From 88cc3698b3663972cd9b60faf5c14a7e1bbee965 Mon Sep 17 00:00:00 2001
From: Determinant <tederminant@gmail.com>
Date: Thu, 13 Aug 2020 21:11:56 -0400
Subject: WIP: X-to-C transfer

---
 plugin/evm/atomic_tx.go | 64 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100644 plugin/evm/atomic_tx.go

(limited to 'plugin/evm/atomic_tx.go')

diff --git a/plugin/evm/atomic_tx.go b/plugin/evm/atomic_tx.go
new file mode 100644
index 0000000..e8e48f7
--- /dev/null
+++ b/plugin/evm/atomic_tx.go
@@ -0,0 +1,64 @@
+// (c) 2019-2020, Ava Labs, Inc. All rights reserved.
+// See the file LICENSE for licensing terms.
+
+package evm
+
+import (
+	"fmt"
+
+	"github.com/ava-labs/gecko/database"
+	"github.com/ava-labs/gecko/ids"
+	"github.com/ava-labs/gecko/utils/crypto"
+	"github.com/ava-labs/gecko/utils/hashing"
+	"github.com/ava-labs/gecko/vms/components/verify"
+	"github.com/ava-labs/gecko/vms/secp256k1fx"
+)
+
+// UnsignedAtomicTx ...
+type UnsignedAtomicTx interface {
+	initialize(vm *VM, bytes []byte) error
+	ID() ids.ID
+	// UTXOs this tx consumes
+	InputUTXOs() ids.Set
+	// Attempts to verify this transaction with the provided state.
+	SemanticVerify(db database.Database, creds []verify.Verifiable) TxError
+	Accept(database.Batch) error
+}
+
+// AtomicTx is an operation that can be decided without being proposed, but must
+// have special control over database commitment
+type AtomicTx struct {
+	UnsignedAtomicTx `serialize:"true"`
+	// Credentials that authorize the inputs to be spent
+	Credentials []verify.Verifiable `serialize:"true" json:"credentials"`
+}
+
+func (vm *VM) signAtomicTx(tx *AtomicTx, signers [][]*crypto.PrivateKeySECP256K1R) error {
+	unsignedBytes, err := vm.codec.Marshal(tx.UnsignedAtomicTx)
+	if err != nil {
+		return fmt.Errorf("couldn't marshal UnsignedAtomicTx: %w", err)
+	}
+
+	// Attach credentials
+	hash := hashing.ComputeHash256(unsignedBytes)
+	tx.Credentials = make([]verify.Verifiable, len(signers))
+	for i, credKeys := range signers {
+		cred := &secp256k1fx.Credential{
+			Sigs: make([][crypto.SECP256K1RSigLen]byte, len(credKeys)),
+		}
+		for j, key := range credKeys {
+			sig, err := key.SignHash(hash) // Sign hash
+			if err != nil {
+				return fmt.Errorf("problem generating credential: %w", err)
+			}
+			copy(cred.Sigs[j][:], sig)
+		}
+		tx.Credentials[i] = cred // Attach credential
+	}
+
+	txBytes, err := vm.codec.Marshal(tx)
+	if err != nil {
+		return fmt.Errorf("couldn't marshal AtomicTx: %w", err)
+	}
+	return tx.initialize(vm, txBytes)
+}
-- 
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