diff --git a/cli.js b/cli.js
index a7ee5bc..2b6a50f 100755
--- a/cli.js
+++ b/cli.js
@@ -133,7 +133,7 @@ const commands = [
         cmd: "powersoftau import <powersoftau_old.ptau> <response> <<powersoftau_new.ptau>",
         description: "import a response to a ptau file",
         alias: ["pti"],
-        options: "-verbose|v -nopoints -nocheck -description|d -name|n",
+        options: "-verbose|v -nopoints -nocheck -name|n",
         action: powersOfTawImport
     },
     {
@@ -204,7 +204,7 @@ const commands = [
         cmd: "zkey contribute <circuit_old.zkey> <circuit_new.zkey>",
         description: "creates a zkey file with a new contribution",
         alias: ["zkc"],
-        options: "-verbose|v",
+        options: "-verbose|v  -entropy|e -name|n",
         action: zkeyContribute
     },
     {
@@ -772,7 +772,7 @@ async function zkeyNew(params, options) {
         zkeyName = params[2];
     }
 
-    return phase2.new(r1csName, ptauName, zkeyName, options.verbose);
+    return zkey.new(r1csName, ptauName, zkeyName, options.verbose);
 }
 
 // zkey export bellman [circuit.zkey] [circuit.mpcparams]
@@ -792,7 +792,7 @@ async function zkeyExportBellman(params, options) {
         mpcparamsName = params[1];
     }
 
-    return phase2.exportMPCParams(zkeyName, mpcparamsName, options.verbose);
+    return zkey.exportMPCParams(zkeyName, mpcparamsName, options.verbose);
 
 }
 
@@ -846,8 +846,7 @@ async function zkeyVerify(params, options) {
 }
 
 
-// phase2 contribute <circuit_old.zkey> <circuit_new.zkey>
-
+// zkey contribute <circuit_old.zkey> <circuit_new.zkey>
 async function zkeyContribute(params, options) {
     let zkeyOldName;
     let zkeyNewName;
@@ -856,5 +855,5 @@ async function zkeyContribute(params, options) {
     zkeyNewName = params[1];
 
 
-    return phase2.contribute(zkeyOldName, zkeyNewName, options.verbose);
+    return zkey.contribute(zkeyOldName, zkeyNewName, options.name, options.entropy, options.verbose);
 }
diff --git a/src/keypair.js b/src/keypair.js
index 659c33a..d54553b 100644
--- a/src/keypair.js
+++ b/src/keypair.js
@@ -7,7 +7,7 @@ const blake2b = require("blake2b");
 const ChaCha = require("ffjavascript").ChaCha;
 
 function hashToG2(hash) {
-    const hashV = new DataView(hash.buffer);
+    const hashV = new DataView(hash.buffer, hash.byteOffset, hash.byteLength);
     const seed = [];
     for (let i=0; i<8; i++) {
         seed[i] = hashV.getUint32(i*4);
@@ -57,6 +57,17 @@ function createPTauKey(curve, challangeHash, rng) {
     return key;
 }
 
+function createDeltaKey(curve, transcript, rng) {
+    const delta = {};
+    delta.prvKey = curve.Fr.fromRng(rng);
+    delta.g1_s = curve.G1.affine(curve.G1.fromRng(rng));
+    delta.g1_sx = curve.G1.affine(curve.G1.mulScalar(delta.g1_s, delta.prvKey));
+    delta.g2_sp = hashToG2(transcript);
+    delta.g2_spx = curve.G2.affine(curve.G2.mulScalar(delta.g2_sp, delta.prvKey));
+    return delta;
+}
+
 module.exports.createPTauKey = createPTauKey;
 module.exports.getG2sp = getG2sp;
 module.exports.hashToG2 = hashToG2;
+module.exports.createDeltaKey =createDeltaKey;
diff --git a/src/misc.js b/src/misc.js
index cdeccab..cb26c65 100644
--- a/src/misc.js
+++ b/src/misc.js
@@ -1,4 +1,7 @@
 const Blake2b = require("blake2b-wasm");
+const readline = require("readline");
+const ChaCha = require("ffjavascript").ChaCha;
+const crypto = require("crypto");
 
 const _revTable = [];
 for (let i=0; i<256; i++) {
@@ -74,9 +77,42 @@ async function sameRatio(curve, g1s, g1sx, g2s, g2sx) {
     return res;
 }
 
