Remove TFHE.req (#121)

* fix(lib): remove requires

* fix(contracts): remove use of `TFHE.req`

codegen/common.ts

@@ -37,7 +37,6 @@ export const ALL_PRECOMPILES: Precompile[] = [
   { name: 'Verify', code: 66 },
   { name: 'Reencrypt', code: 67 },
   { name: 'FhePubKey', code: 68 },
-  { name: 'Require', code: 69 },
   { name: 'LessThanOrEqual', code: 70 },
   { name: 'Subtract', code: 71 },
   { name: 'Multiply', code: 72 },

codegen/templates.ts

@@ -446,12 +446,6 @@ function unaryOperatorImpl(op: Operator): string {
 
 function tfheCustomMethods(): string {
   return `
-    // Require that the encrypted bool 'b' is true.
-    // Involves decrypting 'b'.
-    function req(ebool b) internal view {
-        Impl.req(ebool.unwrap(b));
-    }
-
     // Optimistically require that 'b' is true.
     //
     // This function does not evaluate 'b' at the time of the call.
@@ -461,10 +455,11 @@ function tfheCustomMethods(): string {
     // gas cost, as if all optimistic requires were true. Yet, the transaction will be
     // reverted at the end if any of the optimisic requires were false.
     //
-    // Exceptions to above rule are encrypted requires via TFHE.req() and decryption via
-    // TFHE.decrypt(). If either of them are encountered and if optimistic requires have been
-    // used before in the txn, the optimisic requires will be immediately evaluated. Rationale is
-    // that we want to avoid decrypting a non-optimistic require or a value if the txn is about
+    // Exceptions to above rule are reencryptions and decryptions via
+    // TFHE.reencrypt() and TFHE.decrypt(), respectively. If either of them
+    // are encountered and if optimistic requires have been used before in the
+    // txn, the optimisic requires will be immediately evaluated. Rationale is
+    // that we want to avoid decrypting or reencrypting a value if the txn is about
     // to fail and be reverted anyway at the end. Checking immediately and reverting on the spot
     // would avoid unnecessary decryptions.
     //
@@ -692,20 +687,6 @@ function implCustomMethods(): string {
         result = uint256(output[0]);
     }
 
-    function req(uint256 ciphertext) internal view {
-        bytes32[1] memory input;
-        input[0] = bytes32(ciphertext);
-        uint256 inputLen = 32;
-
-        // Call the require precompile.
-        uint256 precompile = Precompiles.Require;
-        assembly {
-            if iszero(staticcall(gas(), precompile, input, inputLen, 0, 0)) {
-                revert(0, 0)
-            }
-        }
-    }
-
     function decrypt(uint256 ciphertext) internal view returns(uint256 result) {
         bytes32[1] memory input;
         input[0] = bytes32(ciphertext);

contracts/BlindAuction.sol

@@ -118,7 +118,7 @@ contract BlindAuction is EIP712WithModifier {
     // Claim the object. Succeeds only if the caller has the highest bid.
     function claim() public onlyAfterEnd {
         require(!objectClaimed);
-        TFHE.req(TFHE.le(highestBid, bids[msg.sender]));
+        require(TFHE.decrypt(TFHE.le(highestBid, bids[msg.sender])));
 
         objectClaimed = true;
         bids[msg.sender] = TFHE.NIL32;
@@ -137,7 +137,7 @@ contract BlindAuction is EIP712WithModifier {
     function withdraw() public onlyAfterEnd {
         euint32 bidValue = bids[msg.sender];
         if (!objectClaimed) {
-            TFHE.req(TFHE.lt(bidValue, highestBid));
+            require(TFHE.decrypt(TFHE.lt(bidValue, highestBid)));
         }
         tokenContract.transfer(msg.sender, bidValue);
         bids[msg.sender] = TFHE.NIL32;

contracts/EncryptedERC20.sol

@@ -104,14 +104,14 @@ contract EncryptedERC20 is EIP712WithModifier {
 
     function _updateAllowance(address owner, address spender, euint32 amount) internal {
         euint32 currentAllowance = _allowance(owner, spender);
-        TFHE.req(TFHE.le(amount, currentAllowance));
+        require(TFHE.decrypt(TFHE.le(amount, currentAllowance)));
         _approve(owner, spender, TFHE.sub(currentAllowance, amount));
     }
 
