def gen_salt(msg):
"""! s1 SALT generation function
@param msg string
@return output of the salt generation
"""
key = b"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
ret = aes_cmac(key, msg.encode())
blog(f"SALT: {codecs.encode(ret, 'hex')}", "SALT")
return ret
def aes_ccm_encypt(k, n, m, a):
"""
@param k is 128-bit key
@param n is 104-bit nonce
@param m is the variable lenght data to be encrypted
and authenticated (plaintext)
@param a is the variable lenght data to be authenticated (additional data)
@return EncDST + EncTransportPDU
"""
c = AES.new(k, AES.MODE_CCM, nonce=n)
ret = c.encrypt(m)
blog(f"EncDST + EncTransportPDU: {codecs.encode(ret, 'hex')}", "SUCC")
return ret
def gen_k4(N):
"""! The k4 function
Used to generate an AID from an application key
@param N Appkey
@return Application keys AID
"""
salt = gen_salt("smk4")
T = aes_cmac(salt, N)
k4 = aes_cmac(T, "id6".encode() + b"\x01")
k4 = hex(((int.from_bytes(k4, byteorder="big")%2**6)))[2:].encode()
blog(f"k4: {k4}", "SUCC")
return k4
def gen_k3(N):
"""! The k3 function
Used to generate a public value of 64 bits derived from private key
@param N NetKey
@return NetworkID
"""
salt = gen_salt("smk3")
T = aes_cmac(salt, codecs.decode(N, 'hex'))
k3 = aes_cmac(T, "id64".encode() + b"\x01")
NetworkID = hex((int.from_bytes(k3, byteorder="big")%2**64))[2:].encode()
blog(f"NetworkID: {NetworkID}", "SUCC")
return NetworkID
def gen_k2(N, P=b'\x00'):
"""! The k2 function (master)
Used to convert the master security credentials
NetKey as N and generate the master security material
NID, EncryptionKey and PrivacyKey
@param N NetKey
@param P 0 or more bytes
@return List of EncryptionKey, PrivacyKey and NID
"""
salt = gen_salt("smk2")
T = aes_cmac(salt, codecs.decode(N, 'hex'))
T0 = b""
T1 = aes_cmac(T, T0 + P + b"\x01")
blog(f"T1: {codecs.encode(T1, 'hex')}", "PROC")
T2 = aes_cmac(T, T1 + P + b"\x02")
blog(f"T2: {codecs.encode(T2, 'hex')}", "PROC")
T3 = aes_cmac(T, T2 + P + b"\x03")
blog(f"T3: {codecs.encode(T3, 'hex')}", "PROC")
# 0x680953fa93e7caac9638f58820220a398e8b84eedec100067d670971dd2aa700cf
#nid = (hex(((int(codecs.encode(T1 + T2 + T3, 'hex'), 16))%2**263))).encode()
nid = (hex(((int(codecs.encode(T1 + T2 + T3, 'hex'), 16))%2**263))[2:4]).encode()
return [T2, T3, nid]
def defuscate(encDSTPDU, netMIC, ivindex, privacyKey, obfuscatedData):
"""
@param encDSTPDU EncDST + EncTransportPDU
@return List of CTL+TTL, SEQ, SRC
"""
privacyRandom = (encDSTPDU + netMIC)[:7]
blog(f"privacyRandom: {codecs.encode(privacyRandom, 'hex')}", "PROC")
privacyPlaintext = b"\x00\x00\x00\x00\x00" + ivindex + privacyRandom
blog(f"privacyPlaintext: {codecs.encode(privacyPlaintext, 'hex')}", "PROC")
pecb = e(privacyKey, privacyPlaintext)[:6]
blog(f"PECB: {codecs.encode(pecb, 'hex')}", "PROC")
ret = byteutils.bxor(obfuscatedData, pecb)
blog(f"(CTL || TTL || SEQ || SRC): {codecs.encode(ret, 'hex')}", 'SUCC')
return [ret[0:1], ret[1:4], ret[4:]]