From 0afdf0d145738be9fe09c5d7ed3cbbce35d3a8cd Mon Sep 17 00:00:00 2001
From: Nedelcho Delchev <nedelcho_delchev@abv.bg>
Date: Mon, 20 Nov 2017 18:06:29 +0200
Subject: [PATCH 1/4] Validation for difficulty target

---
 apps/aecore/lib/aecore/chain/worker.ex        | 20 ++++++++++++++---
 apps/aecore/lib/aecore/miner/worker.ex        | 22 ++++++++++---------
 .../utils/blockchain/block_validation.ex      | 10 +++++++--
 .../lib/aecore/utils/blockchain/difficulty.ex |  9 +-------
 apps/aecore/test/aecore_chain_test.exs        | 15 +++++++++----
 apps/aecore/test/aecore_hashcash_test.exs     |  6 ++---
 apps/aecore/test/aecore_validation_test.exs   |  4 +++-
 .../web/controllers/block_controller.ex       |  2 +-
 8 files changed, 56 insertions(+), 32 deletions(-)

diff --git a/apps/aecore/lib/aecore/chain/worker.ex b/apps/aecore/lib/aecore/chain/worker.ex
index f1a9a541..7a9bdf5f 100644
--- a/apps/aecore/lib/aecore/chain/worker.ex
+++ b/apps/aecore/lib/aecore/chain/worker.ex
@@ -11,6 +11,7 @@ defmodule Aecore.Chain.Worker do
   alias Aecore.Utils.Blockchain.BlockValidation
   alias Aecore.Peers.Worker, as: Peers
   alias Aecore.Utils.Persistence
+  alias Aecore.Utils.Blockchain.Difficulty
 
   use GenServer
 
@@ -67,8 +68,23 @@ defmodule Aecore.Chain.Worker do
     Enum.reverse(get_blocks([], start_block_hash, size))
   end
 
+  @spec add_validated_block(%Block{}) :: :ok
+  def add_validated_block(%Block{} = block) do
+    latest_block = latest_block()
+
+    prev_block_chain_state = chain_state()
+    new_block_state = ChainState.calculate_block_state(block.txs)
+    new_chain_state = ChainState.calculate_chain_state(new_block_state, prev_block_chain_state)
+
+    latest_header_hash = BlockValidation.block_header_hash(latest_block.header)
+    blocks_for_difficulty_calculation = get_blocks(latest_header_hash, Difficulty.get_number_of_blocks())
+
+    BlockValidation.validate_block!(block, latest_block, new_chain_state, blocks_for_difficulty_calculation)
+    add_block(block)
+  end
+
   @spec add_block(%Block{}) :: :ok
-  def add_block(%Block{} = block) do
+  defp add_block(%Block{} = block) do
     GenServer.call(__MODULE__, {:add_block, block})
   end
 
@@ -137,8 +153,6 @@ defmodule Aecore.Chain.Worker do
     new_block_txs_index = calculate_block_acc_txs_info(block)
     new_txs_index = update_txs_index(txs_index, new_block_txs_index)
     try do
-      BlockValidation.validate_block!(block, block_map[block.header.prev_hash], new_chain_state)
-
       Enum.each(block.txs, fn(tx) -> Pool.remove_transaction(tx) end)
 
       block_hash = BlockValidation.block_header_hash(block.header)
diff --git a/apps/aecore/lib/aecore/miner/worker.ex b/apps/aecore/lib/aecore/miner/worker.ex
index d694615b..3ff7a3a6 100644
--- a/apps/aecore/lib/aecore/miner/worker.ex
+++ b/apps/aecore/lib/aecore/miner/worker.ex
@@ -138,7 +138,17 @@ defmodule Aecore.Miner.Worker do
         Enum.at(blocks, 1)
     end
     try do
-      BlockValidation.validate_block!(latest_block, previous_block, chain_state)
+
+      BlockValidation.validate_block!(latest_block, previous_block, chain_state, blocks_for_difficulty_calculation)
+
+    catch
+      {:error, _message} ->
+        Logger.error(fn ->
+          "Failed to mine block"
+        end)
+    end
+
+      difficulty = Difficulty.calculate_next_difficulty(blocks_for_difficulty_calculation)
 
       valid_txs = BlockValidation.filter_invalid_transactions_chainstate(ordered_txs_list, chain_state)
       {_, pubkey} = Keys.pubkey()
@@ -152,8 +162,6 @@ defmodule Aecore.Miner.Worker do
 
       latest_block_hash = BlockValidation.block_header_hash(latest_block.header)
 
