Example using a private key generated from the Suapp (#50)

* Example using a private key generated from the Suapp

* Fix

Makefile

@@ -56,4 +56,5 @@ run-integration:
 	go run examples/private-library/main.go
 	go run examples/private-library-confidential-store/main.go
 	go run examples/private-suapp-key/main.go
+	go run examples/private-suapp-key-gen/main.go
 	go run examples/std-transaction-signing/main.go

examples/private-suapp-key-gen/README.md

@@ -0,0 +1,17 @@
+# Example Suapp with a stored private key generated by the Suapp
+
+This is a variation of the [private-suapp-key](../private-suapp-key) example. The difference is that the private key is generated by the Suapp itself during the `initialize` function.
+
+## How to use
+
+Run `Suave` in development mode:
+
+```
+$ suave --suave.dev
+```
+
+Execute the deployment script:
+
+```
+$ go run main.go
+```

examples/private-suapp-key-gen/main.go

@@ -0,0 +1,22 @@
+package main
+
+import (
+	"log"
+
+	"github.com/flashbots/suapp-examples/framework"
+)
+
+func main() {
+	fr := framework.New()
+
+	contract := fr.Suave.DeployContract("private-suapp-key-gen.sol/PublicSuapp.json")
+
+	contract.SendConfidentialRequest("initialize", nil, nil)
+	receipt := contract.SendConfidentialRequest("example", nil, nil)
+
+	// validate the signature (TODO: return the address from the Suapp and validate the signature)
+	_, err := contract.Abi.Events["TxnSignature"].ParseLog(receipt.Logs[0])
+	if err != nil {
+		log.Fatal(err)
+	}
+}

examples/private-suapp-key-gen/private-suapp-key-gen.sol

@@ -0,0 +1,53 @@
+// SPDX-License-Identifier: Unlicensed
+pragma solidity ^0.8.8;
+
+import "suave-std/suavelib/Suave.sol";
+import "suave-std/Context.sol";
+import "suave-std/Suapp.sol";
+import "suave-std/Transactions.sol";
+
+contract PublicSuapp is Suapp {
+    Suave.DataId signingKeyBid;
+    string public KEY_PRIVATE_KEY = "KEY";
+
+    // onchain-offchain pattern to register the new private key in the Confidential storage
+    function updateKeyCallback(Suave.DataId _signingKeyBid) public {
+        signingKeyBid = _signingKeyBid;
+    }
+
+    function initialize() public returns (bytes memory) {
+        string memory keyData = Suave.privateKeyGen(Suave.CryptoSignature.SECP256);
+
+        address[] memory peekers = new address[](1);
+        peekers[0] = address(this);
+
+        Suave.DataRecord memory bid = Suave.newDataRecord(10, peekers, peekers, "private_key");
+        Suave.confidentialStore(bid.id, KEY_PRIVATE_KEY, abi.encodePacked(keyData));
+
+        return abi.encodeWithSelector(this.updateKeyCallback.selector, bid.id);
+    }
+
+    // offchain-onchain pattern to sign a transaction using the private key stored in the Suapp
+    event TxnSignature(bytes32 r, bytes32 s);
+
+    function exampleCallback() public emitOffchainLogs {}
+
+    function example() public returns (bytes memory) {
+        bytes memory signingKey = Suave.confidentialRetrieve(signingKeyBid, KEY_PRIVATE_KEY);
+
+        Transactions.EIP155Request memory txnWithToAddress = Transactions.EIP155Request({
+            to: address(0x00000000000000000000000000000000DeaDBeef),
+            gas: 1000000,
+            gasPrice: 500,
+            value: 1,
+            nonce: 1,
+            data: bytes(""),
+            chainId: 1337
+        });
+
+        Transactions.EIP155 memory txn = Transactions.signTxn(txnWithToAddress, string(signingKey));
+        emit TxnSignature(txn.r, txn.s);
+
+        return abi.encodeWithSelector(this.exampleCallback.selector);
+    }
+}