Adding support for Ciphering algorithm in 5G SA for NAS data

Overview

Current Magma 5G supports all the mandatory integrity algorithms like IA1 and IA2 but on the Encryption front it supports only the mandatory EA0 which is Null-Encryption. TS 33.501 covers mandatory and higly desirable ciphering algorithms {EA0, EA1, EA2} to be supported. This proposal intendes to add support for ciphering algorithms {EEA1 and EEA2}.

Solution

The way it will be realized is to extend the current capabilities of magma which will be exchanged and agreed upon during the Security Mode Procedures. Based on the configuration flow the uplink Nas data will be decrypted and downlink Nas data will be encrypted. Decryption might also be followed by integrity protection procedure based on the configuration.
Any packet after Security Mode Completion will be accepted based on agreed capabilities.

Call Flow

Key Generation

Elements impacted mainly will be MME module

128-NEA1 Algorithm

128-NEA1 :Its based on the Snow 3G stream cipher. Snow 3G is a 32-bit word-oriented stream cipher supporting 128-bit keys, which was also part of the 3G standard. The 3GPP standard supports the encryption (128-NEA1) or authentication (128-NIA1) of blocks of data from 1 to 20’000 bits

• Encryption

EEA1(key=16b'\xc1', count=0x9955ab, bearer=0x16, dir=1, data_in=50b'MonPantalonS'EstDecousu', bitlen=1149)
b'\xc4\xce\xf2\x98\xf0\x92G\x14T\xdc\x9e\xa6LN\x89\xc3\xb9\xff\xce\xb7\x02\xeei=\xe1ZQ\xe7\xf5\xff\x13\xb6\x94\x8f\x1a<w\xc0'W\xe8\xd0\xcc-\x8c\t\x10\xa4\x0eT!&\x11\\xd1v\x96\xb99l\x0eX\xffaR\xb2\x1d\xe0\x8a\x11\x06\xb9;b\xda\xeb@\xe0#o\xba\x17\x14\xa2j\x8d\xcf\x9a\x84ahTi["u'2\xb5t\x90\x16}\x80\xeb\x9f\xe52\xb3\xdb7\xa1H9\xc0W\x8cA\xd3\xcf0\x04\r\xecv\xea5\xe8\xaar\xf3$\xf9}\x12\xab,W\L\x0f\x9e\x0f8'

• Decryption

EEA1(key=16*b'\xc1', count=0x9955ab, bearer=0x16, dir=1, data_in=_, bitlen=1149)
b"MonPantalonS'EstDecousuMonPantalonS'EstDecousuMonPantalonS'EstDecousuMonPantalonS'EstDecousuMonPantalonS'EstDecousuMonPantalonS'EstDecousuMonPah"

128-NEA2 Algorithm

128-NEA2 :Its based on the AES block cipher. AES is probably the block cipher that has been the most analyzed in the history of cryptography.

• Encryption

EEA2(key=16b'\xc1', count=0x9955ab, bearer=0x16, dir=1, data_in=50b'MonPantalonS'EstDecousu', bitlen=1149)
b'-y\xf1\xee\xb7\xe4\x0c\xf2\xdfz`\xb04"\x8c\xda\xc8B!n\x863V"\xaei\x91\x1b\xc5\xfc\x1dx\xb9l\xe8\x99q\q\x88\x91\xc8f\r\x05\xdf\x94S\x97\xc0\x96\xb75\x00@\xfea\x840\xdb\xa3\x88\x15\x03\x9e\xa4\x98\xa5\x82\xb649\xcez5\xd3\x01\x93\x97\x1dpx\xacW\xe9\xb9.mE3\xb9\xc1\xb8\xbd\x06\x8bI\x7f\xf6\x90A\xd3P\xc9\xbe\xbaE\xa8\xbe\xc2GDQ\x17l\xf7\xac\x0f\x96E\xd0}\x8dw\x80k\x8f\n\xeeW\x94\xfa\xa9/\xc2\x02so\xf4yV\xcad\xf0'

• Decryption

EEA2(key=16*b'\xc1', count=0x9955ab, bearer=0x16, dir=1, data_in=_, bitlen=1149)
b"MonPantalonS'EstDecousuMonPantalonS'EstDecousuMonPantalonS'EstDecousuMonPantalonS'EstDecousuMonPantalonS'EstDecousuMonPantalonS'EstDecousuMonPah"