-      difficulty = Difficulty.calculate_next_difficulty(blocks_for_difficulty_calculation)
-
       unmined_header =
         Header.create(
           latest_block.header.height + 1,
@@ -172,17 +180,11 @@ defmodule Aecore.Miner.Worker do
           Logger.info(fn ->
             "Mined block ##{block.header.height}, difficulty target #{block.header.difficulty_target}, nonce #{block.header.nonce}"
             end)
-          Chain.add_block(block)
+          Chain.add_validated_block(block)
           {:block_found, 0}
 
         {:error, _message} ->
           {:no_block_found, start_nonce + @nonce_per_cycle}
       end
-    catch
-      {:error, _message} ->
-        Logger.error(fn ->
-          "Failed to mine block"
-        end)
-    end
   end
 end
diff --git a/apps/aecore/lib/aecore/utils/blockchain/block_validation.ex b/apps/aecore/lib/aecore/utils/blockchain/block_validation.ex
index 15d6a70b..0f842cec 100644
--- a/apps/aecore/lib/aecore/utils/blockchain/block_validation.ex
+++ b/apps/aecore/lib/aecore/utils/blockchain/block_validation.ex
@@ -7,9 +7,10 @@ defmodule Aecore.Utils.Blockchain.BlockValidation do
   alias Aecore.Structures.Header
   alias Aecore.Structures.SignedTx
   alias Aecore.Chain.ChainState
+  alias Aecore.Utils.Blockchain.Difficulty
 
-  @spec validate_block!(Block.block(), Block.block(), map()) :: {:error, term()} | :ok
-  def validate_block!(new_block, previous_block, chain_state) do
+  @spec validate_block!(Block.block(), Block.block(), map(), list()) :: {:error, term()} | :ok
+  def validate_block!(new_block, previous_block, chain_state, blocks_for_difficulty_calculation) do
 
     is_genesis = new_block == Block.genesis_block() && previous_block == nil
     chain_state_hash = ChainState.calculate_chain_state_hash(chain_state)
@@ -19,6 +20,8 @@ defmodule Aecore.Utils.Blockchain.BlockValidation do
     coinbase_transactions_sum = sum_coinbase_transactions(new_block)
     total_fees = Miner.calculate_total_fees(new_block.txs)
 
+    difficulty = Difficulty.calculate_next_difficulty(blocks_for_difficulty_calculation)
+
     cond do
       # do not check previous block hash for genesis block, there is none
       !(is_genesis || check_prev_hash(new_block, previous_block)) ->
@@ -49,6 +52,9 @@ defmodule Aecore.Utils.Blockchain.BlockValidation do
       new_block.header.version != Block.current_block_version() ->
         throw({:error, "Invalid block version"})
 
+      difficulty != new_block.header.difficulty_target ->
+        throw({:error, "Invalid block difficulty"})
+
       true ->
         :ok
     end
diff --git a/apps/aecore/lib/aecore/utils/blockchain/difficulty.ex b/apps/aecore/lib/aecore/utils/blockchain/difficulty.ex
index e0e23fa1..197c3569 100644
--- a/apps/aecore/lib/aecore/utils/blockchain/difficulty.ex
+++ b/apps/aecore/lib/aecore/utils/blockchain/difficulty.ex
@@ -1,5 +1,4 @@
 defmodule Aecore.Utils.Blockchain.Difficulty do
-  alias Aecore.Chain.Worker, as: Chain
 
   @number_of_blocks 100
   @max_difficulty_change 2
@@ -9,13 +8,7 @@ defmodule Aecore.Utils.Blockchain.Difficulty do
     @number_of_blocks
   end
 
-  @spec calculate_next_difficulty :: integer()
-  def calculate_next_difficulty() do
-    Chain.get_blocks_for_difficulty_calculation()
-    |> calculate_next_difficulty()
-  end
-
-  @spec calculate_next_difficulty :: integer()
+  @spec calculate_next_difficulty(list()) :: integer()
   def calculate_next_difficulty(list) do
     [latest_block | _] = list
 
