diff --git a/programs/gateway/src/lib.rs b/programs/gateway/src/lib.rs
index f3e14c2..70b8b63 100644
--- a/programs/gateway/src/lib.rs
+++ b/programs/gateway/src/lib.rs
@@ -31,6 +31,15 @@ pub enum Errors {
     EmptyReceiver,
 }
 
+/// Enumeration for instruction identifiers in message hashes.
+#[repr(u8)]
+enum InstructionId {
+    Withdraw = 1,
+    WithdrawSplToken = 2,
+    WhitelistSplToken = 3,
+    UnwhitelistSplToken = 4,
+}
+
 declare_id!("ZETAjseVjuFsxdRxo6MmTCvqFwb3ZHUx56Co3vCmGis");
 
 #[program]
@@ -159,7 +168,7 @@ pub mod gateway {
                 signature,
                 recovery_id,
                 nonce,
-                "whitelist_spl_mint",
+                InstructionId::WhitelistSplToken as u8,
             )?;
         } else {
             require!(
@@ -202,7 +211,7 @@ pub mod gateway {
                 signature,
                 recovery_id,
                 nonce,
-                "unwhitelist_spl_mint",
+                InstructionId::UnwhitelistSplToken as u8,
             )?;
         } else {
             require!(
@@ -377,7 +386,8 @@ pub mod gateway {
         }
 
         let mut concatenated_buffer = Vec::new();
-        concatenated_buffer.extend_from_slice("withdraw".as_bytes());
+        concatenated_buffer.extend_from_slice(b"ZETACHAIN");
+        concatenated_buffer.push(InstructionId::Withdraw as u8);
         concatenated_buffer.extend_from_slice(&pda.chain_id.to_be_bytes());
         concatenated_buffer.extend_from_slice(&nonce.to_be_bytes());
         concatenated_buffer.extend_from_slice(&amount.to_be_bytes());
@@ -435,7 +445,8 @@ pub mod gateway {
         }
 
         let mut concatenated_buffer = Vec::new();
-        concatenated_buffer.extend_from_slice("withdraw_spl_token".as_bytes());
+        concatenated_buffer.extend_from_slice(b"ZETACHAIN");
+        concatenated_buffer.push(InstructionId::WithdrawSplToken as u8);
         concatenated_buffer.extend_from_slice(&pda.chain_id.to_be_bytes());
         concatenated_buffer.extend_from_slice(&nonce.to_be_bytes());
         concatenated_buffer.extend_from_slice(&amount.to_be_bytes());
@@ -581,7 +592,7 @@ fn validate_whitelist_tss_signature(
     signature: [u8; 64],
     recovery_id: u8,
     nonce: u64,
-    instruction_name: &str,
+    instruction: u8,
 ) -> Result<()> {
     if nonce != pda.nonce {
         msg!(
@@ -593,10 +604,11 @@ fn validate_whitelist_tss_signature(
     }
 
     let mut concatenated_buffer = Vec::new();
-    concatenated_buffer.extend_from_slice(instruction_name.as_bytes());
+    concatenated_buffer.extend_from_slice(b"ZETACHAIN");
+    concatenated_buffer.push(instruction);
     concatenated_buffer.extend_from_slice(&pda.chain_id.to_be_bytes());
-    concatenated_buffer.extend_from_slice(&whitelist_candidate.key().to_bytes());
     concatenated_buffer.extend_from_slice(&nonce.to_be_bytes());
+    concatenated_buffer.extend_from_slice(&whitelist_candidate.key().to_bytes());
     let computed_message_hash = hash(&concatenated_buffer[..]).to_bytes();
 
     msg!("Computed message hash: {:?}", computed_message_hash);
diff --git a/tests/gateway.ts b/tests/gateway.ts
index 2a3e5fa..4c20590 100644
--- a/tests/gateway.ts
+++ b/tests/gateway.ts
@@ -96,7 +96,8 @@ async function withdrawSplToken(
   gatewayProgram: Program<Gateway>
 ) {
   const buffer = Buffer.concat([
-    Buffer.from("withdraw_spl_token", "utf-8"),
+    Buffer.from("ZETACHAIN", "utf-8"),
+    Buffer.from([0x02]),
     chain_id_bn.toArrayLike(Buffer, "be", 8),
     nonce.toArrayLike(Buffer, "be", 8),
     amount.toArrayLike(Buffer, "be", 8),
@@ -373,7 +374,8 @@ describe("Gateway", () => {
     try {
       const nonce2 = nonce.addn(1);
       const buffer = Buffer.concat([
-        Buffer.from("withdraw_spl_token", "utf-8"),
+        Buffer.from("ZETACHAIN", "utf-8"),
+        Buffer.from([0x02]),
         chain_id_bn.toArrayLike(Buffer, "be", 8),
         nonce2.toArrayLike(Buffer, "be", 8),
         amount.toArrayLike(Buffer, "be", 8),
@@ -438,7 +440,8 @@ describe("Gateway", () => {
       wallet.publicKey
     );
     const buffer = Buffer.concat([
-      Buffer.from("withdraw", "utf-8"),
+      Buffer.from("ZETACHAIN", "utf-8"),
+      Buffer.from([0x01]),
       chain_id_bn.toArrayLike(Buffer, "be", 8),
       nonce.toArrayLike(Buffer, "be", 8),
       amount.toArrayLike(Buffer, "be", 8),
@@ -479,7 +482,8 @@ describe("Gateway", () => {
     );
 
