diff --git a/Blockchain.xcodeproj/project.pbxproj b/Blockchain.xcodeproj/project.pbxproj
index ec86c69..b3ae72c 100644
--- a/Blockchain.xcodeproj/project.pbxproj
+++ b/Blockchain.xcodeproj/project.pbxproj
@@ -8,6 +8,8 @@
 
 /* Begin PBXBuildFile section */
 		B5E66EBD2407FDE000E89D17 /* main.swift in Sources */ = {isa = PBXBuildFile; fileRef = B5E66EBC2407FDE000E89D17 /* main.swift */; };
+		B5E66EC52407FE0900E89D17 /* Block.swift in Sources */ = {isa = PBXBuildFile; fileRef = B5E66EC42407FE0900E89D17 /* Block.swift */; };
+		B5E66EC72407FEC800E89D17 /* Blockchain.swift in Sources */ = {isa = PBXBuildFile; fileRef = B5E66EC62407FEC800E89D17 /* Blockchain.swift */; };
 /* End PBXBuildFile section */
 
 /* Begin PBXCopyFilesBuildPhase section */
@@ -25,6 +27,8 @@
 /* Begin PBXFileReference section */
 		B5E66EB92407FDE000E89D17 /* Blockchain */ = {isa = PBXFileReference; explicitFileType = "compiled.mach-o.executable"; includeInIndex = 0; path = Blockchain; sourceTree = BUILT_PRODUCTS_DIR; };
 		B5E66EBC2407FDE000E89D17 /* main.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = main.swift; sourceTree = "<group>"; };
+		B5E66EC42407FE0900E89D17 /* Block.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Block.swift; sourceTree = "<group>"; };
+		B5E66EC62407FEC800E89D17 /* Blockchain.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Blockchain.swift; sourceTree = "<group>"; };
 /* End PBXFileReference section */
 
 /* Begin PBXFrameworksBuildPhase section */
@@ -57,11 +61,21 @@
 		B5E66EBB2407FDE000E89D17 /* Blockchain */ = {
 			isa = PBXGroup;
 			children = (
+				B5E66EC32407FDEC00E89D17 /* Models */,
 				B5E66EBC2407FDE000E89D17 /* main.swift */,
 			);
 			path = Blockchain;
 			sourceTree = "<group>";
 		};
+		B5E66EC32407FDEC00E89D17 /* Models */ = {
+			isa = PBXGroup;
+			children = (
+				B5E66EC42407FE0900E89D17 /* Block.swift */,
+				B5E66EC62407FEC800E89D17 /* Blockchain.swift */,
+			);
+			path = Models;
+			sourceTree = "<group>";
+		};
 /* End PBXGroup section */
 
 /* Begin PBXNativeTarget section */
@@ -121,6 +135,8 @@
 			buildActionMask = 2147483647;
 			files = (
 				B5E66EBD2407FDE000E89D17 /* main.swift in Sources */,
+				B5E66EC52407FE0900E89D17 /* Block.swift in Sources */,
+				B5E66EC72407FEC800E89D17 /* Blockchain.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
diff --git a/Blockchain.xcodeproj/xcuserdata/vbodinaud.xcuserdatad/xcdebugger/Breakpoints_v2.xcbkptlist b/Blockchain.xcodeproj/xcuserdata/vbodinaud.xcuserdatad/xcdebugger/Breakpoints_v2.xcbkptlist
new file mode 100644
index 0000000..27d5527
--- /dev/null
+++ b/Blockchain.xcodeproj/xcuserdata/vbodinaud.xcuserdatad/xcdebugger/Breakpoints_v2.xcbkptlist
@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Bucket
+   uuid = "1409866F-116F-4CB0-A121-C7CA467135B7"
+   type = "1"
+   version = "2.0">
+</Bucket>
diff --git a/Blockchain/Models/Block.swift b/Blockchain/Models/Block.swift
new file mode 100644
index 0000000..4573654
--- /dev/null
+++ b/Blockchain/Models/Block.swift
@@ -0,0 +1,25 @@
+//
+//  Block.swift
+//  Blockchain
+//
+//  Created by Victor BODINAUD on 27/02/2020.
+//  Copyright © 2020 Victor BODINAUD. All rights reserved.
+//
+
+import Foundation
+import CryptoKit
+
+class Block {
+    var hash: String!
+    var data: String!
+    var previousHash: String!
+    var index: Int!
+    
+    func generateHash() -> String {
+        if let hashData = data.data(using: .utf8) {
+            _ = SHA256.hash(data: hashData)
+        }
+        
+        return NSUUID().uuidString.replacingOccurrences(of: "-", with: "")
+    }
+}
diff --git a/Blockchain/Models/Blockchain.swift b/Blockchain/Models/Blockchain.swift
new file mode 100644
index 0000000..d0ded70
--- /dev/null
+++ b/Blockchain/Models/Blockchain.swift
@@ -0,0 +1,34 @@
+//
+//  Blockchain.swift
+//  Blockchain
+//
+//  Created by Victor BODINAUD on 27/02/2020.
+//  Copyright © 2020 Victor BODINAUD. All rights reserved.
+//
+
+import Foundation
+
+class Blockchain {
+    var chain = [Block]()
+    
+    func createGenesisBlock(data: String) {
+        let genesisBlock = Block()
+        genesisBlock.data = data
+        genesisBlock.previousHash = "0000"
+        genesisBlock.index = 0
+        genesisBlock.hash = genesisBlock.generateHash()
+        chain.append(genesisBlock)
+        print("Genesis block created -- hash: \(genesisBlock.hash ?? "")")
+    }
+    
+    func createBlock(data: String) {
+        let newBlock = Block()
+        newBlock.data = data
+        newBlock.previousHash = chain[chain.count-1].hash
+        newBlock.index = chain.count
+        newBlock.hash = newBlock.generateHash()
+        chain.append(newBlock)
+        
+        print("Block \(newBlock.index ?? 0) created -- hash: \(newBlock.hash ?? "") previous hash: \(newBlock.previousHash ?? "") data: \(newBlock.data ?? "")")
+    }
+}
diff --git a/Blockchain/main.swift b/Blockchain/main.swift
index 6010d29..e0d7c02 100644
--- a/Blockchain/main.swift
+++ b/Blockchain/main.swift
@@ -8,5 +8,25 @@
 
 import Foundation
 
-print("Hello, World!")
+let blockchain = Blockchain()
+var command: String?
 
+blockchain.createGenesisBlock(data: "")
+
+repeat {
+    print("Enter command:")
+    command = readLine()
+    
+    if command == "create" {
+        print("data for the new block:")
+        let data = readLine()
+        blockchain.createBlock(data: data ?? "")
+    }
+    
+    if command == "spam" {
+        for _ in 1...1000000 {
+            blockchain.createBlock(data: "\((blockchain.chain.last?.index ?? 0)+1)")
+        }
+    }
+    
+} while command != "exit"