diff --git a/apps/aecore/test/aecore_chain_test.exs b/apps/aecore/test/aecore_chain_test.exs
index c387739a..0517d395 100644
--- a/apps/aecore/test/aecore_chain_test.exs
+++ b/apps/aecore/test/aecore_chain_test.exs
@@ -11,6 +11,7 @@ defmodule AecoreChainTest do
   alias Aecore.Utils.Blockchain.BlockValidation
   alias Aecore.Chain.Worker, as: Chain
   alias Aecore.Miner.Worker, as: Miner
+  alias Aecore.Utils.Blockchain.Difficulty
 
   setup do
     Chain.start_link([])
@@ -32,21 +33,27 @@ defmodule AecoreChainTest do
 
     block = %Block{header: %Header{height: latest_block.header.height + 1,
                                    prev_hash: latest_block_hash,
-                                   txs_hash: <<0::256>>,chain_state_hash: new_chain_state_hash,
+                                   txs_hash: <<0::256>>,
+                                   chain_state_hash: new_chain_state_hash,
                                    difficulty_target: 1, nonce: 0,
-                                   timestamp: System.system_time(:milliseconds), version: 1}, txs: []}
+                                   timestamp: System.system_time(:milliseconds),
+                                   version: 1}, txs: []}
     {:ok, nbh} = Aecore.Pow.Cuckoo.generate(block.header)
     block = %{block | header: nbh}
 
     latest_block = Chain.latest_block()
     latest_block_hash = BlockValidation.block_header_hash(latest_block.header)
+    blocks_for_difficulty_calculation = Chain.get_blocks(latest_block_hash,
+                                              Difficulty.get_number_of_blocks)
     latest_block_hash_hex = latest_block_hash |> Base.encode16()
     [latest_block | [previous_block | []]] = Chain.get_blocks(latest_block_hash, 2)
 
     assert latest_block == Chain.get_block_by_hex_hash(latest_block_hash_hex)
     assert previous_block.header.height + 1 == latest_block.header.height
-    assert BlockValidation.validate_block!(latest_block, previous_block, Chain.chain_state())
-    assert :ok = Chain.add_block(block)
+    assert BlockValidation.validate_block!(latest_block, previous_block,
+                                            Chain.chain_state(),
+                                            blocks_for_difficulty_calculation)
+    assert :ok = Chain.add_validated_block(block)
     assert latest_block = Chain.latest_block()
     assert latest_block.header.height == block.header.height
 
diff --git a/apps/aecore/test/aecore_hashcash_test.exs b/apps/aecore/test/aecore_hashcash_test.exs
index 2eab6f99..5a7b2760 100644
--- a/apps/aecore/test/aecore_hashcash_test.exs
+++ b/apps/aecore/test/aecore_hashcash_test.exs
@@ -2,9 +2,9 @@ defmodule HashcashTest do
   use ExUnit.Case
   doctest Aecore.Pow.Hashcash
 
-  alias Aecore.Pow.Hashcash
-  alias Aecore.Structures.Header
-  alias Aecore.Structures.Block
+  # alias Aecore.Pow.Hashcash
+  # alias Aecore.Structures.Header
+  # alias Aecore.Structures.Block
 
   #@tag timeout: 10000000
   #test "successfull test" do
diff --git a/apps/aecore/test/aecore_validation_test.exs b/apps/aecore/test/aecore_validation_test.exs
index bd93bd67..02e509f1 100644
--- a/apps/aecore/test/aecore_validation_test.exs
+++ b/apps/aecore/test/aecore_validation_test.exs
@@ -49,7 +49,9 @@ defmodule AecoreValidationTest do
       txs_hash: <<0::256>>,
       version: 1},
       txs: []}
-    assert BlockValidation.validate_block!(new_block,prev_block, %{}) == :ok
+    blocks_for_difficulty_calculation = [new_block, prev_block]
+    assert BlockValidation.validate_block!(new_block, prev_block, %{}, 
+                                    blocks_for_difficulty_calculation) == :ok
   end
 
   test "validate transactions in a block" do
diff --git a/apps/aehttpserver/web/controllers/block_controller.ex b/apps/aehttpserver/web/controllers/block_controller.ex
index e58dafdc..143c4994 100644
--- a/apps/aehttpserver/web/controllers/block_controller.ex
+++ b/apps/aehttpserver/web/controllers/block_controller.ex
@@ -23,7 +23,7 @@ defmodule Aehttpserver.BlockController do
 
     block = Aecore.Utils.Serialization.block(map, :deserialize)
 
-    Aecore.Chain.Worker.add_block(block)
+    Aecore.Chain.Worker.add_validated_block(block)
     json conn, %{ok: "new block received"}
   end
 end

