diff --git a/CHANGELOG.md b/CHANGELOG.md
index dbc3bce..bc55e6d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -17,6 +17,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - when verifier proposing, `Chain` checks, if verifier is active instead
   of if it is only created.
 - split Chain contract into two separate contracts (storage and manager)
+- Flexible duration of election phases
 
 ## [0.3.0] - 2018-12-13
 ### Added:
diff --git a/contracts/Chain.sol b/contracts/Chain.sol
index 349da37..6522fb9 100644
--- a/contracts/Chain.sol
+++ b/contracts/Chain.sol
@@ -20,11 +20,11 @@ contract Chain is IChain, RegistrableWithSingleStorage, ReentrancyGuard, Ownable
   bytes32  constant NAME = "Chain";
 
   modifier whenProposePhase() {
-    require(getCurrentElectionCycleBlock() < blocksPerPhase(), "we are not in propose phase");
+    require(getCurrentElectionCycleBlock() < blocksPerPropose(), "we are not in propose phase");
     _;
   }
   modifier whenRevealPhase() {
-    require(getCurrentElectionCycleBlock() >= blocksPerPhase(), "we are not in reveal phase");
+    require(getCurrentElectionCycleBlock() >= blocksPerPropose(), "we are not in reveal phase");
     _;
   }
 
@@ -113,7 +113,7 @@ contract Chain is IChain, RegistrableWithSingleStorage, ReentrancyGuard, Ownable
   }
 
   function getBlockHeight() public view returns (uint256) {
-    return block.number.div(uint256(blocksPerPhase()) * 2);
+    return block.number.div(uint256(blocksPerElection()));
   }
 
   /// @dev this function needs to be called each time we successfully reveal a proposal
@@ -214,6 +214,10 @@ contract Chain is IChain, RegistrableWithSingleStorage, ReentrancyGuard, Ownable
     _storage().setInitialBlockHeight(_shard, _blockHeight);
   }
 
+  function updatePhasesDurations(uint8 _blocksPerPropose, uint8 _blocksPerReveal) external onlyOwner {
+    _storage().updatePhasesDurations(_blocksPerPropose, _blocksPerReveal);
+  }
+
   function updateMinimumStakingTokenPercentage(uint8 _minimumStakingTokenPercentage)
   public
   onlyOwner
@@ -235,18 +239,32 @@ contract Chain is IChain, RegistrableWithSingleStorage, ReentrancyGuard, Ownable
     return _storage().minimumStakingTokenPercentage();
   }
 
-  function blocksPerPhase()
+  function blocksPerPropose()
+  public
+  view
+  returns (uint8) {
+    return _storage().blocksPerPropose();
+  }
+
+  function blocksPerReveal()
+  public
+  view
+  returns (uint8) {
+    return _storage().blocksPerReveal();
+  }
+
+  function blocksPerElection()
   public
   view
   returns (uint8) {
-    return _storage().blocksPerPhase();
+    return _storage().blocksPerPropose() + _storage().blocksPerReveal();
   }
 
   function getCurrentElectionCycleBlock()
   public
   view
   returns (uint256) {
-    return block.number % (uint256(blocksPerPhase()) * 2);
+    return block.number % uint256(blocksPerElection());
   }
 
   /// @return first block number (blockchain block) of current cycle
@@ -261,7 +279,7 @@ contract Chain is IChain, RegistrableWithSingleStorage, ReentrancyGuard, Ownable
   public
   view
   returns (bool) {
-    return getCurrentElectionCycleBlock() < blocksPerPhase();
+    return getCurrentElectionCycleBlock() < blocksPerPropose();
   }
 
   function initialBlockHeights(uint256 _shard)
diff --git a/contracts/ChainStorage.sol b/contracts/ChainStorage.sol
index a69ab1a..19ba983 100644
--- a/contracts/ChainStorage.sol
+++ b/contracts/ChainStorage.sol
@@ -46,17 +46,28 @@ contract ChainStorage is StorageBase {
 
   bool public updateMinimumStakingTokenPercentageEnabled;
 
