n4c8k4s82kf5y56rm";
+  };
+
+  # Remove a failing test which expects the test source file to reside in the
+  # project's Git repo
+  patchPhase = ''
+    rm opentimestamps/tests/core/test_git.py
+  '';
+
+  propagatedBuildInputs = [ bitcoinlib GitPython pysha3 ];
+
+  meta = {
+    description = "Create and verify OpenTimestamps proofs";
+    homepage = https://github.com/opentimestamps/python-opentimestamps;
+    license = lib.licenses.lgpl3;
+  };
+}
diff --git a/pkgs/development/python-modules/pysha3/default.nix b/pkgs/development/python-modules/pysha3/default.nix
new file mode 100644
index 00000000000..4df98623e11
--- /dev/null
+++ b/pkgs/development/python-modules/pysha3/default.nix
@@ -0,0 +1,19 @@
+{ lib, buildPythonPackage, fetchPypi, pythonOlder }:
+
+buildPythonPackage rec {
+  pname = "pysha3";
+  version = "1.0.2";
+  name = "${pname}-${version}";
+  disabled = pythonOlder "2.7";
+
+  src = fetchPypi {
+    inherit pname version;
+    sha256 = "17kkjapv6sr906ib0r5wpldmzw7scza08kv241r98vffy9rqx67y";
+  };
+
+  meta = {
+    description = "Backport of hashlib.sha3 for 2.7 to 3.5";
+    homepage = https://github.com/tiran/pysha3;
+    license = lib.licenses.psfl;
+  };
+}
diff --git a/pkgs/tools/misc/opentimestamps-client/default.nix b/pkgs/tools/misc/opentimestamps-client/default.nix
new file mode 100644
index 00000000000..a062aa992be
--- /dev/null
+++ b/pkgs/tools/misc/opentimestamps-client/default.nix
@@ -0,0 +1,23 @@
+{ lib, buildPythonApplication, fetchFromGitHub, isPy3k
+, opentimestamps, GitPython, pysocks }:
+
+buildPythonApplication rec {
+  name = "opentimestamps-client-${version}";
+  version = "0.5.1";
+  disabled = (!isPy3k);
+
+  src = fetchFromGitHub {
+    owner = "opentimestamps";
+    repo = "opentimestamps-client";
+    rev = "opentimestamps-client-v0.5.1";
+    sha256 = "0s549xkb75r5wyvjlfmac8a1df6w0y55l98f492zsihdns1d6rzq";
+  };
+
+  propagatedBuildInputs = [ opentimestamps GitPython pysocks ];
+
+  meta = {
+    description = "Command-line tool to create and verify OpenTimestamps proofs";
+    homepage = https://github.com/opentimestamps/opentimestamps-client;
+    license = lib.licenses.lgpl3;
+  };
+}
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 5dac4a2d98a..a632aa818bb 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -16952,6 +16952,8 @@ with pkgs;
 
   openscad = callPackage ../applications/graphics/openscad {};
 
+  opentimestamps-client = python3Packages.callPackage ../tools/misc/opentimestamps-client {};
+
   opentx = callPackage ../applications/misc/opentx { };
 
   opera = callPackage ../applications/networking/browsers/opera {};
diff --git a/pkgs/top-level/python-packages.nix b/pkgs/top-level/python-packages.nix
index 8e4da97d3d4..eea50ebd3eb 100644
--- a/pkgs/top-level/python-packages.nix
+++ b/pkgs/top-level/python-packages.nix
@@ -11081,6 +11081,8 @@ in {
 
   openpyxl = callPackage ../development/python-modules/openpyxl { };
 
+  opentimestamps = callPackage ../development/python-modules/opentimestamps { };
+
   ordereddict = buildPythonPackage rec {
     name = "ordereddict-${version}";
     version = "1.1";
@@ -12916,6 +12918,8 @@ in {
 
   pyrr = callPackage ../development/python-modules/pyrr { };
 
+  pysha3 = callPackage ../development/python-modules/pysha3 { };
+
   pyshp = callPackage ../development/python-modules/pyshp { };
 
   pysmbc = callPackage ../development/python-modules/pysmbc { };