From 62192881148542d13847d71efe8d7ecbc4cb5cf3 Mon Sep 17 00:00:00 2001
From: Nedelcho Delchev <nedelcho_delchev@abv.bg>
Date: Tue, 21 Nov 2017 11:40:05 +0200
Subject: [PATCH 2/4] Fixed message display and function names

---
 README.md                                     | 24 +++++++++----------
 apps/aecore/lib/aecore/chain/worker.ex        | 14 +++++------
 apps/aecore/lib/aecore/miner/worker.ex        |  6 ++---
 apps/aecore/test/aecore_chain_test.exs        |  2 +-
 .../web/controllers/block_controller.ex       |  2 +-
 5 files changed, 24 insertions(+), 24 deletions(-)

diff --git a/README.md b/README.md
index 0645930e..1b1f19e4 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@
 
 # **Elixir blockchain research**
 
-This is an elixir implementation of a basic blockchain. We aim to keep the blockchain as simple as possible and to research and experiment with different technologies 
+This is an elixir implementation of a basic blockchain. We aim to keep the blockchain as simple as possible and to research and experiment with different technologies
 
 ## Getting Started
 
@@ -10,7 +10,7 @@ These instructions will get you a copy of the project up and running on your loc
 
 ## Prerequisites
 
-To install and use the Elixir Blockchain you will need [Elixir](https://elixir-lang.org/install.html) and the source code by cloning or downloading the repository. 
+To install and use the Elixir Blockchain you will need [Elixir](https://elixir-lang.org/install.html) and the source code by cloning or downloading the repository.
 
 ## Usage
 #### **Starting the application**
@@ -19,29 +19,29 @@ Start the application in interactive Elixir mode
 `iex -S mix phx.server`
 
 #### **Starting the miner**
-To start the miner use the following command in the command prompt: 
+To start the miner use the following command in the command prompt:
 
 `Aecore.Miner.Worker.resume()`
 
 This will continuously mine new blocks until terminated or suspended.
-To suspend/stop the miner from mining: 
+To suspend/stop the miner from mining:
 
 `Aecore.Miner.Worker.suspend() `
 
 #### **API calls**
-To add a block to the blockchain: 
+To add a block to the blockchain:
 
 `Aecore.Chain.Worker.add_block(%Block{}) :: :ok`
 
-To get all blocks in the current chain: 
+To get all blocks in the current chain:
 
 `Aecore.Chain.Worker.all_blocks() :: list()`
 
-To get the latest block added to the chain: 
+To get the latest block added to the chain:
 
 `Aecore.Chain.Worker.latest_block() :: %Block{}`
 
-To get the latest chainstate: 
+To get the latest chainstate:
 
 `Aecore.Chain.Worker.chain_state() :: map()`
 
@@ -49,11 +49,11 @@ To add a transaction to the Transaction Pool:
 
 `Aecore.Txs.Pool.Worker.add_transaction(%SignedTx{}) :: :ok | :error`
 
-To remove a transaction from the Transaction Pool: 
+To remove a transaction from the Transaction Pool:
 
 `Aecore.Txs.Pool.Worker.remove_transaction(%SignedTx{}) :: :ok | :error`
 
-To inspect all transactions in the Transaction Pool: 
+To inspect all transactions in the Transaction Pool:
 
 `Aecore.Txs.Pool.Worker.get_pool() :: map() `
 
@@ -63,9 +63,9 @@ To run the automatic tests:
 
 `mix test`
 
-## Logging 
+## Logging
 
-To debug, see errors, warnings and info about the blockchain, 
+To debug, see errors, warnings and info about the blockchain,
 the log can be found in the source folder under:`apps/aecore/logs`
 
 `09:59:16.298 [info] Added block #1 with hash 6C449AC3B5E38857DC85310873979F45992270BF54304B3F60BE4F64373991B5, total tokens: 100 `
diff --git a/apps/aecore/lib/aecore/chain/worker.ex b/apps/aecore/lib/aecore/chain/worker.ex
index 7a9bdf5f..c73cb823 100644
--- a/apps/aecore/lib/aecore/chain/worker.ex
+++ b/apps/aecore/lib/aecore/chain/worker.ex
@@ -68,8 +68,8 @@ defmodule Aecore.Chain.Worker do
     Enum.reverse(get_blocks([], start_block_hash, size))
   end
 
