diff --git a/Block.cpp b/Block.cpp
index bc87640..c97bf23 100644
--- a/Block.cpp
+++ b/Block.cpp
@@ -5,8 +5,6 @@
 
 #include "Block.h"
 
-size_t Block::max_height = 0;
-
 void Block::calculateHash() {
     memset(hash, 0, SHA256_DIGEST_LENGTH);
     SHA256_CTX sha;
@@ -31,10 +29,27 @@ Block::Block(Transaction tr[], size_t count, const char *prev_hash) {
         memset(this->prev_hash, 0, SHA256_CBLOCK+1);
     else
         strcpy(this->prev_hash, prev_hash);
-    height = ++max_height;
     calculateHash();
 }
 
+void Block::mine(size_t diff) {
+    difficulty = diff;
+    std::string str;
+    for (int i = 0; i < diff; ++i) {
+        str += '0';
+    }
+
+    while(strncmp(hash,str.c_str(),diff) != 0){
+        nonce++;
+        calculateHash();
+        std::cout << nonce << std::endl;
+    }
+}
+
+size_t Block::getDifficulty() const {
+    return difficulty;
+}
+
 Transaction &Transaction::operator=(Transaction &tr) {
     if(this != &tr){
         strcpy(sender,tr.getSender());
diff --git a/Block.h b/Block.h
index 0c6ee41..8a18eac 100644
--- a/Block.h
+++ b/Block.h
@@ -49,14 +49,14 @@ class Block {
     char hash[SHA256_CBLOCK+1];
     char prev_hash[SHA256_CBLOCK+1];
     Transaction transactions[MAX_BLOCK_TRANSACTION];
-    size_t height;
-    static size_t max_height;
+    size_t difficulty;
+    int nonce = 0;
 public:
-    size_t getHeight() { return height; }
-    static size_t getMaxHeight() { return max_height; }
     char* getHash() const { return (char*)hash;}
     char* getPerviousHash() const { return (char*)prev_hash;}
+    size_t getDifficulty() const;
     Block(Transaction tr[],size_t count, const char *prev_hash = "");
+    void mine(size_t diff);
 private:
     void calculateHash();
 };
diff --git a/Blockchain.cpp b/Blockchain.cpp
index af52b03..bd736bc 100644
--- a/Blockchain.cpp
+++ b/Blockchain.cpp
@@ -34,3 +34,30 @@ bool Blockchain::addBlock(Block &b) {
     blockList.push_back(b);
     return verifyBlocks();
 }
+
+Block Blockchain::operator[](size_t id) {
+    if(id >= blockList.size())
+        throw std::out_of_range("Out of range");
+    return blockList[id];
+}
+
+bool Blockchain::operator<(Blockchain &b) {
+    return blockList.size() < b.blockList.size();
+}
+
+size_t Blockchain::getHeight() const {
+    return blockList.size();
+}
+
+bool Blockchain::operator>(Blockchain &b) {
+    return blockList.size() > b.getHeight();
+}
+
+Blockchain::Blockchain() {
+
+}
+
+Blockchain::Blockchain(const Blockchain &b) {
+    for(Block bl : b.blockList)
+        blockList.push_back(bl);
+}
diff --git a/Blockchain.h b/Blockchain.h
index bf0f47a..b86e2d2 100644
--- a/Blockchain.h
+++ b/Blockchain.h
@@ -15,11 +15,17 @@ class Blockchain {
     static int blockReward;
     std::vector<Block> blockList;
 public:
+    Blockchain();
+    Blockchain(const Blockchain &b);
     const std::vector<Block> &getBlockList() const;
     static int getDifficulty();
     static int getBlockReward();
     bool verifyBlocks() const;
+    size_t getHeight() const;
     bool addBlock(Block& b);
+    Block operator[](size_t id);
+    bool operator<(Blockchain& b);
+    bool operator>(Blockchain& b);
 };
 
 
diff --git a/main.cpp b/main.cpp
index 62eb1b6..8d4fc85 100644
--- a/main.cpp
+++ b/main.cpp
@@ -4,9 +4,10 @@
 
 int main() {
     std::cout << "Hello, World!" << std::endl;
-    Transaction tr("","Balazs",100);
+    Transaction tr("","Balazs1",100);
     Transaction trs[] = {tr};
     Block b(trs,1);
+    b.mine(3);
     std::cout << b.getHash() << std::endl;
     Block b2(nullptr,0,b.getHash());
     std::cout << b.getHash() << std::endl;