diff --git a/package.json b/package.json
index 38efd00..cbb8e01 100644
--- a/package.json
+++ b/package.json
@@ -38,7 +38,8 @@
   "homepage": "https://github.com/ipfs/js-ipfs-block#readme",
   "devDependencies": {
     "aegir": "^8.0.0",
-    "chai": "^3.5.0"
+    "chai": "^3.5.0",
+    "multihashes": "^0.2.2"
   },
   "dependencies": {
     "multihashing": "^0.2.0"
@@ -47,4 +48,4 @@
     "David Dias <daviddias.p@gmail.com>",
     "dignifiedquire <dignifiedquire@gmail.com>"
   ]
-}
\ No newline at end of file
+}
diff --git a/src/index.js b/src/index.js
index c3ce0f6..cbb6035 100644
--- a/src/index.js
+++ b/src/index.js
@@ -1,8 +1,8 @@
 'use strict'
-const util = require('./util')
 
-// Immutable block of data
-function Block (data, type) {
+const multihashing = require('multihashing')
+
+function Block (data) {
   if (!data) {
     throw new Error('Block must be constructed with data')
   }
@@ -17,21 +17,13 @@ function Block (data, type) {
     this.data = new Buffer(data)
   }
 
-  this.key = util.hash(this.data)
-  this.type = type || 'protobuf'
-}
-
-Object.defineProperty(Block.prototype, 'extension', {
-  get () {
-    switch (this.type) {
-      case 'protobuf':
-        return 'data'
-      case 'ipld':
-        return 'ipld'
-      default:
-        return this.type
+  this.key = (hashFunc) => {
+    if (!hashFunc) {
+      hashFunc = 'sha2-256'
     }
+
+    return multihashing(this.data, hashFunc)
   }
-})
+}
 
 module.exports = Block
diff --git a/src/util.js b/src/util.js
deleted file mode 100644
index c1c7c74..0000000
--- a/src/util.js
+++ /dev/null
@@ -1,8 +0,0 @@
-'use strict'
-
-const multihashing = require('multihashing')
-
-exports = module.exports
-
-// Hash is the global IPFS hash function. uses multihash SHA2_256, 256 bits
-exports.hash = (data) => multihashing(data, 'sha2-256')
diff --git a/test/block.spec.js b/test/block.spec.js
index f474e1c..50c548d 100644
--- a/test/block.spec.js
+++ b/test/block.spec.js
@@ -3,20 +3,21 @@
 
 const expect = require('chai').expect
 const Block = require('../src')
+const multihash = require('multihashes')
 
 describe('block', () => {
   it('create', () => {
     const b = new Block('random-data')
-    expect(b.key).to.exist
+    expect(multihash.toB58String(b.key())).to.equal('QmeoBGh5g5kHgK3xppJ1YPwB9xgH2GoqhMSuQVpzDdvtJG')
+    expect(multihash.toB58String(b.key('sha1'))).to.equal('5dsvLgRV9RVj9eSgtxMrXQjbpfFeHY')
     expect(b.data).to.exist
-    expect(b.extension).to.be.eql('data')
   })
 
   it('create /wo new', () => {
     const b = Block('random-data')
-    expect(b.key).to.exist
+    expect(multihash.toB58String(b.key())).to.equal('QmeoBGh5g5kHgK3xppJ1YPwB9xgH2GoqhMSuQVpzDdvtJG')
+    expect(multihash.toB58String(b.key('sha1'))).to.equal('5dsvLgRV9RVj9eSgtxMrXQjbpfFeHY')
     expect(b.data).to.exist
-    expect(b.extension).to.be.eql('data')
   })
 
   it('fail to create an empty block', () => {
@@ -33,28 +34,9 @@ describe('block', () => {
     // it from the original implementation
     // It doesn't stricly verify the immutability of the Block object
     const block = new Block("Can't change this!")
-    let key = block.key
+    let key = block.key()
     key = new Buffer('new key')
 
-    expect(key.equals(block.key)).to.equal(false)
-  })
-
-  it('has the right extension to type mapping', () => {
-    const b1 = new Block('hello', 'protobuf')
-    const b2 = new Block('hello')
-    const b3 = new Block('hello', 'ipld')
-    const b4 = new Block('hello', 'woot')
-
-    expect(b1.type).to.be.eql('protobuf')
-    expect(b1.extension).to.be.eql('data')
-
-    expect(b2.type).to.be.eql('protobuf')
-    expect(b2.extension).to.be.eql('data')
-
-    expect(b3.type).to.be.eql('ipld')
-    expect(b3.extension).to.be.eql('ipld')
-
-    expect(b4.type).to.be.eql('woot')
-    expect(b4.extension).to.be.eql('woot')
+    expect(key.equals(block.key())).to.equal(false)
   })
 })