-  @spec add_validated_block(%Block{}) :: :ok
-  def add_validated_block(%Block{} = block) do
+  @spec add_block(%Block{}) :: :ok
+  def add_block(%Block{} = block) do
     latest_block = latest_block()
 
     prev_block_chain_state = chain_state()
@@ -80,12 +80,12 @@ defmodule Aecore.Chain.Worker do
     blocks_for_difficulty_calculation = get_blocks(latest_header_hash, Difficulty.get_number_of_blocks())
 
     BlockValidation.validate_block!(block, latest_block, new_chain_state, blocks_for_difficulty_calculation)
-    add_block(block)
+    add_validated_block(block)
   end
 
-  @spec add_block(%Block{}) :: :ok
-  defp add_block(%Block{} = block) do
-    GenServer.call(__MODULE__, {:add_block, block})
+  @spec add_validated_block(%Block{}) :: :ok
+  defp add_validated_block(%Block{} = block) do
+    GenServer.call(__MODULE__, {:add_validated_block, block})
   end
 
   @spec chain_state(binary()) :: map()
@@ -143,7 +143,7 @@ defmodule Aecore.Chain.Worker do
     end
   end
 
-  def handle_call({:add_block, %Block{} = block}, _from, state) do
+  def handle_call({:add_validated_block, %Block{} = block}, _from, state) do
     {block_map, latest_block_chain_state, txs_index} = state
     prev_block_chain_state = latest_block_chain_state[block.header.prev_hash]
     new_block_state = ChainState.calculate_block_state(block.txs)
diff --git a/apps/aecore/lib/aecore/miner/worker.ex b/apps/aecore/lib/aecore/miner/worker.ex
index 3ff7a3a6..e0bbe80e 100644
--- a/apps/aecore/lib/aecore/miner/worker.ex
+++ b/apps/aecore/lib/aecore/miner/worker.ex
@@ -142,9 +142,9 @@ defmodule Aecore.Miner.Worker do
       BlockValidation.validate_block!(latest_block, previous_block, chain_state, blocks_for_difficulty_calculation)
 
     catch
-      {:error, _message} ->
+      {:error, message} ->
         Logger.error(fn ->
-          "Failed to mine block"
+          "Failed to mine block: #{message}"
         end)
     end
 
@@ -180,7 +180,7 @@ defmodule Aecore.Miner.Worker do
           Logger.info(fn ->
             "Mined block ##{block.header.height}, difficulty target #{block.header.difficulty_target}, nonce #{block.header.nonce}"
             end)
-          Chain.add_validated_block(block)
+          Chain.add_block(block)
           {:block_found, 0}
 
         {:error, _message} ->
diff --git a/apps/aecore/test/aecore_chain_test.exs b/apps/aecore/test/aecore_chain_test.exs
index 0517d395..c5a48572 100644
--- a/apps/aecore/test/aecore_chain_test.exs
+++ b/apps/aecore/test/aecore_chain_test.exs
@@ -53,7 +53,7 @@ defmodule AecoreChainTest do
     assert BlockValidation.validate_block!(latest_block, previous_block,
                                             Chain.chain_state(),
                                             blocks_for_difficulty_calculation)
-    assert :ok = Chain.add_validated_block(block)
+    assert :ok = Chain.add_block(block)
     assert latest_block = Chain.latest_block()
     assert latest_block.header.height == block.header.height
 
diff --git a/apps/aehttpserver/web/controllers/block_controller.ex b/apps/aehttpserver/web/controllers/block_controller.ex
index 143c4994..e58dafdc 100644
--- a/apps/aehttpserver/web/controllers/block_controller.ex
+++ b/apps/aehttpserver/web/controllers/block_controller.ex
@@ -23,7 +23,7 @@ defmodule Aehttpserver.BlockController do
 
     block = Aecore.Utils.Serialization.block(map, :deserialize)
 
-    Aecore.Chain.Worker.add_validated_block(block)
+    Aecore.Chain.Worker.add_block(block)
     json conn, %{ok: "new block received"}
   end
 end

From 101f2a462a9085f0dbdc2dbe4a063418ea4d0929 Mon Sep 17 00:00:00 2001
From: Nedelcho Delchev <nedelcho_delchev@abv.bg>
Date: Tue, 21 Nov 2017 14:49:28 +0200
Subject: [PATCH 3/4] Different approach for getting blocks in add_block

