diff --git a/sept/sept-secondary/KEYS_template.py b/sept/sept-secondary/KEYS_template.py
index 0b3a4ad9a..38cdcb0c4 100644
--- a/sept/sept-secondary/KEYS_template.py
+++ b/sept/sept-secondary/KEYS_template.py
@@ -1,7 +1,7 @@
-HOVI_ENC_KEY_PRD = '00000000000000000000000000000000'.decode('hex')
-HOVI_ENC_KEY_DEV = '00000000000000000000000000000000'.decode('hex')
-HOVI_SIG_KEY_PRD = '00000000000000000000000000000000'.decode('hex')
-HOVI_SIG_KEY_DEV = '00000000000000000000000000000000'.decode('hex')
-HOVI_KEK_KEY_PRD = '00000000000000000000000000000000'.decode('hex')
-HOVI_KEK_KEY_DEV = '00000000000000000000000000000000'.decode('hex')
-IV               = '00000000000000000000000000000000'.decode('hex')
+HOVI_ENC_KEY_PRD = bytearray.fromhex('00000000000000000000000000000000')
+HOVI_ENC_KEY_DEV = bytearray.fromhex('00000000000000000000000000000000')
+HOVI_SIG_KEY_PRD = bytearray.fromhex('00000000000000000000000000000000')
+HOVI_SIG_KEY_DEV = bytearray.fromhex('00000000000000000000000000000000')
+HOVI_KEK_KEY_PRD = bytearray.fromhex('00000000000000000000000000000000')
+HOVI_KEK_KEY_DEV = bytearray.fromhex('00000000000000000000000000000000')
+IV               = bytearray.fromhex('00000000000000000000000000000000')
diff --git a/sept/sept-secondary/sept_sign.py b/sept/sept-secondary/sept_sign.py
index 17d515433..a4dd83a87 100644
--- a/sept/sept-secondary/sept_sign.py
+++ b/sept/sept-secondary/sept_sign.py
@@ -9,48 +9,57 @@ except ImportError:
     import KEYS_template as KEYS
     print('Warning: output will not work on 7.0.0+!')
 
+
 def shift_left_xor_rb(s):
-    N = int(s.encode('hex'), 16)
+    if hasattr(int, "from_bytes"):
+      N = int.from_bytes(s, byteorder="big")
+    else:
+      N = int(s.encode('hex'), 16)
+
     if N & (1 << 127):
         N = ((N << 1) ^ 0x87) & 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
     else:
         N = ((N << 1) ^ 0x00) & 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
-    return ('%032x' % N).decode('hex')
+    return bytearray.fromhex('%032x' % N)
+
 
 def sxor(x, y):
-    return ''.join(chr(ord(a) ^ ord(b)) for a,b in zip(x, y))
-    
+    return bytearray(a^b for a,b in zip(x, y))
+
+
 def get_last_block_for_desired_mac(key, data, desired_mac):
     assert len(desired_mac) == 0x10
-    k1 = shift_left_xor_rb(AES.new(key, AES.MODE_ECB).encrypt('\x00'*0x10))
+    k1 = shift_left_xor_rb(AES.new(key, AES.MODE_ECB).encrypt(bytearray(0x10)))
     if len(data) & 0xF:
         k1 = shift_left_xor_rb(k1)
-        data += '\x80'
-        data += '\x00' * ((0x10 - (len(data) & 0xF)) & 0xF)
+        data += b'\x80'
+        data += bytearray((0x10 - (len(data) & 0xF)) & 0xF)
     num_blocks = (len(data) + 0xF) >> 4
-    last_block = sxor(AES.new(key, AES.MODE_ECB).decrypt(desired_mac), k1)
+    last_block = sxor(bytearray(AES.new(key, AES.MODE_ECB).decrypt(desired_mac)), bytearray(k1))
     if len(data) > 0x0:
-        last_block = sxor(last_block, AES.new(key, AES.MODE_CBC, '\x00'*0x10).encrypt(data)[-0x10:])
+        last_block = sxor(last_block, bytearray(AES.new(key, AES.MODE_CBC, bytearray(0x10)).encrypt(data)[-0x10:]))
     return last_block
 
+
 def sign_encrypt_code(code, sig_key, enc_key, iv, desired_mac):
     # Pad with 0x20 of zeroes.
-    code += '\x00' * 0x20
+    code += bytearray(0x20)
     code_len = len(code)
     code_len += 0xFFF
     code_len &= ~0xFFF
-    code += '\x00' * (code_len - len(code))
-    
+    code += bytearray(code_len - len(code))
+
     # Add empty trustzone, warmboot segments.
-    code += '\x00'* (0x1FE0 - 0x10)
-    pk11_hdr = 'PK11' + pk('<IIIIIII', 0x1000, 0, 0, code_len - 0x20, 0, 0x1000, 0)
+    code += bytearray(0x1FE0 - 0x10)
+    pk11_hdr = b'PK11' + pk('<IIIIIII', 0x1000, 0, 0, code_len - 0x20, 0, 0x1000, 0)
     pk11 = pk11_hdr + code
     enc_pk11 = AES.new(enc_key, AES.MODE_CBC, iv).encrypt(pk11)
     enc_pk11 = pk('<IIII', len(pk11) + 0x10, 0, 0, 0) + iv + enc_pk11
     enc_pk11 += get_last_block_for_desired_mac(sig_key, enc_pk11, desired_mac)
     enc_pk11 += CMAC.new(sig_key, enc_pk11, AES).digest()
     return enc_pk11
-    
+
+
 def main(argc, argv):
     if argc != 3:
         print('Usage: %s input output' % argv[0])
@@ -58,11 +67,12 @@ def main(argc, argv):
     with open(argv[1], 'rb') as f:
         code = f.read()
     if len(code) & 0xF:
-        code += '\x00'*(0x10 - (len(code) & 0xF))
+        code += bytearray(0x10 - (len(code) & 0xF))
     # TODO: Support dev unit crypto
     with open(argv[2], 'wb') as f:
-        f.write(sign_encrypt_code(code, KEYS.HOVI_SIG_KEY_PRD, KEYS.HOVI_ENC_KEY_PRD, KEYS.IV, 'THANKS_NVIDIA_<3'))
+        f.write(sign_encrypt_code(code, KEYS.HOVI_SIG_KEY_PRD, KEYS.HOVI_ENC_KEY_PRD, KEYS.IV, b'THANKS_NVIDIA_<3'))
     return 0
-        
+
+
 if __name__ == '__main__':
     sys.exit(main(len(sys.argv), sys.argv))