     const buffer = Buffer.concat([
-      Buffer.from("withdraw", "utf-8"),
+      Buffer.from("ZETACHAIN", "utf-8"),
+      Buffer.from([0x01]),
       chain_id_bn.toArrayLike(Buffer, "be", 8),
       nonce.toArrayLike(Buffer, "be", 8),
       amount.toArrayLike(Buffer, "be", 8),
@@ -522,7 +526,8 @@ describe("Gateway", () => {
     );
 
     const buffer = Buffer.concat([
-      Buffer.from("withdraw", "utf-8"),
+      Buffer.from("ZETACHAIN", "utf-8"),
+      Buffer.from([0x01]),
       chain_id_bn.toArrayLike(Buffer, "be", 8),
       nonce.subn(1).toArrayLike(Buffer, "be", 8), // wrong nonce
       amount.toArrayLike(Buffer, "be", 8),
@@ -640,7 +645,8 @@ describe("Gateway", () => {
     );
 
     const buffer = Buffer.concat([
-      Buffer.from("withdraw_spl_token", "utf-8"),
+      Buffer.from("ZETACHAIN", "utf-8"),
+      Buffer.from([0x02]),
       chain_id_bn.toArrayLike(Buffer, "be", 8),
       nonce.subn(1).toArrayLike(Buffer, "be", 8), // wrong nonce
       amount.toArrayLike(Buffer, "be", 8),
@@ -754,10 +760,11 @@ describe("Gateway", () => {
     const nonce = pdaAccountData.nonce;
 
     const buffer = Buffer.concat([
-      Buffer.from("unwhitelist_spl_mint", "utf-8"),
+      Buffer.from("ZETACHAIN", "utf-8"),
+      Buffer.from([0x04]),
       chain_id_bn.toArrayLike(Buffer, "be", 8),
-      mint.publicKey.toBuffer(),
       nonce.toArrayLike(Buffer, "be", 8),
+      mint.publicKey.toBuffer(),
     ]);
     const message_hash = keccak256(buffer);
     const signature = keyPair.sign(message_hash, "hex");
@@ -792,10 +799,11 @@ describe("Gateway", () => {
     const nonce = pdaAccountData.nonce;
 
     const buffer = Buffer.concat([
-      Buffer.from("whitelist_spl_mint", "utf-8"),
+      Buffer.from("ZETACHAIN", "utf-8"),
+      Buffer.from([0x03]),
       chain_id_bn.toArrayLike(Buffer, "be", 8),
-      mint.publicKey.toBuffer(),
       nonce.toArrayLike(Buffer, "be", 8),
+      mint.publicKey.toBuffer(),
     ]);
     const message_hash = keccak256(buffer);
     const signature = keyPair.sign(message_hash, "hex");
@@ -823,10 +831,11 @@ describe("Gateway", () => {
     const nonce = pdaAccountData.nonce;
 
     const buffer = Buffer.concat([
-      Buffer.from("whitelist_spl_mint", "utf-8"),
+      Buffer.from("ZETACHAIN", "utf-8"),
+      Buffer.from([0x03]),
       chain_id_bn.toArrayLike(Buffer, "be", 8),
-      mint.publicKey.toBuffer(),
       nonce.subn(1).toArrayLike(Buffer, "be", 8), // wrong nonce
+      mint.publicKey.toBuffer(),
     ]);
     const message_hash = keccak256(buffer);
     const signature = keyPair.sign(message_hash, "hex");
@@ -858,10 +867,11 @@ describe("Gateway", () => {
     const nonce = pdaAccountData.nonce;
 
     const buffer = Buffer.concat([
-      Buffer.from("whitelist_spl_mint", "utf-8"),
+      Buffer.from("ZETACHAIN", "utf-8"),
+      Buffer.from([0x03]),
       chain_id_bn.toArrayLike(Buffer, "be", 8),
+      nonce.toArrayLike(Buffer, "be", 8),
       mint.publicKey.toBuffer(),
-      nonce.toArrayLike(Buffer, "be", 8), // wrong nonce
     ]);
     const message_hash = keccak256(buffer);
     const signature = keyPair.sign(message_hash, "hex");