---
 apps/aecore/lib/aecore/chain/worker.ex                    | 8 +++++++-
 .../lib/aecore/utils/blockchain/block_validation.ex       | 3 +++
 apps/aecore/lib/aecore/utils/blockchain/difficulty.ex     | 2 +-
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/apps/aecore/lib/aecore/chain/worker.ex b/apps/aecore/lib/aecore/chain/worker.ex
index c73cb823..7d1b4827 100644
--- a/apps/aecore/lib/aecore/chain/worker.ex
+++ b/apps/aecore/lib/aecore/chain/worker.ex
@@ -77,7 +77,13 @@ defmodule Aecore.Chain.Worker do
     new_chain_state = ChainState.calculate_chain_state(new_block_state, prev_block_chain_state)
 
     latest_header_hash = BlockValidation.block_header_hash(latest_block.header)
-    blocks_for_difficulty_calculation = get_blocks(latest_header_hash, Difficulty.get_number_of_blocks())
+
+    blocks_for_difficulty_calculation = if(block.header.height == 1) do
+      get_blocks(latest_header_hash, Difficulty.get_number_of_blocks())
+    else
+      something = get_blocks(latest_header_hash, Difficulty.get_number_of_blocks())
+      [block | something] |> Enum.take(Difficulty.get_number_of_blocks())
+    end
 
     BlockValidation.validate_block!(block, latest_block, new_chain_state, blocks_for_difficulty_calculation)
     add_validated_block(block)
diff --git a/apps/aecore/lib/aecore/utils/blockchain/block_validation.ex b/apps/aecore/lib/aecore/utils/blockchain/block_validation.ex
index 0f842cec..4807a3ba 100644
--- a/apps/aecore/lib/aecore/utils/blockchain/block_validation.ex
+++ b/apps/aecore/lib/aecore/utils/blockchain/block_validation.ex
@@ -20,6 +20,9 @@ defmodule Aecore.Utils.Blockchain.BlockValidation do
     coinbase_transactions_sum = sum_coinbase_transactions(new_block)
     total_fees = Miner.calculate_total_fees(new_block.txs)
 
+    heights = Enum.map(blocks_for_difficulty_calculation, fn(block) -> block.header.height end)
+    IO.inspect(heights)
+
     difficulty = Difficulty.calculate_next_difficulty(blocks_for_difficulty_calculation)
 
     cond do
diff --git a/apps/aecore/lib/aecore/utils/blockchain/difficulty.ex b/apps/aecore/lib/aecore/utils/blockchain/difficulty.ex
index 197c3569..9211fce9 100644
--- a/apps/aecore/lib/aecore/utils/blockchain/difficulty.ex
+++ b/apps/aecore/lib/aecore/utils/blockchain/difficulty.ex
@@ -1,6 +1,6 @@
 defmodule Aecore.Utils.Blockchain.Difficulty do
 
-  @number_of_blocks 100
+  @number_of_blocks 3
   @max_difficulty_change 2
   @target_distance 60000
 

From ba6d1e57db339022a02124c85deb72d8c0bd8570 Mon Sep 17 00:00:00 2001
From: Philipp Piwo <github@piwo.space>
Date: Tue, 21 Nov 2017 15:36:52 +0200
Subject: [PATCH 4/4] [GH-#85] resolved issue with difficulty validation  - do
 correct check in miner, differing from next calculation

---
 apps/aecore/lib/aecore/chain/worker.ex        | 11 +--
 apps/aecore/lib/aecore/miner/worker.ex        | 78 +++++++++++++------
 apps/aecore/lib/aecore/peers/sync.ex          |  1 -
 .../utils/blockchain/block_validation.ex      |  4 -
 .../lib/aecore/utils/blockchain/difficulty.ex |  2 +-
 5 files changed, 56 insertions(+), 40 deletions(-)

diff --git a/apps/aecore/lib/aecore/chain/worker.ex b/apps/aecore/lib/aecore/chain/worker.ex
index 7d1b4827..bb4cf001 100644
--- a/apps/aecore/lib/aecore/chain/worker.ex
+++ b/apps/aecore/lib/aecore/chain/worker.ex
@@ -78,13 +78,7 @@ defmodule Aecore.Chain.Worker do
 
     latest_header_hash = BlockValidation.block_header_hash(latest_block.header)
 
