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INTERNET-DRAFT                                            Naresh Kumar
Intended Status: Standards Track                          NIT Delhi
Expires: February 11, 2019                                K.Verma
                                                          NIT Delhi

                                                       August 11, 2018

                             Security for 5G
                   draft-naresh-kitten-security-for-5g-00.txt




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   Abstract

   This document proposes a new method which provides the capability to
   resolve issue of attack over Mobile Communication System.  This
   document assumes that the reader is familiar with some concepts and
   details regarding Authentication and Encryption in generations of
   Mobile Telephony.






Table of Contents

   1  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2  Vulnerability Desription . . . . . . . . . . . . . . . . . . . . 3
   3  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   4  General Scenario       . . . . . . . . . . . . . . . . . . . . . 3
   5  Solutions of these issues . . . . . . . . . . . . . . . . . . .  4
   6  IANA Considerations . . . . . . . . . . . . . . . . . . . . . .  5
   7  Security Considerations. . . . . . . . . . . . . . . . . . . . . 5
   8  Conclusions  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
   9  References . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
   10 Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . .  7
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .  7
















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1  Introduction
In Mobile Communication,IMSI catching is the major issue today.
In order to encrypt or decrypt data between Mobile Station and Base
Station,various algorithms are implemented by generating keys required
to provide confidentiality and integrity.

2 Vulnerability
Initially whenever UE attaches for the first time[3], it sends the IMSI
to MME in clear text which is sent from MME to eNodeBs and from eNodeBs
to UEs.An attacker can request without awareness of the user by using
various social engineering tools and then trace messages between eNodeB
and UE to decode them and fetch the IMSI . There is also another Fault
that occurs whenever re-synchronisation occurs at the time of handover
because at that time also, IMSI is sent in plaintext that can easily
be sniffed by attacker.

                   +------------+ +----------------------+   +--------+
+------+           |Fake Station| | Base Station(Actual) |   |Network |
|      |           +------------+ +----------------------+   +--------+
|Mobile|   IMSI    |    IMSI      |     IMSI                 |
|Statio| --------> |------------> |------------->            |
|n     | AUTN,RAND |              |                          |
|      |<--------- |              |   AUTN,RAND              |
|      |    RES    |    RES       |<--------------
+------+------->   |------------> |


3  Terminology
Refer 9.2[2] for better visualisation
3.1 IMSI: An international mobile subscriber identity is a unique number
usually fifteen digits, associated with Global System for Mobile
Communications i.e GSM and Universal Mobile Telecommunications System
UMTS network mobile phone users. The IMSI is a unique number identifying
a subscriber
3.2 AUTN: Authentication Token
3.3 MME : Mobility Management Entity,Handling all management like
handover etc
3.4 HSS : Home Subscriber Server-User USIM Company
3.5 AAA :Authentication,Authorisation,accounting
3.6 C1,C2 : Ciphertexts

4 General Scenario
Normally in all advanced generations,excluding 1G/2G of Mobile
Communications "AUTHENTICATION AND KEY AGREEMENT(AKA)PROTOCOL" steps
are applied for Mutual Authentication:
 1. Mutual authentication between the network and UE.
 2. Deriving keys for confidentiality and integrity protection.
 3. confidentiality, integrity among various Entities like core network
 4. Temporary identity like GUTI are used to hide IMSI




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Now there are various Algorithms like in 9.1[1],[2] that can be applied
in SIM and MME to generate the RES(Response),AUTN that includes sequence
number etc in order to get the keys that help to verify each other
identity and thus are required to encrypt the data for secure
communication.This same procedure can be applied to 5G system.


