diff --git a/packages/protocols/README.md b/packages/protocols/README.md
index bfa3110..4a0a440 100644
--- a/packages/protocols/README.md
+++ b/packages/protocols/README.md
@@ -66,7 +66,7 @@ import { generateMerkleProof } from "@zk-kit/protocols"
 
 const depth = 20
 const zeroValue = BigInt(0)
-const arity = 5
+const arity = 2
 const identity = new ZkIdentity()
 const identityCommitment = identity.genIdentityCommitment()
 const identityCommitments = [BigInt(1), identityCommitment, BigInt(2)]
diff --git a/packages/protocols/src/semaphore.ts b/packages/protocols/src/semaphore.ts
index d49d9f3..03e6bd7 100644
--- a/packages/protocols/src/semaphore.ts
+++ b/packages/protocols/src/semaphore.ts
@@ -24,12 +24,12 @@ export default class Semaphore extends ZkProtocol {
     shouldHash = true
   ): SemaphoreWitness {
     return {
-      identity_nullifier: identityNullifier,
-      identity_trapdoor: identityTrapdoor,
-      identity_path_index: merkleProof.pathIndices,
-      path_elements: merkleProof.siblings,
-      external_nullifier: externalNullifier,
-      signal_hash: shouldHash ? genSignalHash(signal) : signal
+      identityNullifier,
+      identityTrapdoor,
+      treePathIndices: merkleProof.pathIndices,
+      treeSiblings: merkleProof.siblings,
+      externalNullifier,
+      signalHash: shouldHash ? genSignalHash(signal) : signal
     }
   }
 
diff --git a/packages/protocols/src/types/index.ts b/packages/protocols/src/types/index.ts
index cedefa7..2d75845 100644
--- a/packages/protocols/src/types/index.ts
+++ b/packages/protocols/src/types/index.ts
@@ -16,10 +16,10 @@ export type FullProof = {
 export type SolidityProof = StrBigInt[]
 
 export type SemaphoreWitness = {
-  identity_nullifier: StrBigInt
-  identity_trapdoor: StrBigInt
-  path_elements: StrBigInt[]
-  identity_path_index: number[]
-  external_nullifier: StrBigInt
-  signal_hash: StrBigInt
+  identityNullifier: StrBigInt
+  identityTrapdoor: StrBigInt
+  treeSiblings: StrBigInt[]
+  treePathIndices: number[]
+  externalNullifier: StrBigInt
+  signalHash: StrBigInt
 }
diff --git a/packages/protocols/src/utils.ts b/packages/protocols/src/utils.ts
index 3b63c83..2ff9f6d 100644
--- a/packages/protocols/src/utils.ts
+++ b/packages/protocols/src/utils.ts
@@ -72,5 +72,12 @@ export function generateMerkleProof(
     throw new Error("The leaf does not exists")
   }
 
-  return tree.createProof(leafIndex)
+  const merkleProof = tree.createProof(leafIndex)
+
+  if (arity === 2) {
+    // It makes it compatible with the parameter in the contracts.
+    merkleProof.siblings = merkleProof.siblings.map((s) => s[0])
+  }
+
+  return merkleProof
 }
diff --git a/packages/protocols/tests/semaphore.test.ts b/packages/protocols/tests/semaphore.test.ts
index 373a6dc..29f27ea 100644
--- a/packages/protocols/tests/semaphore.test.ts
+++ b/packages/protocols/tests/semaphore.test.ts
@@ -26,7 +26,7 @@ describe("Semaphore", () => {
       const leaves = [BigInt(3), BigInt(2), identityCommitment, BigInt(4)]
       const signal = "0x111"
 
-      const merkleProof = generateMerkleProof(20, BigInt(0), 5, leaves, identityCommitment)
+      const merkleProof = generateMerkleProof(20, BigInt(0), 2, leaves, identityCommitment)
 
       const witness = Semaphore.genWitness(
         identity.getTrapdoor(),
@@ -47,7 +47,7 @@ describe("Semaphore", () => {
       const leaves = [BigInt(3), BigInt(2), identityCommitment, BigInt(4)]
       const signal = "0x111"
 
-      const merkleProof = generateMerkleProof(20, BigInt(0), 5, leaves, identityCommitment)
+      const merkleProof = generateMerkleProof(20, BigInt(0), 2, leaves, identityCommitment)
 
       const witness = Semaphore.genWitness(
         identity.getTrapdoor(),
diff --git a/packages/protocols/zkeyFiles.zip.REMOVED.git-id b/packages/protocols/zkeyFiles.zip.REMOVED.git-id
index a3a7d2f..e8f0da3 100644
--- a/packages/protocols/zkeyFiles.zip.REMOVED.git-id
+++ b/packages/protocols/zkeyFiles.zip.REMOVED.git-id
@@ -1 +1 @@
-2daec67f953ad6155f56d4c0c16ac1b67eb97a94
\ No newline at end of file
+83a3802ca5e94bb251704b767deab0b7202c3ecd
\ No newline at end of file