-    blocks_for_difficulty_calculation = if(block.header.height == 1) do
-      get_blocks(latest_header_hash, Difficulty.get_number_of_blocks())
-    else
-      something = get_blocks(latest_header_hash, Difficulty.get_number_of_blocks())
-      [block | something] |> Enum.take(Difficulty.get_number_of_blocks())
-    end
-
+    blocks_for_difficulty_calculation = get_blocks(latest_header_hash, Difficulty.get_number_of_blocks())
     BlockValidation.validate_block!(block, latest_block, new_chain_state, blocks_for_difficulty_calculation)
     add_validated_block(block)
   end
@@ -153,8 +147,7 @@ defmodule Aecore.Chain.Worker do
     {block_map, latest_block_chain_state, txs_index} = state
     prev_block_chain_state = latest_block_chain_state[block.header.prev_hash]
     new_block_state = ChainState.calculate_block_state(block.txs)
-    new_chain_state =
-      ChainState.calculate_chain_state(new_block_state, prev_block_chain_state)
+    new_chain_state = ChainState.calculate_chain_state(new_block_state, prev_block_chain_state)
 
     new_block_txs_index = calculate_block_acc_txs_info(block)
     new_txs_index = update_txs_index(txs_index, new_block_txs_index)
diff --git a/apps/aecore/lib/aecore/miner/worker.ex b/apps/aecore/lib/aecore/miner/worker.ex
index e0bbe80e..9064b1ab 100644
--- a/apps/aecore/lib/aecore/miner/worker.ex
+++ b/apps/aecore/lib/aecore/miner/worker.ex
@@ -74,9 +74,15 @@ defmodule Aecore.Miner.Worker do
 
   ## Running ##
   def running(:cast, :mine, start_nonce) do
-    {_, next_nonce} = mine_next_block(start_nonce)
-    GenStateMachine.cast(__MODULE__, :mine)
-    {:next_state, :running, next_nonce}
+    {status, next_nonce} = mine_next_block(start_nonce)
+    case status do
+      :error ->
+        Logger.info("Mining stopped by error")
+        {:next_state, :idle, 0}
+      _ ->
+        GenStateMachine.cast(__MODULE__, :mine)
+        {:next_state, :running, next_nonce}
+    end
   end
 
   def running({:call, from}, :get_state, _data) do
@@ -88,7 +94,7 @@ defmodule Aecore.Miner.Worker do
   end
 
   def running({:call, from}, :suspend, data) do
-    Logger.info("Mined stopped by user")
+    Logger.info("Mining stopped by user")
     {:next_state, :idle, data, [{:reply, from, :ok}]}
   end
 
@@ -115,9 +121,13 @@ defmodule Aecore.Miner.Worker do
   def coinbase_transaction_value, do: @coinbase_transaction_value
 
   def calculate_total_fees(txs) do
-    List.foldl(txs, 0, fn(tx, acc) ->
+    List.foldl(
+      txs,
+      0,
+      fn (tx, acc) ->
         acc + tx.data.fee
-      end)
+      end
+    )
   end
 
   ## Internal
@@ -127,31 +137,37 @@ defmodule Aecore.Miner.Worker do
     latest_block_hash = BlockValidation.block_header_hash(latest_block.header)
     chain_state = Chain.chain_state(latest_block_hash)
 
-    txs_list = Map.values(Pool.get_pool())
-    ordered_txs_list = Enum.sort(txs_list, fn(tx1, tx2) -> tx1.data.nonce < tx2.data.nonce end)
+    blocks_for_difficulty_validation = if(latest_block.header.height == 0) do
+      Chain.get_blocks(latest_block_hash, Difficulty.get_number_of_blocks())
+    else
+      [_ | something] = Chain.get_blocks(latest_block_hash, Difficulty.get_number_of_blocks() + 1)
+      something
+    end
 
-    blocks_for_difficulty_calculation = Chain.get_blocks(latest_block_hash, Difficulty.get_number_of_blocks())
     previous_block = cond do
       latest_block == Block.genesis_block() -> nil
       true ->
         blocks = Chain.get_blocks(latest_block_hash, 2)
         Enum.at(blocks, 1)
     end
-    try do
-
-      BlockValidation.validate_block!(latest_block, previous_block, chain_state, blocks_for_difficulty_calculation)
-
-    catch
-      {:error, message} ->
-        Logger.error(fn ->
-          "Failed to mine block: #{message}"
-        end)
-    end
 
+    try do
+      BlockValidation.validate_block!(
+        latest_block,
+        previous_block,
+        chain_state,
+        blocks_for_difficulty_validation
+      )
+
+      blocks_for_difficulty_calculation = Chain.get_blocks(latest_block_hash, Difficulty.get_number_of_blocks())
       difficulty = Difficulty.calculate_next_difficulty(blocks_for_difficulty_calculation)
 