+
+
+const rl = readline.createInterface({
+    input: process.stdin,
+    output: process.stdout
+});
+
+function askEntropy() {
+    return new Promise((resolve) => {
+        rl.question("Enter a random text. (Entropy): ", (input) => resolve(input) );
+    });
+}
+
+async function getRandomRng(entropy) {
+    // Generate a random key
+    while (!entropy) {
+        entropy = await askEntropy();
+    }
+    const hasher = Blake2b(64);
+    hasher.update(crypto.randomBytes(64));
+    const enc = new TextEncoder(); // always utf-8
+    hasher.update(enc.encode(entropy));
+    const hash = Buffer.from(hasher.digest());
+
+    const seed = [];
+    for (let i=0;i<8;i++) {
+        seed[i] = hash.readUInt32BE(i*4);
+    }
+    const rng = new ChaCha(seed);
+    return rng;
+}
+
 module.exports.bitReverse = bitReverse;
 module.exports.log2 = log2;
 module.exports.formatHash = formatHash;
 module.exports.hashIsEqual = hashIsEqual;
 module.exports.cloneHasher = cloneHasher;
 module.exports.sameRatio = sameRatio;
+module.exports.getRandomRng = getRandomRng;
diff --git a/src/mpc_applykey.js b/src/mpc_applykey.js
index 859f55d..3fa5065 100644
--- a/src/mpc_applykey.js
+++ b/src/mpc_applykey.js
@@ -1,5 +1,6 @@
 
 const buildTaskManager = require("./taskmanager");
+const binFileUtils = require("./binfileutils");
 
 /*
     This function creates a new section in the fdTo file with id idSection.
@@ -8,116 +9,36 @@ const buildTaskManager = require("./taskmanager");
     It also updates the newChallangeHasher with the new points
 */
 
-async function applyKey(params) {
-    const {
-        fdFrom,
-        sections,
-        curve,
-        fdTo,
-        sectionId,
-        NPoints,
-        G:Gs,
-        first,
-        inc,
-        newChallangeHasher,
-        responseHasher,
-        returnPoints,
-        sectionName,
-        verbose
-    } = params;
-    const G = curve[Gs];
-    const MAX_CHUNK_SIZE = 1024;
-
-    let res = [];
+async function applyKeyToSection(fdOld, sections, fdNew, idSection, curve, groupName, first, inc, sectionName, verbose) {
+    const MAX_CHUNK_SIZE = 1 << 16;
+    const G = curve[groupName];
     const sG = G.F.n8*2;
-    const buffUv = new Uint8Array(sG);
-    const scG = G.F.n8;
-    const buffCv = new Uint8Array(scG);
+    const nPoints = sections[idSection][0].size / sG;
 
-    const taskManager = await buildTaskManager(contributeThread, {
-        ffjavascript: "ffjavascript"
-    },{
-        curve: curve.name
-    });
+    await binFileUtils.startReadUniqueSection(fdOld, sections,idSection );
+    await binFileUtils.startWriteSection(fdNew, idSection);
 