-  uint8 public blocksPerPhase;
+  uint8 public blocksPerPropose;
+  uint8 public blocksPerReveal;
 
   uint8 public minimumStakingTokenPercentage;
 
-  event LogChainConfig(uint8 blocksPerPhase, uint8 requirePercentOfTokens, bool updateMinimumStakingTokenPercentageEnabled);
+  event LogChainConfig(
+    uint8 blocksPerPropose,
+    uint8 blocksPerReveal,
+    uint8 requirePercentOfTokens,
+    bool updateMinimumStakingTokenPercentageEnabled
+  );
 
-  constructor(uint8 _blocksPerPhase,
+  constructor(
+    uint8 _blocksPerPropose,
+    uint8 _blocksPerReveal,
     uint8 _minimumStakingTokenPercentage,
     bool _updateMinimumStakingTokenPercentageEnabled) public {
-    require(_blocksPerPhase > 0, "_blocksPerPhase can't be empty");
-    blocksPerPhase = _blocksPerPhase;
+    require(_blocksPerPropose > 0, "_blocksPerPhase can't be empty");
+    require(_blocksPerReveal > 0, "_blocksPerReveal can't be empty");
+
+    blocksPerPropose = _blocksPerPropose;
+    blocksPerReveal = _blocksPerReveal;
 
     require(_minimumStakingTokenPercentage > 0, "_minimumStakingTokenPercentage can't be empty");
     require(_minimumStakingTokenPercentage <= 100, "_minimumStakingTokenPercentage can't be over 100%");
@@ -64,7 +75,12 @@ contract ChainStorage is StorageBase {
 
     updateMinimumStakingTokenPercentageEnabled = _updateMinimumStakingTokenPercentageEnabled;
 
-    emit LogChainConfig(_blocksPerPhase, _minimumStakingTokenPercentage, _updateMinimumStakingTokenPercentageEnabled);
+    emit LogChainConfig(
+      _blocksPerPropose,
+      _blocksPerReveal,
+      _minimumStakingTokenPercentage,
+      _updateMinimumStakingTokenPercentageEnabled
+    );
   }
 
   function getInitialBlockHeight(uint256 _shard) public view returns (uint256) {
@@ -160,6 +176,22 @@ contract ChainStorage is StorageBase {
     return true;
   }
 
+  function updatePhasesDurations(uint8 _blocksPerPropose, uint8 _blocksPerReveal)
+  external
+  onlyFromStorageOwner
+  returns (bool) {
+    require(_blocksPerPropose > 0, "_blocksPerPropose can't be empty");
+    require(_blocksPerReveal > 0, "_blocksPerReveal can't be empty");
+    require(blocksPerPropose + blocksPerReveal == _blocksPerPropose + _blocksPerReveal, "election duration must be fixed");
+
+    blocksPerPropose = _blocksPerPropose;
+    blocksPerReveal = _blocksPerReveal;
+
+    emit LogChainConfig(blocksPerPropose, blocksPerReveal, minimumStakingTokenPercentage, true);
+
+    return true;
+  }
+
   function updateMinimumStakingTokenPercentage(uint8 _minimumStakingTokenPercentage)
   external
   onlyFromStorageOwner
@@ -170,7 +202,7 @@ contract ChainStorage is StorageBase {
     require(_minimumStakingTokenPercentage <= 100, "_minimumStakingTokenPercentage can't be over 100%");
     minimumStakingTokenPercentage = _minimumStakingTokenPercentage;
 
-    emit LogChainConfig(blocksPerPhase, _minimumStakingTokenPercentage, true);
+    emit LogChainConfig(blocksPerPropose, blocksPerReveal, _minimumStakingTokenPercentage, true);
 
     return true;
   }