+      txs_list = Map.values(Pool.get_pool())
+      ordered_txs_list = Enum.sort(txs_list, fn (tx1, tx2) -> tx1.data.nonce < tx2.data.nonce end)
       valid_txs = BlockValidation.filter_invalid_transactions_chainstate(ordered_txs_list, chain_state)
+
       {_, pubkey} = Keys.pubkey()
+
       total_fees = calculate_total_fees(valid_txs)
       valid_txs = [get_coinbase_transaction(pubkey, total_fees) | valid_txs]
       root_hash = BlockValidation.calculate_root_hash(valid_txs)
@@ -169,22 +185,34 @@ defmodule Aecore.Miner.Worker do
           root_hash,
           chain_state_hash,
           difficulty,
-          0, #start from nonce 0, will be incremented in mining
+          0,
+          #start from nonce 0, will be incremented in mining
           Block.current_block_version()
         )
+
       Logger.debug("start nonce #{start_nonce}. Final nonce = #{start_nonce + @nonce_per_cycle}")
-      case Cuckoo.generate(%{unmined_header
-                             | nonce: start_nonce + @nonce_per_cycle}) do
+
+      case Cuckoo.generate(%{unmined_header | nonce: start_nonce + @nonce_per_cycle}) do
         {:ok, mined_header} ->
           block = %Block{header: mined_header, txs: valid_txs}
-          Logger.info(fn ->
-            "Mined block ##{block.header.height}, difficulty target #{block.header.difficulty_target}, nonce #{block.header.nonce}"
-            end)
+          Logger.info(
+            fn ->
+              "Mined block ##{block.header.height}, difficulty target #{block.header.difficulty_target}, nonce #{
+                block.header.nonce
+              }" end
+          )
           Chain.add_block(block)
           {:block_found, 0}
 
         {:error, _message} ->
           {:no_block_found, start_nonce + @nonce_per_cycle}
       end
+
+    catch
+      message ->
+        Logger.error(fn -> "Failed to mine block: #{Kernel.inspect(message)}" end)
+        {:error, message}
+    end
+
   end
 end
diff --git a/apps/aecore/lib/aecore/peers/sync.ex b/apps/aecore/lib/aecore/peers/sync.ex
index e2463a50..e1064484 100644
--- a/apps/aecore/lib/aecore/peers/sync.ex
+++ b/apps/aecore/lib/aecore/peers/sync.ex
@@ -62,7 +62,6 @@ defmodule Aecore.Peers.Sync do
     peers_count = map_size(Peers.all_peers())
     cond do
       peers_count == 0 ->
-        Logger.error(fn -> "No peers" end)
         {:error, "No peers"}
       peers_count < @peers_target_count ->
         all_peers = Map.keys(Peers.all_peers())
diff --git a/apps/aecore/lib/aecore/utils/blockchain/block_validation.ex b/apps/aecore/lib/aecore/utils/blockchain/block_validation.ex
index 4807a3ba..dd7eda4b 100644
--- a/apps/aecore/lib/aecore/utils/blockchain/block_validation.ex
+++ b/apps/aecore/lib/aecore/utils/blockchain/block_validation.ex
@@ -19,10 +19,6 @@ defmodule Aecore.Utils.Blockchain.BlockValidation do
     is_difficulty_target_met = Cuckoo.verify(new_block.header)
     coinbase_transactions_sum = sum_coinbase_transactions(new_block)
     total_fees = Miner.calculate_total_fees(new_block.txs)
-
-    heights = Enum.map(blocks_for_difficulty_calculation, fn(block) -> block.header.height end)
-    IO.inspect(heights)
-
     difficulty = Difficulty.calculate_next_difficulty(blocks_for_difficulty_calculation)
 
     cond do
diff --git a/apps/aecore/lib/aecore/utils/blockchain/difficulty.ex b/apps/aecore/lib/aecore/utils/blockchain/difficulty.ex
index 9211fce9..197c3569 100644
--- a/apps/aecore/lib/aecore/utils/blockchain/difficulty.ex
+++ b/apps/aecore/lib/aecore/utils/blockchain/difficulty.ex
@@ -1,6 +1,6 @@
 defmodule Aecore.Utils.Blockchain.Difficulty do
 
-  @number_of_blocks 3
+  @number_of_blocks 100
   @max_difficulty_change 2
   @target_distance 60000