-    fdFrom.pos = sections[sectionId][0].p;
-    await fdTo.writeULE32(sectionId); // tauG1
-    const pSection = fdTo.pos;
-    await fdTo.writeULE64(0); // Temporally set to 0 length
     let t = first;
-    let writePointer = fdTo.pos;
-    let beginWritePointer = fdTo.pos;
-    for (let i=0; i< NPoints; i+=MAX_CHUNK_SIZE) {
-        if ((verbose)&&i) console.log(`${sectionName}: ` + i);
-        const n = Math.min(NPoints - i, MAX_CHUNK_SIZE);
-        const buff = await fdFrom.read(n*sG);
-        await taskManager.addTask({
-            cmd: "MUL",
-            G: Gs,
-            first: t,
-            inc: inc.toString(),
-            buff: buff.slice(),
-            n: n,
-            writePos: writePointer
-        }, async function(r) {
-            return await fdTo.write(r.buff, r.writePos);
-        });
+    for (let i=0; i<nPoints; i += MAX_CHUNK_SIZE) {
+        if (verbose) console.log(`Applying key: ${sectionName}: ${i}/${nPoints}`);
+        const n= Math.min(nPoints - i, MAX_CHUNK_SIZE);
+        let buff;
+        buff = await fdOld.read(n*sG);
+        buff = await G.batchApplyKey(buff, t, inc);
+        await fdNew.write(buff);
         t = curve.Fr.mul(t, curve.Fr.pow(inc, n));
-        writePointer += n*sG;
     }
 
-    await taskManager.finish();
+    await binFileUtils.endWriteSection(fdNew);
+    await binFileUtils.endReadSection(fdOld);
 
-    const sSize  = fdTo.pos - pSection -8;
-    const lastPos = fdTo.pos;
-    await fdTo.writeULE64(sSize, pSection);
-    fdTo.pos = lastPos;
 
-    fdTo.pos = beginWritePointer;
-    for (let i=0; i<NPoints; i++) {
-        const buff = await fdTo.read(sG);
-        const P = G.fromRprLEM(buff, 0);
-        G.toRprBE(buffUv, 0, P);
-        newChallangeHasher.update(buffUv);
-        G.toRprCompressed(buffCv, 0, P);
-        responseHasher.update(buffCv);
-        const idx = returnPoints.indexOf(i);
-        if (idx>=0) res[idx] =  P;
-    }
+}
+
+async function applyKeyToBinFile(fdOld, fdNew, curve, groupName, nPoints, first, inc, sectionName, verbose) {
 
-    return res;
 }
 
 
-function contributeThread(ctx, task) {
-    if (task.cmd == "INIT") {
-        ctx.assert = ctx.modules.assert;
-        if (task.curve == "bn128") {
-            ctx.curve = ctx.modules.ffjavascript.bn128;
-        } else {
-            ctx.assert(false, "curve not defined");
-        }
-        return {};
-    } else if (task.cmd == "MUL") {
-        const G = ctx.curve[task.G];
-        const sG = G.F.n64*8*2;
-        const buffDest = new Uint8Array(sG*task.n);
-        let t = ctx.curve.Fr.e(task.first);
-        let inc = ctx.curve.Fr.e(task.inc);
-        for (let i=0; i<task.n; i++) {
-            const P = G.fromRprLEM(task.buff, i*sG);
-            const R = G.mulScalar(P, t);
-            G.toRprLEM(buffDest, i*sG, R);   // Main thread will convert it to Montgomery
-            t = ctx.curve.Fr.mul(t, inc);
-        }
-        return {
-            buff: buffDest,
-            writePos: task.writePos
-        };
-    } else {
-        ctx.assert(false, "Op not implemented");
-    }
-}
-
-
-module.exports = applyKey;
+module.exports.applyKeyToBinFile = applyKeyToBinFile;
+module.exports.applyKeyToSection = applyKeyToSection;
diff --git a/src/zkey_contribute.js b/src/zkey_contribute.js
index fb11d57..a74b1b2 100644
--- a/src/zkey_contribute.js
+++ b/src/zkey_contribute.js
@@ -1,4 +1,87 @@
 
