mirror of
https://github.com/bluekitchen/btstack.git
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74 lines
2.0 KiB
Python
74 lines
2.0 KiB
Python
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#!/usr/bin/env python3
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# BlueKitchen GmbH (c) 2019
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# pip3 install pycryptodomex
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# implementation of the Bluetooth SIG Mesh crypto functions using pycryptodomex
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from Cryptodome.Cipher import AES
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from Cryptodome.Hash import CMAC
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def aes_cmac(k, n):
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cobj = CMAC.new(k, ciphermod=AES)
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cobj.update(n)
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return cobj.digest()
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def aes_ccm_encrypt(key, nonce, message, additional_data, mac_len):
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cipher = AES.new(key, AES.MODE_CCM, nonce=nonce, mac_len=mac_len)
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cipher.update(additional_data)
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ciphertext, tag = cipher.encrypt_and_digest(message)
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return ciphertext, tag
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def aes_ccm_decrypt(key, nonce, message, additional_data, mac_len, mac_tag):
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cipher = AES.new(key, AES.MODE_CCM, nonce=nonce, mac_len=mac_len)
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cipher.update(additional_data)
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try:
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ciphertext = cipher.decrypt_and_verify(message, mac_tag)
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return ciphertext
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except ValueError:
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return None
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def s1(m):
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# s1(M) = AES-CMACZERO (M)
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zero_key = bytes(16)
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return aes_cmac(zero_key, m)
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def k1(n, salt, p):
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# T = AES-CMACSALT (N)
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t = aes_cmac(salt, n)
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# k1(N, SALT, P) = AES-CMACT (P)
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return aes_cmac(t, p)
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def k2(n, p):
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# SALT = s1(“smk2”)
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salt = s1(b'smk2')
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# T = AES-CMACSALT (N)
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t = aes_cmac(salt, n)
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# T0 = empty string (zero length)
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t0 = b''
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# T1 = AES-CMACT (T0 || P || 0x01)
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t1 = aes_cmac(t, t0 + p + b'\x01')
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# T2 = AES-CMACT (T1 || P || 0x02)
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t2 = aes_cmac(t, t1 + p + b'\x02')
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# T3 = AES-CMACT (T2 || P || 0x03)
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t3 = aes_cmac(t, t2 + p + b'\x03')
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nid = t1[15] & 0x7f
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encryption_key = t2
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privacy_key = t3
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return (nid, encryption_key, privacy_key)
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def k3(n):
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# SALT = s1(“smk3”)
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salt = s1(b'smk3')
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# T = AES-CMACSALT (N)
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t = aes_cmac(salt, n)
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return aes_cmac(t, b'id64' + b'\x01')[8:]
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def k4(n):
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# SALT = s1(“smk4”)
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salt = s1(b'smk4')
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# T = AES-CMACSALT (N)
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t = aes_cmac(salt, n)
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return aes_cmac(t, b'id6' + b'\x01')[15] & 0x3f
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