diff options
Diffstat (limited to 'swarm/storage/encryption/encryption.go')
-rw-r--r-- | swarm/storage/encryption/encryption.go | 126 |
1 files changed, 81 insertions, 45 deletions
diff --git a/swarm/storage/encryption/encryption.go b/swarm/storage/encryption/encryption.go index e50f2163d..6fbdab062 100644 --- a/swarm/storage/encryption/encryption.go +++ b/swarm/storage/encryption/encryption.go @@ -21,6 +21,7 @@ import ( "encoding/binary" "fmt" "hash" + "sync" ) const KeyLength = 32 @@ -28,84 +29,119 @@ const KeyLength = 32 type Key []byte type Encryption interface { - Encrypt(data []byte, key Key) ([]byte, error) - Decrypt(data []byte, key Key) ([]byte, error) + Encrypt(data []byte) ([]byte, error) + Decrypt(data []byte) ([]byte, error) } type encryption struct { - padding int - initCtr uint32 - hashFunc func() hash.Hash + key Key // the encryption key (hashSize bytes long) + keyLen int // length of the key = length of blockcipher block + padding int // encryption will pad the data upto this if > 0 + initCtr uint32 // initial counter used for counter mode blockcipher + hashFunc func() hash.Hash // hasher constructor function } -func New(padding int, initCtr uint32, hashFunc func() hash.Hash) *encryption { +// New constructs a new encryptor/decryptor +func New(key Key, padding int, initCtr uint32, hashFunc func() hash.Hash) *encryption { return &encryption{ + key: key, + keyLen: len(key), padding: padding, initCtr: initCtr, hashFunc: hashFunc, } } -func (e *encryption) Encrypt(data []byte, key Key) ([]byte, error) { +// Encrypt encrypts the data and does padding if specified +func (e *encryption) Encrypt(data []byte) ([]byte, error) { length := len(data) + outLength := length isFixedPadding := e.padding > 0 - if isFixedPadding && length > e.padding { - return nil, fmt.Errorf("Data length longer than padding, data length %v padding %v", length, e.padding) - } - - paddedData := data - if isFixedPadding && length < e.padding { - paddedData = make([]byte, e.padding) - copy(paddedData[:length], data) - rand.Read(paddedData[length:]) + if isFixedPadding { + if length > e.padding { + return nil, fmt.Errorf("Data length longer than padding, data length %v padding %v", length, e.padding) + } + outLength = e.padding } - return e.transform(paddedData, key), nil + out := make([]byte, outLength) + e.transform(data, out) + return out, nil } -func (e *encryption) Decrypt(data []byte, key Key) ([]byte, error) { +// Decrypt decrypts the data, if padding was used caller must know original length and truncate +func (e *encryption) Decrypt(data []byte) ([]byte, error) { length := len(data) if e.padding > 0 && length != e.padding { return nil, fmt.Errorf("Data length different than padding, data length %v padding %v", length, e.padding) } + out := make([]byte, length) + e.transform(data, out) + return out, nil +} - return e.transform(data, key), nil +// +func (e *encryption) transform(in, out []byte) { + inLength := len(in) + wg := sync.WaitGroup{} + wg.Add((inLength-1)/e.keyLen + 1) + for i := 0; i < inLength; i += e.keyLen { + l := min(e.keyLen, inLength-i) + // call transformations per segment (asyncronously) + go func(i int, x, y []byte) { + defer wg.Done() + e.Transcrypt(i, x, y) + }(i/e.keyLen, in[i:i+l], out[i:i+l]) + } + // pad the rest if out is longer + pad(out[inLength:]) + wg.Wait() } -func (e *encryption) transform(data []byte, key Key) []byte { - dataLength := len(data) - transformedData := make([]byte, dataLength) +// used for segmentwise transformation +// if in is shorter than out, padding is used +func (e *encryption) Transcrypt(i int, in []byte, out []byte) { + // first hash key with counter (initial counter + i) hasher := e.hashFunc() - ctr := e.initCtr - hashSize := hasher.Size() - for i := 0; i < dataLength; i += hashSize { - hasher.Write(key) + hasher.Write(e.key) - ctrBytes := make([]byte, 4) - binary.LittleEndian.PutUint32(ctrBytes, ctr) + ctrBytes := make([]byte, 4) + binary.LittleEndian.PutUint32(ctrBytes, uint32(i)+e.initCtr) + hasher.Write(ctrBytes) - hasher.Write(ctrBytes) + ctrHash := hasher.Sum(nil) + hasher.Reset() - ctrHash := hasher.Sum(nil) - hasher.Reset() - hasher.Write(ctrHash) + // second round of hashing for selective disclosure + hasher.Write(ctrHash) + segmentKey := hasher.Sum(nil) + hasher.Reset() - segmentKey := hasher.Sum(nil) - - hasher.Reset() + // XOR bytes uptil length of in (out must be at least as long) + inLength := len(in) + for j := 0; j < inLength; j++ { + out[j] = in[j] ^ segmentKey[j] + } + // insert padding if out is longer + pad(out[inLength:]) +} - segmentSize := min(hashSize, dataLength-i) - for j := 0; j < segmentSize; j++ { - transformedData[i+j] = data[i+j] ^ segmentKey[j] - } - ctr++ +func pad(b []byte) { + l := len(b) + for total := 0; total < l; { + read, _ := rand.Read(b[total:]) + total += read } - return transformedData } -func GenerateRandomKey() (Key, error) { - key := make([]byte, KeyLength) - _, err := rand.Read(key) - return key, err +// GenerateRandomKey generates a random key of length l +func GenerateRandomKey(l int) Key { + key := make([]byte, l) + var total int + for total < l { + read, _ := rand.Read(key[total:]) + total += read + } + return key } func min(x, y int) int { |