-module.exports  = async function phase2contribute(zkeyNameOld, zkeyNameNew, verbose) {
+const binFileUtils = require("./binfileutils");
+const zkeyUtils = require("./zkey_utils");
+const getCurve = require("./curves").getCurveFromQ;
+const misc = require("./misc");
+const Blake2b = require("blake2b-wasm");
+const utils = require("./zkey_utils");
+const hashToG2 = require("./keypair").hashToG2;
+const {applyKeyToSection} = require("./mpc_applykey");
 
+module.exports  = async function phase2contribute(zkeyNameOld, zkeyNameNew, name, entropy, verbose) {
+    await Blake2b.ready();
+
+    const {fd: fdOld, sections: sections} = await binFileUtils.readBinFile(zkeyNameOld, "zkey", 2);
+    const zkey = await zkeyUtils.readHeader(fdOld, sections, "groth16");
+
+    const curve = getCurve(zkey.q);
+    await curve.loadEngine();
+
+    const mpcParams = await zkeyUtils.readMPCParams(fdOld, curve, sections);
+
+    const fdNew = await binFileUtils.createBinFile(zkeyNameNew, "zkey", 1, 10);
+
+    const curContribution = {};
+
+    const rng = await misc.getRandomRng(entropy);
+
+    const transcriptHasher = Blake2b(64);
+    for (let i=0; i<mpcParams.contributions.length; i++) {
+        utils.hashPubKey(transcriptHasher, curve, mpcParams.contributions[i]);
+    }
+
+    curContribution.delta = {};
+    curContribution.delta.prvKey = curve.Fr.fromRng(rng);
+    curContribution.delta.g1_s = curve.G1.affine(curve.G1.fromRng(rng));
+    curContribution.delta.g1_sx = curve.G1.affine(curve.G1.mulScalar(curContribution.delta.g1_s, curContribution.delta.prvKey));
+    utils.hashG1(transcriptHasher, curve, curContribution.delta.g1_s);
+    utils.hashG1(transcriptHasher, curve, curContribution.delta.g1_sx);
+    curContribution.transcript = transcriptHasher.digest();
+    curContribution.delta.g2_sp = hashToG2(curContribution.transcript);
+    curContribution.delta.g2_spx = curve.G2.affine(curve.G2.mulScalar(curContribution.delta.g2_sp, curContribution.delta.prvKey));
+
+    zkey.vk_delta_1 = curve.G1.mulScalar(zkey.vk_delta_1, curContribution.delta.prvKey);
+    zkey.vk_delta_2 = curve.G2.mulScalar(zkey.vk_delta_2, curContribution.delta.prvKey);
+
+    curContribution.deltaAfter = zkey.vk_delta_1;
+    mpcParams.contributions.push(curContribution);
+
+    curContribution.type = 0;
+    if (name) curContribution.name = name;
+
+    await zkeyUtils.writeHeader(fdNew, zkey);
+
+    // IC
+    await binFileUtils.copySection(fdOld, sections, fdNew, 3);
+
+    // Coeffs (Keep original)
+    await binFileUtils.copySection(fdOld, sections, fdNew, 4);
+
+    // A Section
+    await binFileUtils.copySection(fdOld, sections, fdNew, 5);
+
+    // B1 Section
+    await binFileUtils.copySection(fdOld, sections, fdNew, 6);
+
+    // B2 Section
+    await binFileUtils.copySection(fdOld, sections, fdNew, 7);
+
+    const invDelta = curve.Fr.inv(curContribution.delta.prvKey);
+    await applyKeyToSection(fdOld, sections, fdNew, 8, curve, "G1", invDelta, curve.Fr.e(1), "L Section", verbose);
+    await applyKeyToSection(fdOld, sections, fdNew, 9, curve, "G1", invDelta, curve.Fr.e(1), "H Section", verbose);
+
+    await zkeyUtils.writeMPCParams(fdNew, curve, mpcParams);
+
+    await fdOld.close();
+    await fdNew.close();
+
+    const contributionHasher = Blake2b(64);
+    utils.hashPubKey(contributionHasher, curve, curContribution);
+
+    const contribuionHash = contributionHasher.digest();
+
+    console.log("Contribution Hash: ");
+    console.log(misc.formatHash(contribuionHash));
+
+    return true;
 };
diff --git a/src/zkey_new.js b/src/zkey_new.js
index 746e708..26260fe 100644
--- a/src/zkey_new.js
+++ b/src/zkey_new.js
@@ -395,7 +395,7 @@ module.exports  = async function phase2new(r1csName, ptauName, zkeyName, verbose
 
