Add peer id suffix to make sub networks

1 files changed, 15 insertions, 1 deletions

diff --git a/lib/identity.ex b/lib/identity.ex
index 229d6c7..f1899df 100644
--- a/lib/identity.ex
+++ b/lib/identity.ex
@@ -1,13 +1,15 @@
 defmodule Shard.Identity do
   use Agent
   require Salty.Sign.Ed25519, as: Sign
+  require Logger
 
   def start_link(_) do
     Agent.start_link(__MODULE__, :init, [], name: __MODULE__)
   end
 
   def init() do
-    {:ok, pk, sk} = Sign.keypair
+    Logger.info "Generating keypair..."
+    {pk, sk} = gen_keypair(Application.get_env(:shard, :peer_id_suffix))
     nick_suffix = pk
                   |> binary_part(0, 3)
                   |> Base.encode16
@@ -18,6 +20,18 @@ defmodule Shard.Identity do
     }
   end
 
+  defp gen_keypair(suffix, n \\ 0) do
+    {:ok, pk, sk} = Sign.keypair
+    if rem(n, 10000) == 0 do
+      Logger.info "#{n}... expected #{:math.pow(256, byte_size(suffix))}"
+    end
+    if :binary.longest_common_suffix([pk, suffix]) == byte_size(suffix) do
+      {pk, sk}
+    else
+      gen_keypair(suffix, n+1)
+    end
+  end
+
   def get_keypair() do
     Agent.get(__MODULE__, &(&1.keypair))
   end