Move subtle.go to its own package

subtle/subtle.go

@@ -0,0 +1,33 @@
+package subtle
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+
+	"golang.org/x/crypto/scrypt"
+)
+
+// EncryptWithoutIntegrity encrypts data with AES-CTR. Note: this encryption
+// mode is not secure when stored/sent on an untrusted medium.
+func EncryptWithoutIntegrity(key, input, iv []byte) (output []byte, err error) {
+	var block cipher.Block
+	if block, err = aes.NewCipher(key); err != nil {
+		return
+	}
+	output = make([]byte, len(input))
+	stream := cipher.NewCTR(block, iv)
+	stream.XORKeyStream(output, input)
+	return
+}
+
+// DecryptWithoutIntegrity decrypts data encrypted with AES-CTR.
+func DecryptWithoutIntegrity(key, input, iv []byte) ([]byte, error) {
+	// AES-CTR decryption is identical to encryption.
+	return EncryptWithoutIntegrity(key, input, iv)
+}
+
+// DeriveKey derives a key from a password using scrypt. N should be set to the
+// highest power of 2 you can derive within 100 milliseconds.
+func DeriveKey(password string, salt []byte, N int) ([]byte, error) {
+	return scrypt.Key([]byte(password), salt, N, 8, 1, 32)
+}

subtle/subtle_test.go

@@ -0,0 +1,31 @@
+package subtle
+
+import (
+	"github.com/stretchr/testify/assert"
+	"encoding/hex"
+	"testing"
+)
+
+func TestSubtle_EncryptWithoutIntegrity(t *testing.T) {
+	key, _ := hex.DecodeString("9469cccfc8a8d005247f39fa3e5b35a97db456cecf18deac6d84364d0818d763")
+	plaintext := []byte("some plaintext")
+	iv, _ := hex.DecodeString("c828f258a76aad7bc828f258a76aad7b")
+
+	ciphertext, _ := EncryptWithoutIntegrity(key, plaintext, iv)
+	assert.Exactly(t, "14697192f7e112fc88d83380693f", hex.EncodeToString(ciphertext))
+}
+
+func TestSubtle_DecryptWithoutIntegrity(t *testing.T) {
+	key, _ := hex.DecodeString("9469cccfc8a8d005247f39fa3e5b35a97db456cecf18deac6d84364d0818d763")
+	ciphertext, _ := hex.DecodeString("14697192f7e112fc88d83380693f")
+	iv, _ := hex.DecodeString("c828f258a76aad7bc828f258a76aad7b")
+
+	plaintext, _ := DecryptWithoutIntegrity(key, ciphertext, iv)
+	assert.Exactly(t, "some plaintext", string(plaintext))
+}
+
+func TestSubtle_DeriveKey(t *testing.T) {
+	salt, _ := hex.DecodeString("c828f258a76aad7b")
+	dk, _ := DeriveKey("some password", salt, 32768)
+	assert.Exactly(t, "9469cccfc8a8d005247f39fa3e5b35a97db456cecf18deac6d84364d0818d763", hex.EncodeToString(dk))
+}