     // Transfers an encrypted amount.
     function _transfer(address from, address to, euint32 amount) internal {
         // Make sure the sender has enough tokens.
-        TFHE.req(TFHE.le(amount, balances[from]));
+        require(TFHE.decrypt(TFHE.le(amount, balances[from])));
 
         // Add to the balance of `to` and subract from the balance of `from`.
         balances[to] = TFHE.add(balances[to], amount);

contracts/OptimisticRequire.sol

@@ -60,10 +60,10 @@ contract OptimisticRequire {
     // Charge less than full gas, because the non-optimistic ciphertext require aborts early.
     function reqFalse() public {
         // True.
-        TFHE.req(TFHE.le(ct1, ct2));
+        require(TFHE.decrypt(TFHE.le(ct1, ct2)));
 
         // False.
-        TFHE.req(TFHE.lt(ct1, ct2));
+        require(TFHE.decrypt(TFHE.lt(ct1, ct2)));
 
         // Try to mutate state to pay for gas - we won't reach that point due to the false require.
         doWorkToPayGas();

lib/Impl.sol

@@ -580,20 +580,6 @@ library Impl {
         result = uint256(output[0]);
     }
 
-    function req(uint256 ciphertext) internal view {
-        bytes32[1] memory input;
-        input[0] = bytes32(ciphertext);
-        uint256 inputLen = 32;
-
-        // Call the require precompile.
-        uint256 precompile = Precompiles.Require;
-        assembly {
-            if iszero(staticcall(gas(), precompile, input, inputLen, 0, 0)) {
-                revert(0, 0)
-            }
-        }
-    }
-
     function decrypt(uint256 ciphertext) internal view returns (uint256 result) {
         bytes32[1] memory input;
         input[0] = bytes32(ciphertext);

lib/Precompiles.sol

@@ -7,7 +7,6 @@ library Precompiles {
     uint256 public constant Verify = 66;
     uint256 public constant Reencrypt = 67;
     uint256 public constant FhePubKey = 68;
-    uint256 public constant Require = 69;
     uint256 public constant LessThanOrEqual = 70;
     uint256 public constant Subtract = 71;
     uint256 public constant Multiply = 72;

lib/TFHE.sol

@@ -2483,12 +2483,6 @@ library TFHE {
         return euint32.wrap(Impl.not(euint32.unwrap(value)));
     }
 
-    // Require that the encrypted bool 'b' is true.
-    // Involves decrypting 'b'.
-    function req(ebool b) internal view {
-        Impl.req(ebool.unwrap(b));
-    }
-
     // Optimistically require that 'b' is true.
     //
     // This function does not evaluate 'b' at the time of the call.
@@ -2498,10 +2492,10 @@ library TFHE {
     // gas cost, as if all optimistic requires were true. Yet, the transaction will be
     // reverted at the end if any of the optimisic requires were false.
     //
-    // Exceptions to above rule are encrypted requires via TFHE.req() and decryption via
+    // Exceptions to above rule are reencryptions and decryptions via
     // TFHE.decrypt(). If either of them are encountered and if optimistic requires have been
     // used before in the txn, the optimisic requires will be immediately evaluated. Rationale is
-    // that we want to avoid decrypting a non-optimistic require or a value if the txn is about
+    // that we want to avoid decrypting or reencrypting a value if the txn is about
     // to fail and be reverted anyway at the end. Checking immediately and reverting on the spot
     // would avoid unnecessary decryptions.
     //