 
     async function hashHPoints() {
-        const CHUNK_SIZE = 1<<20;
+        const CHUNK_SIZE = 1<<16;
 
         hashU32(domainSize-1);
 
diff --git a/src/zkey_utils.js b/src/zkey_utils.js
index a00f3c2..a2ba707 100644
--- a/src/zkey_utils.js
+++ b/src/zkey_utils.js
@@ -346,6 +346,33 @@ async function readContribution(fd, curve) {
     c.delta.g1_sx = await readG1(fd, curve);
     c.delta.g2_spx = await readG2(fd, curve);
     c.transcript = await fd.read(64);
+    c.type = await fd.readULE32();
+
+    const paramLength = await fd.readULE32();
+    const curPos = fd.pos;
+    let lastType =0;
+    while (fd.pos-curPos < paramLength) {
+        const buffType = await fd.read(1);
+        if (buffType[0]<= lastType) throw new Error("Parameters in the contribution must be sorted");
+        lastType = buffType[0];
+        if (buffType[0]==1) {     // Name
+            const buffLen = await fd.read(1);
+            const buffStr = await fd.read(buffLen[0]);
+            c.name = new TextDecoder().decode(buffStr);
+        } else if (buffType[0]==2) {
+            const buffExp = await fd.read(1);
+            c.numIterationsExp = buffExp[0];
+        } else if (buffType[0]==3) {
+            const buffLen = await fd.read(1);
+            c.beaconHash = await fd.read(buffLen[0]);
+        } else {
+            throw new Error("Parameter not recognized");
+        }
+    }
+    if (fd.pos != curPos + paramLength) {
+        throw new Error("Parametes do not match");
+    }
+
     return c;
 }
 
@@ -370,6 +397,31 @@ async function writeContribution(fd, curve, c) {
     await writeG1(fd, curve, c.delta.g1_sx);
     await writeG2(fd, curve, c.delta.g2_spx);
     await fd.write(c.transcript);
+    await fd.writeULE32(c.type || 0);
+
+    const params = [];
+    if (c.name) {
+        params.push(1);      // Param Name
+        const nameData = new TextEncoder("utf-8").encode(c.name.substring(0,64));
+        params.push(nameData.byteLength);
+        for (let i=0; i<nameData.byteLength; i++) params.push(nameData[i]);
+    }
+    if (c.type == 1) {
+        params.push(2);      // Param numIterationsExp
+        params.push(c.numIterationsExp);
+
+        params.push(3);      // Beacon Hash
+        params.push(c.beaconHash.byteLength);
+        for (let i=0; i<c.beaconHash.byteLength; i++) params.push(c.beaconHash[i]);
+    }
+    if (params.length>0) {
+        const paramsBuff = new Uint8Array(params);
+        await fd.writeULE32(paramsBuff.byteLength);
+        await fd.write(paramsBuff);
+    } else {
+        await fd.writeULE32(0);
+    }
+
 }
 
 async function writeMPCParams(fd, curve, mpcParams) {
@@ -382,9 +434,33 @@ async function writeMPCParams(fd, curve, mpcParams) {
     await binFileUtils.endWriteSection(fd);
 }
 
