From c117500761e2bb01a289705dd85a998d4504e3e6 Mon Sep 17 00:00:00 2001
From: Ferran Borreguero <ferran.borreguero@gmail.com>
Date: Tue, 26 Mar 2024 12:47:57 +0000
Subject: [PATCH] Add example of a suapp storing and using a private key

---
 examples/private-suapp-key/README.md          | 17 ++++++
 examples/private-suapp-key/main.go            | 33 ++++++++++++
 .../private-suapp-key/private-suapp-key.sol   | 53 +++++++++++++++++++
 3 files changed, 103 insertions(+)
 create mode 100644 examples/private-suapp-key/README.md
 create mode 100644 examples/private-suapp-key/main.go
 create mode 100644 examples/private-suapp-key/private-suapp-key.sol

diff --git a/examples/private-suapp-key/README.md b/examples/private-suapp-key/README.md
new file mode 100644
index 0000000..ff470c7
--- /dev/null
+++ b/examples/private-suapp-key/README.md
@@ -0,0 +1,17 @@
+# Example Suapp with a stored private key
+
+This example shows how Suapps can store private keys in the confidential storage to be used in multiple confidential requests.
+
+## How to use
+
+Run `Suave` in development mode:
+
+```
+$ suave --suave.dev
+```
+
+Execute the deployment script:
+
+```
+$ go run main.go
+```
diff --git a/examples/private-suapp-key/main.go b/examples/private-suapp-key/main.go
new file mode 100644
index 0000000..e7f9e62
--- /dev/null
+++ b/examples/private-suapp-key/main.go
@@ -0,0 +1,33 @@
+package main
+
+import (
+	"encoding/hex"
+	"log"
+
+	"github.com/flashbots/suapp-examples/framework"
+)
+
+func main() {
+	fr := framework.New()
+
+	priv := "b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291"
+
+	contract := fr.Suave.DeployContract("private-suapp-key.sol/PublicSuapp.json")
+	contract.SendConfidentialRequest("registerPrivateKey", nil, []byte(priv))
+
+	receipt := contract.SendConfidentialRequest("example", nil, nil)
+
+	// validate the signature
+	txnSignatureEvent, err := contract.Abi.Events["TxnSignature"].ParseLog(receipt.Logs[0])
+	if err != nil {
+		log.Fatal(err)
+	}
+	var r, s = txnSignatureEvent["r"].([32]byte), txnSignatureEvent["s"].([32]byte)
+
+	if hex.EncodeToString(r[:]) != "eebcfac0def6db5649d0ae6b52ed3b8ba1f5c6c428588df125461113ba8c6749" {
+		log.Fatal("wrong r signature")
+	}
+	if hex.EncodeToString(s[:]) != "5d5e1aafa0c964b43c251b6a525d49572968f2cebc5868c58bcc9281b9a07505" {
+		log.Fatal("wrong s signature")
+	}
+}
diff --git a/examples/private-suapp-key/private-suapp-key.sol b/examples/private-suapp-key/private-suapp-key.sol
new file mode 100644
index 0000000..7ae1a10
--- /dev/null
+++ b/examples/private-suapp-key/private-suapp-key.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 registerPrivateKey() public returns (bytes memory) {
+        bytes memory keyData = Context.confidentialInputs();
+
+        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, 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);
+    }
+}