From f8f07dbc70640b572dc7ffba13a9bed2c887c390 Mon Sep 17 00:00:00 2001
From: Aayush <arajasek94@gmail.com>
Date: Thu, 15 Dec 2022 16:39:12 -0500
Subject: [PATCH] Support creation and signing of Eth keys

---
 chain/types/ethtypes/eth_types.go |  2 +-
 chain/wallet/key/key.go           | 21 ++++++++++++++++++++-
 lib/sigs/delegated/init.go        | 12 ++++++++++--
 3 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/chain/types/ethtypes/eth_types.go b/chain/types/ethtypes/eth_types.go
index 6eefb5bf0..75846e10a 100644
--- a/chain/types/ethtypes/eth_types.go
+++ b/chain/types/ethtypes/eth_types.go
@@ -304,7 +304,7 @@ func EthAddressFromHex(s string) (EthAddress, error) {
 func EthAddressFromBytes(b []byte) (EthAddress, error) {
 	var a EthAddress
 	if len(b) != EthAddressLength {
-		return EthAddress{}, xerrors.Errorf("cannot parse bytes into anœ EthAddress: incorrect input length")
+		return EthAddress{}, xerrors.Errorf("cannot parse bytes into an EthAddress: incorrect input length")
 	}
 	copy(a[:], b[:])
 	return a, nil
diff --git a/chain/wallet/key/key.go b/chain/wallet/key/key.go
index cb769ef09..a52a431c6 100644
--- a/chain/wallet/key/key.go
+++ b/chain/wallet/key/key.go
@@ -1,9 +1,11 @@
 package key
 
 import (
+	"golang.org/x/crypto/sha3"
 	"golang.org/x/xerrors"
 
 	"github.com/filecoin-project/go-address"
+	"github.com/filecoin-project/go-state-types/builtin"
 	"github.com/filecoin-project/go-state-types/crypto"
 
 	"github.com/filecoin-project/lotus/chain/types"
@@ -45,11 +47,27 @@ func NewKey(keyinfo types.KeyInfo) (*Key, error) {
 	}
 
 	switch k.Type {
-	case types.KTSecp256k1, types.KTDelegated:
+	case types.KTSecp256k1:
 		k.Address, err = address.NewSecp256k1Address(k.PublicKey)
 		if err != nil {
 			return nil, xerrors.Errorf("converting Secp256k1 to address: %w", err)
 		}
+	case types.KTDelegated:
+		// Assume eth for now
+		hasher := sha3.NewLegacyKeccak256()
+		pubk := k.PublicKey
+		// if we get an uncompressed public key (that's what we get from the library,
+		// but putting this check here for defensiveness), strip the prefix
+		if pubk[0] == 0x04 {
+			pubk = pubk[1:]
+		}
+
+		hasher.Write(pubk)
+
+		k.Address, err = address.NewDelegatedAddress(builtin.EthereumAddressManagerActorID, hasher.Sum(nil)[12:])
+		if err != nil {
+			return nil, xerrors.Errorf("converting Delegated to address: %w", err)
+		}
 	case types.KTBLS:
 		k.Address, err = address.NewBLSAddress(k.PublicKey)
 		if err != nil {
@@ -58,6 +76,7 @@ func NewKey(keyinfo types.KeyInfo) (*Key, error) {
 	default:
 		return nil, xerrors.Errorf("unsupported key type: %s", k.Type)
 	}
+
 	return k, nil
 
 }
diff --git a/lib/sigs/delegated/init.go b/lib/sigs/delegated/init.go
index e092bc576..e25e8e9cb 100644
--- a/lib/sigs/delegated/init.go
+++ b/lib/sigs/delegated/init.go
@@ -27,8 +27,16 @@ func (delegatedSigner) ToPublic(pk []byte) ([]byte, error) {
 	return gocrypto.PublicKey(pk), nil
 }
 
-func (delegatedSigner) Sign(pk []byte, msg []byte) ([]byte, error) {
-	return nil, fmt.Errorf("not implemented")
+func (s delegatedSigner) Sign(pk []byte, msg []byte) ([]byte, error) {
+	hasher := sha3.NewLegacyKeccak256()
+	hasher.Write(msg)
+	hashSum := hasher.Sum(nil)
+	sig, err := gocrypto.Sign(pk, hashSum)
+	if err != nil {
+		return nil, err
+	}
+
+	return sig, nil
 }
 
 func (delegatedSigner) Verify(sig []byte, a address.Address, msg []byte) error {