+function hashG1(hasher, curve, p) {
+    const buff = new Uint8Array(curve.G1.F.n8*2);
+    curve.G1.toRprUncompressed(buff, 0, p);
+    hasher.update(buff);
+}
+
+function hashG2(hasher,curve, p) {
+    const buff = new Uint8Array(curve.G2.F.n8*2);
+    curve.G2.toRprUncompressed(buff, 0, p);
+    hasher.update(buff);
+}
+
+function hashPubKey(hasher, curve, c) {
+    hashG1(hasher, curve, c.deltaAfter);
+    hashG1(hasher, curve, c.delta.g1_s);
+    hashG1(hasher, curve, c.delta.g1_sx);
+    hashG2(hasher, curve, c.delta.g2_spx);
+    hasher.update(c.transcript);
+}
+
+
 module.exports.readHeader = readHeader;
 module.exports.writeHeader = writeHeader;
 module.exports.read = readZKey;
 module.exports.write = writeZKey;
 module.exports.readMPCParams = readMPCParams;
 module.exports.writeMPCParams = writeMPCParams;
+module.exports.hashG1 = hashG1;
+module.exports.hashG2 = hashG2;
+module.exports.hashPubKey = hashPubKey;
diff --git a/src/zkey_verify.js b/src/zkey_verify.js
index 193b2aa..038d527 100644
--- a/src/zkey_verify.js
+++ b/src/zkey_verify.js
@@ -9,6 +9,7 @@ const sameRatio = misc.sameRatio;
 const crypto = require("crypto");
 const ChaCha = require("ffjavascript").ChaCha;
 const newZKey = require("./zkey_new");
+const {hashG1, hashPubKey} = require("./zkey_utils");
 
 
 module.exports  = async function phase2verify(r1csFileName, pTauFileName, zkeyFileName, verbose) {
@@ -34,8 +35,8 @@ module.exports  = async function phase2verify(r1csFileName, pTauFileName, zkeyFi
         const c = mpcParams.contributions[i];
         const ourHasher = misc.cloneHasher(accumulatedHasher);
 
-        hashG1(ourHasher, c.delta.g1_s);
-        hashG1(ourHasher, c.delta.g1_sx);
+        hashG1(ourHasher, curve, c.delta.g1_s);
+        hashG1(ourHasher, curve, c.delta.g1_sx);
 
         if (!misc.hashIsEqual(ourHasher.digest(), c.transcript)) {
             console.log(`INVALID(${i}): Inconsistent transcript `);
@@ -56,10 +57,10 @@ module.exports  = async function phase2verify(r1csFileName, pTauFileName, zkeyFi
             return false;
         }
 
-        hashPubKey(accumulatedHasher, c);
+        hashPubKey(accumulatedHasher, curve, c);
 
         const contributionHasher = Blake2b(64);
-        hashPubKey(contributionHasher, c);
+        hashPubKey(contributionHasher, curve, c);
         responses.push(contributionHasher.digest());
 
         curDelta = c.deltaAfter;
@@ -181,27 +182,6 @@ module.exports  = async function phase2verify(r1csFileName, pTauFileName, zkeyFi
 
     return true;
 
-    function hashG1(hasher, p) {
-        const buff = new Uint8Array(sG1);
-        curve.G1.toRprUncompressed(buff, 0, p);
-        hasher.update(buff);
-    }
-
-    function hashG2(hasher, p) {
-        const buff = new Uint8Array(sG2);
-        curve.G2.toRprUncompressed(buff, 0, p);
-        hasher.update(buff);
-    }
-
-    function hashPubKey(hasher, c) {
-        hashG1(hasher, c.deltaAfter);
-        hashG1(hasher, c.delta.g1_s);
-        hashG1(hasher, c.delta.g1_sx);
-        hashG2(hasher, c.delta.g2_spx);
-        hasher.update(c.transcript);
-    }
-
-
 
     async function sectionHasSameRatio(groupName, fd1, sections1, fd2, sections2, idSection, g2sp, g2spx, sectionName) {
         const MAX_CHUNK_SIZE = 1<<20;