diff --git a/assembly/cache.ts b/assembly/cache.ts
new file mode 100644
index 0000000..59b134f
--- /dev/null
+++ b/assembly/cache.ts
@@ -0,0 +1,2 @@
+export declare function load(ptr: u32, offset: u32, len: u32): void;
+export declare function save(ptr: u32, offset: u32, len: u32): void;
diff --git a/assembly/hello-world/index.ts b/assembly/hello-world/index.ts
index 6823245..98258cb 100644
--- a/assembly/hello-world/index.ts
+++ b/assembly/hello-world/index.ts
@@ -1,8 +1,9 @@
 import * as env from '../env'
 import * as bignum from '../bignum'
+import * as cache from '../cache'
 
 /*
- * Increments preStateRoot by one
+ * Increments preStateRoot by the cached value of previous block data
  */
 export function main(): void {
   var preStateRootPtr: u32 = __heap_base
@@ -11,9 +12,13 @@ export function main(): void {
   var postStateRootPtr: u32 = __heap_base + 32
 
   var numPtr: u32 = __heap_base + 64
-  store<u8>(numPtr, 1, 31)
+  cache.load(numPtr, 0, 32)
 
   bignum.add256(preStateRootPtr, numPtr, postStateRootPtr)
 
+  var blockDataPtr: u32 = __heap_base + 96
+  env.eth2_blockDataCopy(blockDataPtr, 0, 32)
+  cache.save(blockDataPtr, 0, 32)
+
   env.eth2_savePostStateRoot(postStateRootPtr)
 }
diff --git a/src/browser.js b/src/browser.js
index 674f117..b83f99e 100644
--- a/src/browser.js
+++ b/src/browser.js
@@ -1,5 +1,5 @@
 const { safeLoad } = require('js-yaml')
-const { TestCase, parseYaml, getImports, setMemory, getRes } = require('../dist/lib')
+const { TestCase, parseYaml, getImports, setMemory, getRes, CACHE_SIZE } = require('../dist/lib')
 
 async function main() {
   let yamlPath = 'test.yaml'
@@ -10,12 +10,17 @@ async function main() {
     const wasmResponse = await fetch(testCase.script)
     const wasmBuffer = await wasmResponse.arrayBuffer()
     let preStateRoot = testCase.preStateRoot
+    let readableCache = Buffer.alloc(CACHE_SIZE)
+    let writableCache = Buffer.alloc(CACHE_SIZE)
     for (const block of testCase.blocks) {
-      const compiled = await WebAssembly.instantiate(wasmBuffer, getImports({ preStateRoot, blockData: block }))
+      const compiled = await WebAssembly.instantiate(wasmBuffer, getImports({ preStateRoot, blockData: block, readableCache, writableCache }))
       const instance = compiled.instance
       setMemory(instance.exports.memory)
       instance.exports.main()
       preStateRoot = getRes()
+
+      readableCache = writableCache
+      writableCache = Buffer.alloc(CACHE_SIZE)
     }
     if (!testCase.postStateRoot.equals(getRes())) {
       console.error('Assertion failed, post state root doesn\'t match')
diff --git a/src/cli.ts b/src/cli.ts
index c769038..2fe44ef 100644
--- a/src/cli.ts
+++ b/src/cli.ts
@@ -1,7 +1,7 @@
 import * as assert from 'assert'
 import * as fs from 'fs'
 import { safeLoad } from 'js-yaml'
-import { TestCase, parseYaml, getImports, setMemory, getRes } from './lib'
+import { TestCase, parseYaml, getImports, setMemory, getRes, CACHE_SIZE } from './lib'
 
 function main() {
   let yamlPath
@@ -19,14 +19,21 @@ function main() {
     const wasmFile = fs.readFileSync(testCase.script)
     const wasmModule = new WebAssembly.Module(wasmFile)
     let preStateRoot = testCase.preStateRoot
+    let readableCache = Buffer.alloc(CACHE_SIZE)
+    let writableCache = Buffer.alloc(CACHE_SIZE)
     for (const block of testCase.blocks) {
-      const instance = new WebAssembly.Instance(wasmModule, getImports({ preStateRoot, blockData: block }))
+      const instance = new WebAssembly.Instance(wasmModule, getImports({ preStateRoot, blockData: block, readableCache, writableCache }))
       setMemory(instance.exports.memory)
+
       let t = process.hrtime()
       instance.exports.main()
       t = process.hrtime(t)
       console.log('benchmark took %d seconds and %d nanoseconds (%d ms)', t[0], t[1], t[1] / 1000000)
+
       preStateRoot = getRes()
+
+      readableCache = writableCache
+      writableCache = Buffer.alloc(CACHE_SIZE)
     }
     assert(testCase.postStateRoot.equals(getRes()), `expected ${testCase.postStateRoot.toString('hex')}, received ${getRes().toString('hex')}`)
   }
diff --git a/src/lib.ts b/src/lib.ts
index 9b0b085..e720c68 100644
--- a/src/lib.ts
+++ b/src/lib.ts
@@ -4,6 +4,9 @@ import { safeLoad } from 'js-yaml'
 import BN = require('bn.js')
 import { TWO_POW256 } from 'ethereumjs-util'
 
+// Cache size in bytes
+export const CACHE_SIZE = 256 * 1024
+
 let mem: WebAssembly.Memory
 let res: Buffer
 
@@ -37,6 +40,8 @@ export interface TestCase {
 export interface EnvData {
   preStateRoot: Buffer
   blockData: Buffer
+  readableCache: Buffer
+  writableCache: Buffer
 }
 
 export const getImports = (env: EnvData) => {
@@ -58,6 +63,16 @@ export const getImports = (env: EnvData) => {
       debug_endTimer: () => console.log('end timer'),
       abort: () => { throw ('Wasm aborted') }
     },
+    cache: {
+      load: (ptr: number, offset: number, len: number) => {
+        const c = env.readableCache.slice(offset, offset + len)
+        memset(mem, ptr, c)
+      },
+      save: (ptr: number, offset: number, len: number) => {
+        const c = memget(mem, ptr, len)
+        env.writableCache.write(c.toString('hex'), offset, len, 'hex')
+      }
+    },
     bignum: {
       add256: (aOffset: number, bOffset: number, cOffset: number) => {
         const a = new BN(memget(mem, aOffset, 32))
diff --git a/test.yaml b/test.yaml
index a491ad2..be04c54 100644
--- a/test.yaml
+++ b/test.yaml
@@ -6,9 +6,11 @@ shard_pre_state:
     - "0000000000000000000000000000000000000000000000000000000000000001"
 shard_blocks:
   - env: 0
-    data: ""
+    data: "0000000000000000000000000000000000000000000000000000000000000005"
   - env: 0
-    data: ""
+    data: "0000000000000000000000000000000000000000000000000000000000000007"
+  - env: 0
+    data: "000000000000000000000000000000000000000000000000000000000000000b"
 shard_post_state:
   exec_env_states:
-    - "0000000000000000000000000000000000000000000000000000000000000003"
+    - "000000000000000000000000000000000000000000000000000000000000000d"