From f285fcba0a707e943ef95eb2334de7b79b1c07dc Mon Sep 17 00:00:00 2001
From: MPM1107 <majpimo@gmail.com>
Date: Fri, 23 Jun 2023 18:36:56 +0200
Subject: initial encrypted protocol support

---
 freestyle_hid/_freestyle_encryption.py | 115 +++++++++++++++++++++++++++++++++
 1 file changed, 115 insertions(+)
 create mode 100644 freestyle_hid/_freestyle_encryption.py

(limited to 'freestyle_hid/_freestyle_encryption.py')

diff --git a/freestyle_hid/_freestyle_encryption.py b/freestyle_hid/_freestyle_encryption.py
new file mode 100644
index 0000000..eb04303
--- /dev/null
+++ b/freestyle_hid/_freestyle_encryption.py
@@ -0,0 +1,115 @@
+class SpeckEncrypt():
+
+    def __init__(self, key):
+        # Perform key expansion and store the round keys
+        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):
+            k = self.encryption_round(key_buf[x], self.key_schedule[x], x)
+            key_buf.append(k[0])
+            self.key_schedule.append(k[1])
+
+    def encryption_round(self, x, y, k):
+        # Perform one encryption round of the speck cipher
+        x_shift = ((x << 24) + (x >> 8)) & 0xFFFFFFFF
+        x_enc = k ^ ((x_shift + y) & 0xFFFFFFFF)
+        y_shift = ((y >> 29) + (y << 3)) & 0xFFFFFFFF
+        y_enc = x_enc ^ y_shift
+
+        return x_enc, y_enc
+
+    def decryption_round(self, x, y, k):
+        # Perform one decryption round of the speck cipher
+        new_y = (((x ^ y) << 29) + ((x ^ y) >> 3)) & 0xFFFFFFFF
+        msub = (((x ^ k) - new_y) + 0x100000000) % 0x100000000
+        new_x = ((msub >> 24) + (msub << 8)) & 0xFFFFFFFF
+
+        return new_x, new_y
+
+    def encrypt_block(self, plain):
+        # Encrypt one 64 bit block
+        x = (plain >> 32) & 0xFFFFFFFF
+        y = plain & 0xFFFFFFFF
+
+        for k in self.key_schedule:
+            x, y = self.encryption_round(x, y, k)
+
+        encrypted = (x << 32) + y
+
+        return encrypted
+
+    def decrypt_block(self, encrypted):
+        # Decrypt one 64 bit block
+        x = (encrypted >> 32) & 0xFFFFFFFF
+        y = encrypted & 0xFFFFFFFF
+
+        for k in reversed(self.key_schedule):
+            x, y = self.decryption_round(x, y, k)
+
+        plain = (x << 32) + y
+
+        return plain
+
+    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)
+        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))
+            iv += 1
+        encrypted = output[:input_length]
+        return bytes(encrypted)
+
+    def decrypt(self, iv, encrypted):
+        return self.encrypt(iv, encrypted)
+
+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)
+
+        k1 = (k0 << 1) & 0XFFFFFFFFFFFFFFFF
+        if (k0 >> 63 != 0):
+            k1 ^= 0x1B
+
+        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)
+        self.k1 = k1
+        self.k2 = k2
+
+    def sign(self, data):
+        c = 0
+        i = 0
+        data_len = len(data)
+
+        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
+            else:
+                block = int.from_bytes(data[i:i+8], '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
+
+        return d1 | d2
-- 
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