diff --git a/blockchain.js b/blockchain.js
index a5fa42d..cc16973 100644
--- a/blockchain.js
+++ b/blockchain.js
@@ -1,4 +1,5 @@
 const Block = require('./block');
+const cryptoHash = require('./crypto-hash');
 
 class Blockchain {
   constructor() {
@@ -13,6 +14,24 @@ class Blockchain {
 
     this.chain.push(newBlock);
   }
+
+  static isValidChain(chain) {
+    if(JSON.stringify(chain[0]) !== JSON.stringify(Block.genesis())) return false;
+
+    for (let i=1; i<chain.length; i++) {
+      const { timestamp, lastHash, hash, data } = chain[i];
+
+      const actualLastHash = chain[i-1].hash;
+
+      if (lastHash !== actualLastHash) return false;
+
+      const validatedHash = cryptoHash(timestamp, lastHash, data);
+
+      if (hash !== validatedHash) return false;
+    }
+
+    return true;
+  }
 }
 
 module.exports = Blockchain;