diff --git a/docs/PROTOCOL_SPEC.md b/docs/PROTOCOL_SPEC.md
index 2ba04ed..436e7e2 100644
--- a/docs/PROTOCOL_SPEC.md
+++ b/docs/PROTOCOL_SPEC.md
@@ -44,9 +44,10 @@ Non-transferable identity token. One per address. Cannot be burned or transferre
 ### Mint Flow
 
 1. Controller sets `currentEulaHash` on the contract.
-2. User calls `mintSBT(encryptedAccountId, zkpCommitment, eulaHash)`.
-3. Contract verifies: no existing SBT for caller, valid account ID, EULA hash matches current.
-4. SBT is created. The transaction signature constitutes cryptographic EULA acceptance.
+2. User calls `mintSBT(zkpCommitment, eulaHash)`.
+3. Contract verifies: no existing SBT for caller, EULA hash matches current.
+4. Contract internally derives `encryptedAccountId` deterministically from `msg.sender` and `chainId` to enforce canonical identity derivation.
+5. SBT is created. The transaction signature constitutes cryptographic EULA acceptance.
 
 ### ZKP Commitment
 
@@ -306,4 +307,4 @@ The contracts are not upgradeable. There are no proxies and no `delegatecall`. T
 3. Users deposit to new DepositPool.
 4. Old ClaimPool operator processes remaining redemptions.
 
-This is intentional. Immutable contracts are auditable contracts.
\ No newline at end of file
+This is intentional. Immutable contracts are auditable contracts.
diff --git a/src/SoulBoundToken.sol b/src/SoulBoundToken.sol
index 9a97f76..1061bc9 100644
--- a/src/SoulBoundToken.sol
+++ b/src/SoulBoundToken.sol
@@ -92,22 +92,23 @@ contract SoulBoundToken is ISoulBoundToken {
 
     /**
      * @notice Mint SBT with EULA acceptance gate
-     * @param _encryptedAccountId Hashed account identifier
      * @param _zkpCommitment Privado ID ZKP commitment (can be bytes32(0) if not yet verified)
      * @param _eulaHash Must match currentEulaHash — the transaction signature IS the acceptance
+     * @dev _encryptedAccountId is the canonical identity derivation on-chain
      * @dev The act of calling this function with the correct EULA hash, signed by the user's
      *      wallet, constitutes cryptographic proof of EULA acceptance on an immutable ledger.
      */
     function mintSBT(
-        bytes32 _encryptedAccountId,
         bytes32 _zkpCommitment,
         bytes32 _eulaHash
     ) external {
         if (_sbtRegistry[msg.sender].exists) revert SBTAlreadyExists();
-        if (_encryptedAccountId == bytes32(0)) revert InvalidAccountId();
         if (currentEulaHash == bytes32(0)) revert EulaNotSet();
         if (_eulaHash != currentEulaHash) revert EulaMismatch();
 
+        bytes32 _encryptedAccountId = keccak256(abi.encodePacked(msg.sender, "SBF_ALPHA_V1", block.chainid));
+        
+
         _sbtRegistry[msg.sender] = SBTData({
             encryptedAccountId: _encryptedAccountId,
             zkpCommitment: _zkpCommitment,