diff --git a/contracts/mocks/Pack.sol b/contracts/mocks/Pack.sol
index 7c8a4f7..1c3bce0 100644
--- a/contracts/mocks/Pack.sol
+++ b/contracts/mocks/Pack.sol
@@ -24,11 +24,11 @@ contract Pack {
     uint256 gasBefore = gasleft();
     bytes memory data = new bytes(BYTES_SIZE);
     for (uint256 i = 0; i < CHUNK_SIZE; i++) {
-      (bytes32 hash, address instance, uint32 block) = (hashes[i], instances[i], blocks[i]);
+      (bytes32 _hash, address _instance, uint32 _block) = (hashes[i], instances[i], blocks[i]);
       assembly {
-        mstore(add(add(data, mul(ITEM_SIZE, i)), 0x38), block)
-        mstore(add(add(data, mul(ITEM_SIZE, i)), 0x34), instance)
-        mstore(add(add(data, mul(ITEM_SIZE, i)), 0x20), hash)
+        mstore(add(add(data, mul(ITEM_SIZE, i)), 0x38), _block)
+        mstore(add(add(data, mul(ITEM_SIZE, i)), 0x34), _instance)
+        mstore(add(add(data, mul(ITEM_SIZE, i)), 0x20), _hash)
       }
     }
     uint256 gasHash = gasleft();
@@ -52,23 +52,23 @@ contract Pack {
     public
     view
     returns (
-      uint256 gas1,
-      uint256 gas2,
-      bytes32 hash
+      uint256,
+      uint256,
+      bytes32
     )
   {
     uint256 gasBefore = gasleft();
     bytes memory data = new bytes(BYTES_SIZE);
     for (uint256 i = 0; i < CHUNK_SIZE; i++) {
-      (bytes32 hash, address instance, uint32 block) = (hashes[i], instances[i], blocks[i]);
+      (bytes32 _hash, address _instance, uint32 _block) = (hashes[i], instances[i], blocks[i]);
       assembly {
-        mstore(add(add(data, mul(ITEM_SIZE, i)), 0x38), block)
-        mstore(add(add(data, mul(ITEM_SIZE, i)), 0x34), instance)
-        mstore(add(add(data, mul(ITEM_SIZE, i)), 0x20), hash)
+        mstore(add(add(data, mul(ITEM_SIZE, i)), 0x38), _block)
+        mstore(add(add(data, mul(ITEM_SIZE, i)), 0x34), _instance)
+        mstore(add(add(data, mul(ITEM_SIZE, i)), 0x20), _hash)
       }
     }
     uint256 gasHash = gasleft();
-    bytes32 hash = sha256(data);
-    return (gasleft() - gasHash, gasHash - gasBefore, hash);
+    bytes32 hash1 = sha256(data);
+    return (gasleft() - gasHash, gasHash - gasBefore, hash1);
   }
 }
diff --git a/package.json b/package.json
index e6bbc4c..3f4c2e5 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "tornado-trees",
-  "version": "0.0.7",
+  "version": "0.0.8",
   "main": "src/index.js",
   "repository": "https://github.com/tornadocash/tornado-trees.git",
   "author": "Tornadocash team <hello@tornado.cash>",
@@ -46,6 +46,7 @@
     "circomlib": "git+https://github.com/tornadocash/circomlib.git#d20d53411d1bef61f38c99a8b36d5d0cc4836aa1",
     "dotenv": "^8.2.0",
     "ffiasm": "^0.1.1",
+    "ffjavascript": "^0.2.35",
     "fixed-merkle-tree": "^0.5.0",
     "jssha": "^3.2.0",
     "snarkjs": "^0.3.57",
diff --git a/src/index.js b/src/index.js
index 8fc6c9b..bc30643 100644
--- a/src/index.js
+++ b/src/index.js
@@ -1,5 +1,7 @@
 const ethers = require('ethers')
 const BigNumber = ethers.BigNumber
+const { wtns } = require('snarkjs')
+const { utils } = require('ffjavascript')
 
 const { bitsToNumber, toBuffer, toFixedHex, poseidonHash } = require('./utils')
 
@@ -32,16 +34,17 @@ function hashInputs(input) {
 function prove(input, keyBasePath) {
   return tmp.dir().then(async (dir) => {
     dir = dir.path
-    fs.writeFileSync(`${dir}/input.json`, JSON.stringify(input, null, 2))
     let out
 
     try {
       if (fs.existsSync(`${keyBasePath}`)) {
         // native witness calc
+        fs.writeFileSync(`${dir}/input.json`, JSON.stringify(input, null, 2))
         out = await exec(`${keyBasePath} ${dir}/input.json ${dir}/witness.json`)
       } else {
-        out = await exec(`npx snarkjs wd ${keyBasePath}.wasm ${dir}/input.json ${dir}/witness.wtns`)
-        out = await exec(`npx snarkjs wej ${dir}/witness.wtns ${dir}/witness.json`)
+        await wtns.calculate(utils.unstringifyBigInts(input), `${keyBasePath}.wasm`, `${dir}/witness.wtns`)
+        const witness = utils.stringifyBigInts(await wtns.exportJson(`${dir}/witness.wtns`))
+        fs.writeFileSync(`${dir}/witness.json`, JSON.stringify(witness, null, 2))
       }
       out = await exec(
         `zkutil prove -c ${keyBasePath}.r1cs -p ${keyBasePath}.params -w ${dir}/witness.json -r ${dir}/proof.json -o ${dir}/public.json`,
diff --git a/yarn.lock b/yarn.lock
index 52f4ae4..e1d0373 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -3890,6 +3890,15 @@ ffjavascript@0.2.34, ffjavascript@^0.2.30:
     wasmcurves "0.0.14"
     worker-threads "^1.0.0"
 
+ffjavascript@^0.2.35:
+  version "0.2.35"
+  resolved "https://registry.yarnpkg.com/ffjavascript/-/ffjavascript-0.2.35.tgz#9166d95173b1c0a743b455bb03a72b581922a42e"
+  integrity sha512-xnC51tWbi0ah4SH+02jEfJyO+P+NiZWnxQrLDLtBYY1Dv3QM5ydxzd+gxnLEfWdT8i1bMM5pIh5P25l6fNCaVQ==
+  dependencies:
+    big-integer "^1.6.48"
+    wasmcurves "0.0.14"
+    web-worker "^1.0.0"
+
 ffwasm@0.0.7:
   version "0.0.7"
   resolved "https://registry.yarnpkg.com/ffwasm/-/ffwasm-0.0.7.tgz#23bb9a3537ecc87c0f24fcfb3a9ddd0e86855fff"
@@ -8352,6 +8361,11 @@ wasmcurves@0.0.5:
     big-integer "^1.6.42"
     blakejs "^1.1.0"
 
+web-worker@^1.0.0:
+  version "1.0.0"
+  resolved "https://registry.yarnpkg.com/web-worker/-/web-worker-1.0.0.tgz#c7ced4e1eb6227636ada35056a9e5a477414e4d0"
+  integrity sha512-BzuMqeKVkKKwHV6tJuwePFcxYMxvC97D448mXTgh/CxXAB4sRtoV26gRPN+JDxsXRR7QZyioMV9O6NzQaASf7Q==
+
 web3-bzz@1.2.11:
   version "1.2.11"
   resolved "https://registry.yarnpkg.com/web3-bzz/-/web3-bzz-1.2.11.tgz#41bc19a77444bd5365744596d778b811880f707f"