swarm: codebase split from go-ethereum (#1405)

api/encrypt.go

@@ -0,0 +1,78 @@
+// Copyright 2016 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 api
+
+import (
+	"encoding/binary"
+	"errors"
+
+	"github.com/ethersphere/swarm/storage/encryption"
+	"golang.org/x/crypto/sha3"
+)
+
+type RefEncryption struct {
+	refSize int
+	span    []byte
+}
+
+func NewRefEncryption(refSize int) *RefEncryption {
+	span := make([]byte, 8)
+	binary.LittleEndian.PutUint64(span, uint64(refSize))
+	return &RefEncryption{
+		refSize: refSize,
+		span:    span,
+	}
+}
+
+func (re *RefEncryption) Encrypt(ref []byte, key []byte) ([]byte, error) {
+	spanEncryption := encryption.New(key, 0, uint32(re.refSize/32), sha3.NewLegacyKeccak256)
+	encryptedSpan, err := spanEncryption.Encrypt(re.span)
+	if err != nil {
+		return nil, err
+	}
+	dataEncryption := encryption.New(key, re.refSize, 0, sha3.NewLegacyKeccak256)
+	encryptedData, err := dataEncryption.Encrypt(ref)
+	if err != nil {
+		return nil, err
+	}
+	encryptedRef := make([]byte, len(ref)+8)
+	copy(encryptedRef[:8], encryptedSpan)
+	copy(encryptedRef[8:], encryptedData)
+
+	return encryptedRef, nil
+}
+
+func (re *RefEncryption) Decrypt(ref []byte, key []byte) ([]byte, error) {
+	spanEncryption := encryption.New(key, 0, uint32(re.refSize/32), sha3.NewLegacyKeccak256)
+	decryptedSpan, err := spanEncryption.Decrypt(ref[:8])
+	if err != nil {
+		return nil, err
+	}
+
+	size := binary.LittleEndian.Uint64(decryptedSpan)
+	if size != uint64(len(ref)-8) {
+		return nil, errors.New("invalid span in encrypted reference")
+	}
+
+	dataEncryption := encryption.New(key, re.refSize, 0, sha3.NewLegacyKeccak256)
+	decryptedRef, err := dataEncryption.Decrypt(ref[8:])
+	if err != nil {
+		return nil, err
+	}
+
+	return decryptedRef, nil
+}