5 Solutions of these issues

Now there are two methods to achieve protection against the attacker
regarding IMSI catching:

5.1 We can use Public key Cryptosystem in order to encrypt IMSI to
reduce problem of IMSI Catching and that particular algorithm which has
been used to encrypt is confidential only to the UE and gNodeB Mobile
station for 5G

5.2 Every time a mobile SIM try to connect Base Station, it should use a
pseudonym IMSI that will be updated in both the station(Home Server as
well as Mobile SIM) and there will be checking for all updations that
will lead to provide Both Authenticity and Confidentiality. So each time
user will get the new updated IMSI and will be identified by this
Identity only.
Now coming to the main Method(Public key Cryptosystem)we have
implemented various algorithms based on following scheme keeping the
message constant:

+--------+        +----------+      +------+
|        |        | Message  |----> |  MAC |
| Sender |        +----------+      +------+
|  side  |            |                |
|        |            | key1(Algo)     |
|        |            v                v
+--------+           C1 ----->   +----------+  key2(Algo)
                                 |  C1||MAC |---------->C2
                                 +----------+           |
             +------------------------------------------+
             | (Channel)
             |
+--------+   +----+---+ key2(Algo) +---------+   +--------+
|        |   |    C2  |----------->| C1||MAC |-->|  MAC   |----|
|Reciever|   +--------+            +---------+   +--------+    |
|  side  |                            |                        |
|        |                            |               +------------+
|        |                            v               | MAC==XMAC??|
+--------+                       +-------+            +------------+
                                 |  C1   |-----+           |
                                 +-------+     |        +--------+
                                    |          +------> |  XMAC  |
                                key1(Algo)              +--------+
                                    v
                                +--------+
                                |Message |
                                +--------+

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According to the diagram, Message confidentiality and Authenticity is
achieved using MAC(Message Authentication code)see[RFC 6476]. We have
implemented three algorithms(Blowfish[],AES[RFC 3962])

Implemented Algorithms and their results:

+------------+-----------------+------------+--------------+
| PARAMETERS | FERNET(AES-128) | AES        | BLOWFISH     |
|------------+-----------------+------------+--------------+
| KEY LENGTH |     128         |  128,192,  |Variable key  |
|  (Bits)    |                 |    256     |length(32,448)|
|------------+-----------------+------------+--------------+
|  ROUNDS    |    10,12,14     |  10,12,14  |    16        |
|------------+-----------------+------------+--------------+
| LEVEL OF   |     Medium      |  Highly    |  Excellent   |
| SECURITY   |    Security     |  Secure    |  Security    |
|------------+-----------------+------------+--------------+
| ENCRYPTION |    Moderate     |  Faster    | Very fast    |
|  SPEED     |                 |            |              |
|------------+-----------------+------------+--------------+
|  TIME(s)   |    0.004000     |  0.004003  |  0.004008    |
|------------+-----------------+------------+--------------+



6  IANA Considerations

   Nil

7 Security Considerations

For solutions we have already described in section 5 We can use
different algorithms at different positions like at the time
of generation of cipher C1 or C2 etc. There is no restriction over its
sequence. We are considerig that the keys have already been exchanged or
already fixed in the center server's database corresponding to the
particular SIM. for more details on architecture you can see 9.2[1]


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8 Conclusions

This document is mainly focussed over the major vulnerability of
Mobile Generations in the form of IMSI transmission in plaintext. We
can not only encrypt this confidential information but other details can
also be secured. This can be effective in upcoming 5th Generation also.

9 References

9.1  Normative References

[RFC 6476] Errata Exist,P. Gutmann "Using Message Authentication Code
(MAC) Encryption in the Cryptographic Message Syntax (CMS)"

[RFC 3962] K.Raeburn "Advanced Encryption Standard (AES) Encryption for
Kerberos 5"

9.2  Informative References

[1] https://portal.3gpp.org/desktopmodules/Specifications/Specification
    Details.aspx?specificationId=3144.
[2] E. Dahlman, S. Parkvall, J. Skold, 4G: LTE/LTE-advanced for mobile
    broadband, Academic, 2013.
[3] https://ieeexplore.ieee.org/document/7397256/






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10 Acknowledgements

   This document is prepared for M. Tech 2nd year Major Project in
   National Institute of Technology, Delhi.


Authors' Addresses


   Naresh Kumar
   M. Tech Student
   Department of Computer Science & Engineering
   National Institute of Technology, Delhi
   Narela, Delhi-110040,INDIA

   Phone: +91- 8839338318
   EMail: 172211007@nitdelhi.ac.in

   Karan Verma
   Assistant Professor
   Department of Computer Science & Engineering
   National Institute of Technology, Delhi
   Narela, Delhi-110040,INDIA

   Phone: +91-7568169258
   EMail:  karan.verma.phd@gmail.com











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