add crypto pkg and DeriveKey func

globalplatform/crypto/crypto.go

@@ -0,0 +1,39 @@
+package crypto
+
+import (
+	"crypto/cipher"
+	"crypto/des"
+)
+
+var (
+	DerivationPurposeEnc = []byte{0x01, 0x82}
+	nullBytes8           = []byte{0, 0, 0, 0, 0, 0, 0, 0}
+)
+
+func DeriveKey(cardKey []byte, seq []byte, purpose []byte) ([]byte, error) {
+	key24 := resizeKey24(cardKey)
+
+	derivation := make([]byte, 16)
+	copy(derivation, purpose[:2])
+	copy(derivation[2:], seq[:2])
+
+	block, err := des.NewTripleDESCipher(key24)
+	if err != nil {
+		return nil, err
+	}
+
+	ciphertext := make([]byte, 16)
+
+	mode := cipher.NewCBCEncrypter(block, nullBytes8)
+	mode.CryptBlocks(ciphertext, derivation)
+
+	return ciphertext, nil
+}
+
+func resizeKey24(key []byte) []byte {
+	data := make([]byte, 24)
+	copy(data, key[0:16])
+	copy(data[16:], key[0:8])
+
+	return data
+}

globalplatform/crypto/crypto_test.go

@@ -0,0 +1,26 @@
+package crypto
+
+import (
+	"testing"
+
+	"github.com/status-im/status-go/smartcard/hexutils"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestDeriveKey(t *testing.T) {
+	cardKey := hexutils.HexToBytes("404142434445464748494a4b4c4d4e4f")
+	seq := hexutils.HexToBytes("0065")
+
+	encKey, err := DeriveKey(cardKey, seq, DerivationPurposeEnc)
+	assert.NoError(t, err)
+
+	expectedEncKey := "85E72AAF47874218A202BF5EF891DD21"
+	assert.Equal(t, expectedEncKey, hexutils.BytesToHex(encKey))
+}
+
+func TestResizeKey24(t *testing.T) {
+	key := hexutils.HexToBytes("404142434445464748494a4b4c4d4e4f")
+	resized := resizeKey24(key)
+	expected := "404142434445464748494A4B4C4D4E4F4041424344454647"
+	assert.Equal(t, expected, hexutils.BytesToHex(resized))
+}