1 files changed, 45 insertions, 22 deletions

diff --git a/freestyle_hid/_freestyle_encryption.py b/freestyle_hid/_freestyle_encryption.py
index 0461cb8..a0268eb 100644
--- a/freestyle_hid/_freestyle_encryption.py
+++ b/freestyle_hid/_freestyle_encryption.py
@@ -6,7 +6,7 @@
 class SpeckEncrypt:
     def __init__(self, key):
         # Perform key expansion and store the round keys
-        self.key = key & ((2 ** 128) - 1)
+        self.key = key & ((2**128) - 1)
         self.key_schedule = [self.key & 0xFFFFFFFF]
         key_buf = [(self.key >> (x * 32)) & 0xFFFFFFFF for x in range(1, 4)]
         for x in range(26):
@@ -58,13 +58,19 @@ class SpeckEncrypt:
     def encrypt(self, iv, plain):
         plain = bytearray(plain)
         input_length = len(plain)
-        plain.extend(bytes(b'\x00' * (8 - (input_length % 8))))
-        iv = int.from_bytes(iv.to_bytes(8, byteorder='big'), byteorder='little', signed=False)
+        plain.extend(bytes(b"\x00" * (8 - (input_length % 8))))
+        iv = int.from_bytes(
+            iv.to_bytes(8, byteorder="big"), byteorder="little", signed=False
+        )
         output = bytearray()
         for i in range(len(plain) // 8):
             k = self.encrypt_block(iv)
-            res = k ^ int.from_bytes(plain[i*8:i*8+8], byteorder='little', signed=False)
-            output.extend(int.to_bytes(res, 8, byteorder='little', signed=False))
+            slice_start = i * 8
+            slice_end = slice_start + 8
+            res = k ^ int.from_bytes(
+                plain[slice_start:slice_end], byteorder="little", signed=False
+            )
+            output.extend(int.to_bytes(res, 8, byteorder="little", signed=False))
             iv += 1
         encrypted = output[:input_length]
         return bytes(encrypted)
@@ -72,24 +78,30 @@ class SpeckEncrypt:
     def decrypt(self, iv, encrypted):
         return self.encrypt(iv, encrypted)
 
-class SpeckCMAC:
 
+class SpeckCMAC:
     def __init__(self, key):
         self.cipher = SpeckEncrypt(key)
 
         k0 = self.cipher.encrypt_block(0)
-        k0 = int.from_bytes(k0.to_bytes(8, byteorder='big'), byteorder='little', signed=False)
+        k0 = int.from_bytes(
+            k0.to_bytes(8, byteorder="big"), byteorder="little", signed=False
+        )
 
-        k1 = (k0 << 1) & 0XFFFFFFFFFFFFFFFF
-        if (k0 >> 63 != 0):
+        k1 = (k0 << 1) & 0xFFFFFFFFFFFFFFFF
+        if k0 >> 63 != 0:
             k1 ^= 0x1B
 
-        k2 = (k1 << 1) & 0XFFFFFFFFFFFFFFFF
-        if (k1 >> 63 != 0):
+        k2 = (k1 << 1) & 0xFFFFFFFFFFFFFFFF
+        if k1 >> 63 != 0:
             k2 ^= 0x1B
 
-        k1 = int.from_bytes(k1.to_bytes(8, byteorder='big'), byteorder='little', signed=False)
-        k2 = int.from_bytes(k2.to_bytes(8, byteorder='big'), byteorder='little', signed=False)
+        k1 = int.from_bytes(
+            k1.to_bytes(8, byteorder="big"), byteorder="little", signed=False
+        )
+        k2 = int.from_bytes(
+            k2.to_bytes(8, byteorder="big"), byteorder="little", signed=False
+        )
         self.k1 = k1
         self.k2 = k2
 
@@ -98,22 +110,33 @@ class SpeckCMAC:
         i = 0
         data_len = len(data)
 
-        while (i < data_len):
+        while i < data_len:
             data_left = data_len - i
-            if (data_left == 8):
-                block = int.from_bytes(data[i:i+8], 'little') ^ self.k1
-            elif (data_left < 8):
-                block = int.from_bytes(data[i:i+data_left] + b'\x80' + b'\x00'*(7-data_left), 'little') ^ self.k2
+            slice_start = i
+            slice_end = slice_start + 8
+            if data_left == 8:
+                block = int.from_bytes(data[slice_start:slice_end], "little") ^ self.k1
+            elif data_left < 8:
+                slice_end = i + data_left
+                block = (
+                    int.from_bytes(
+                        data[slice_start:slice_end]
+                        + b"\x80"
+                        + b"\x00" * (7 - data_left),
+                        "little",
+                    )
+                    ^ self.k2
+                )
             else:
-                block = int.from_bytes(data[i:i+8], 'little')
+                block = int.from_bytes(data[slice_start:slice_end], "little")
             c = self.cipher.encrypt_block(c ^ block)
             i += 8
 
         return c
 
     def derive(self, label, context):
-        data = label + b'\x00' + context + b'\x80\x00'
-        d1 = self.sign(b'\x01' + data)
-        d2 = self.sign(b'\x02' + data) << 64
+        data = label + b"\x00" + context + b"\x80\x00"
+        d1 = self.sign(b"\x01" + data)
+        d2 = self.sign(b"\x02" + data) << 64
 
         return d1 | d2