1 files changed, 75 insertions, 0 deletions
diff --git a/swarm/storage/feeds/sign.go b/swarm/storage/feeds/sign.go
new file mode 100644
index 000000000..a69942f2b
--- /dev/null
+++ b/swarm/storage/feeds/sign.go
@@ -0,0 +1,75 @@
+// Copyright 2018 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package feeds
+
+import (
+	"crypto/ecdsa"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/crypto"
+)
+
+const signatureLength = 65
+
+// Signature is an alias for a static byte array with the size of a signature
+type Signature [signatureLength]byte
+
+// Signer signs Feed update payloads
+type Signer interface {
+	Sign(common.Hash) (Signature, error)
+	Address() common.Address
+}
+
+// GenericSigner implements the Signer interface
+// It is the vanilla signer that probably should be used in most cases
+type GenericSigner struct {
+	PrivKey *ecdsa.PrivateKey
+	address common.Address
+}
+
+// NewGenericSigner builds a signer that will sign everything with the provided private key
+func NewGenericSigner(privKey *ecdsa.PrivateKey) *GenericSigner {
+	return &GenericSigner{
+		PrivKey: privKey,
+		address: crypto.PubkeyToAddress(privKey.PublicKey),
+	}
+}
+
+// Sign signs the supplied data
+// It wraps the ethereum crypto.Sign() method
+func (s *GenericSigner) Sign(data common.Hash) (signature Signature, err error) {
+	signaturebytes, err := crypto.Sign(data.Bytes(), s.PrivKey)
+	if err != nil {
+		return
+	}
+	copy(signature[:], signaturebytes)
+	return
+}
+
+// Address returns the public key of the signer's private key
+func (s *GenericSigner) Address() common.Address {
+	return s.address
+}
+
+// getUserAddr extracts the address of the Feed update signer
+func getUserAddr(digest common.Hash, signature Signature) (common.Address, error) {
+	pub, err := crypto.SigToPub(digest.Bytes(), signature[:])
+	if err != nil {
+		return common.Address{}, err
+	}
+	return crypto.PubkeyToAddress(*pub), nil
+}