Made a non-interactive version of the SRP login

Author: ashton314

lib/mix/tasks/demo/srp.ex

@@ -3,8 +3,148 @@ defmodule Mix.Tasks.Demo.Srp do
   @requirements ["loadpaths", "app.config", "app.start"]
 
   use Mix.Task
+  require Logger
+
+  defmodule NonInteractiveClientGood do
+    use Zkp.SrpChor.Chorex, :srpclient
+
+    import Zkp.SrpChor, only: [hash_things: 1]
+
+    @impl true
+    def get_id() do
+      "alice"
+    end
+
+    @impl true
+    def compute_secret(g, n, s, big_b, k, id) do
+      passwd = "hello world"
+
+      a = Enum.random(2..n)
+      big_a = mpow(g, a, n)
+      x = hash_things([id, s, passwd])
+      u = hash_things([big_a, big_b])
+
+      secret_k =
+        mpow(
+          (n + as_int(big_b)) - rem(as_int(k) * as_int(mpow(g, x, n)), n),
+          a + as_int(u) * as_int(x),
+          n
+        )
+
+      m1 = hash_things([big_a, big_b, secret_k])
+      {big_a, m1, secret_k}
+    end
+
+    @impl true
+    def valid_m2?(big_a, m1, k, m2) do
+      hash_things([big_a, m1, k]) == m2
+    end
+
+    defdelegate mpow(a, b, c), to: :crypto, as: :mod_pow
+    defdelegate as_int(n), to: :crypto, as: :bytes_to_integer
+
+    @impl true
+    def gen_verification_token(username, password, salt, g, p) do
+      x = hash_things([username, salt, password])
+      mpow(g, x, p)
+    end
+  end
+
+  defmodule NonInteractiveClientBad do
+    use Zkp.SrpChor.Chorex, :srpclient
+
+    import Zkp.SrpChor, only: [hash_things: 1]
+
+    @impl true
+    def get_id() do
+      "alice"
+    end
+
+    @impl true
+    def compute_secret(g, n, s, big_b, k, id) do
+      passwd = "NOT THE PASSWORD!"
+
+      a = Enum.random(2..n)
+      big_a = mpow(g, a, n)
+      x = hash_things([id, s, passwd])
+      u = hash_things([big_a, big_b])
+
+      secret_k =
+        mpow(
+          (n + as_int(big_b)) - rem(as_int(k) * as_int(mpow(g, x, n)), n),
+          a + as_int(u) * as_int(x),
+          n
+        )
+
+      m1 = hash_things([big_a, big_b, secret_k])
+      {big_a, m1, secret_k}
+    end
+
+    @impl true
+    def valid_m2?(big_a, m1, k, m2) do
+      hash_things([big_a, m1, k]) == m2
+    end
+
+    defdelegate mpow(a, b, c), to: :crypto, as: :mod_pow
+    defdelegate as_int(n), to: :crypto, as: :bytes_to_integer
+
+    @impl true
+    def gen_verification_token(username, password, salt, g, p) do
+      x = hash_things([username, salt, password])
+      mpow(g, x, p)
+    end
+  end
 
   def run(_args) do
-    IO.puts("Hey look running the SRP demo!")
+    Logger.info("Starting non-interactive SRP login demo")
+    Logger.info("Registration: using username 'alice', password 'hello world'")
+    Logger.info("You should see 'Server responds {:registered, \"alice\"}' and 'Client responds :registered'")
+
+    Chorex.start(Zkp.SrpChor.Chorex,
+                 %{ SrpServer => Zkp.SrpServerImpl,
+                 SrpClient => NonInteractiveClientGood },
+                 [{"alice", "hello world"}, :register])
+
+    receive do
+      {:chorex_return, SrpServer, resp} -> IO.puts("Server responds #{inspect resp}")
+    end
+
+    receive do
+      {:chorex_return, SrpClient, resp} -> IO.puts("Client responds #{inspect resp}")
+    end
+
+    Logger.info("Registration successful. Attempting login with good credentials.")
+    Logger.info("You should see the same value twice---this means the server and client have computed the same value.")
+
+    Chorex.start(Zkp.SrpChor.Chorex,
+      %{ SrpServer => Zkp.SrpServerImpl,
+      SrpClient => NonInteractiveClientGood },
+      [])
+
+    receive do
+      {:chorex_return, SrpServer, resp} -> IO.puts("Server responds #{inspect resp}")
+    end
+
+    receive do
+      {:chorex_return, SrpClient, resp} -> IO.puts("Client responds #{inspect resp}")
+    end
+
+    Logger.info("Now trying to login with bad credentials.")
+    Logger.info("You should see server and client rejecting the digest")
+
+    Chorex.start(Zkp.SrpChor.Chorex,
+      %{ SrpServer => Zkp.SrpServerImpl,
+      SrpClient => NonInteractiveClientBad },
+      [])
+
+    receive do
+      {:chorex_return, SrpServer, resp} -> IO.puts("Server responds #{inspect resp}")
+    end
+
+    receive do
+      {:chorex_return, SrpClient, resp} -> IO.puts("Client responds #{inspect resp}")
+    end
+
+    Logger.info("SRP demo complete")
   end
 end

lib/zkp/srp_server_impl.ex

@@ -16,7 +16,6 @@ defmodule Zkp.SrpServerImpl do
 
   @impl true
   def register(ident, salt, token) do
-    {ident, salt, token, @good_n, @good_g}
     :ets.insert_new(@user_tbl, {ident, salt, token, @good_n, @good_g})
   end