Motorola Wireless Broadband Platform Manuel utilisateur

Security and the Motorola

Canopy™ Wireless Broadband

Platform

(Advanced Security Techniques)

TABLE OF CONTENTS

Introduction......................................................................................................................... 1

Why Are Security Measures Necessary?............................................................................ 1

Clear Text Transmissions ............................................................................................... 1

Passive Monitoring ......................................................................................................... 2

End-to-End Security........................................................................................................ 2

Security Features of the Canopy System ............................................................................ 2

Canopy’s Proprietary Protocol........................................................................................ 3

Authentication................................................................................................................. 3

Key Management............................................................................................................ 4

Encryption....................................................................................................................... 5

Data Encryption Standard (DES)................................................................................ 5

Advanced Encryption Standard (AES) ....................................................................... 6

Summary............................................................................................................................. 8

List of Tables

Table 1. The Authentication Process ................................................................................. 4

Table 2. Canopy Key Management.................................................................................... 4

Table 3. Methods of Encryption and Their Associated Keys............................................. 7

iii

List of Acronyms

AES...................................................................Advanced Encryption Standard

AP.....................................................................Access Point

BAM .................................................................Bandwidth and Authentication Manager

BH.....................................................................Backhaul Module

CMM................................................................Cluster Management Module

DES ..................................................................Data Encryption Standard

DHCP ..............................................................Dynamic Host Configuration Protocol

FIPS........................................................Federal Information Processing Standards

IP ......................................................................Internet Protocol

LAN ..................................................................Local Area Network

NAT ..................................................................Network Address Translation

QoS...................................................................Quality of Service

SM.....................................................................Subscriber Module

SNMP...............................................................Simple Network Management Protocol

SQL...................................................................Structured Queary Language

TIA....................................................................Telecommunications Industry Association

NOTICE

The information in this publication is subject to change without notice. Motorola shall not be

liable for technical or editorial errors or omissions nor for any damages resulting from the use of

this material.

Each configuration tested or described may or may not be the only available solution. This test is

not a determination of product quality or correctness, nor does it ensure compliance with any

federal, state or local requirements. Motorola does not warrant products other than its own

strictly as stated in Motorola’s product warranties.

MOTOROLA and the Stylized M Logo are registered in the US Patent & Trademark Office.

Canopy is a trademark of Motorola, Inc. All other product or service names are the property of

their respective owners. © Motorola, Inc. 2003.

INTRODUCTION

Until just recently, it would have been unimaginable for medical institutions to exchange

high resolution digital imagery over wireless networks. Why, you may ask? Not only

were the early wireless systems incapable of transmitting detailed medical images over

their seemingly small pipes — originally designed to carry voice conversations — but

securing this sensitive data from vulnerabilities such eavesdropping, session hijacking,

data alteration and manipulation (among others) and ultimately protecting the privacy of

the patient seemed an insurmountable challenge.

Over the last 10 years, Motorola has been investigating the use of fixed wireless

broadband systems and has brought to the marketplace a product that is capable of not

only handling these incredibly large digital medical images with lightning fast speeds but

has integrated advanced security measures into the product that transparently, efficiently

and effectively safeguard the precious information that is transmitted over Motorola’s

Canopy™ wireless broadband system. Today, medical institutions have moved far

beyond simply imagining the use of wireless broadband systems to actually applying the

technology to collaborate and often times performing life saving diagnostics.

This paper Security and the Motorola Canopy Broadband Wireless Platform offers a

snapshot of some of the security issues being faced by the wireless broadband industry as

well as the safeguards that Motorola is employing in the Canopy platform to ensure the

security and integrity of this advanced system for our customers.

WHY ARE SECURITY MEASURES NECESSARY?

When the Internet was first introduced, there was little concern about security measures.

The specifications for the Internet Protocol (IP) did not take into account the fact that

operators may actually need to protect the data that they were transmitting. Obviously a

great deal has changed since that time. Seemingly harmless attacks have wreaked havoc

on computer networks with wireless adding a new dimension of vulnerability. The first

step in understanding how these attacks can be prevented is in analyzing the basic

weaknesses in a typical IP system.

CLEAR TEXT TRANSMISSIONS

When data is transmitted over an IP network, all information is relayed as clear text.

That is to say, the data is not scrambled or rearranged and is transmitted purely in its raw

form. This information includes both the data and authentication streams of information

and is referred to as transmitting in the clear. When transmitting clear text transmissions,

websites visited, downloaded information — everything — is open to the prying eyes of

anyone with a network analyzer.

PASSIVE MONITORING

As mentioned previously, it is relatively easy to monitor clear text transmissions over an

IP network. Unfortunately, most of the time invaders are not easily detected. This is

because monitoring of the traffic is performed using passive devices that do not transmit

any data of their own. Therefore, they can’t be easily detected. In addition, attackers do

not require physical access to any particular facility to conduct these passive monitoring

sessions.

END-TO-END SECURITY

While hackers don’t require physical access to monitor (hack) a network, they can be

easily connected by placing a probe or analyzer anywhere along the transmission path —

from system initialization to destination. Since vulnerabilities can exist anywhere along

the IP transmission path, complete system security can only be achieved by applying end-

to-end security measures. The security measures built into the Canopy system

architecture are designed to cover only the wireless portions of the network. These

include:

•Access Point (AP)

•Subscriber Module (SM)

•Backhaul (BH) Module

•Cluster Management Module (CMM)

•Bandwidth and Authentication Manager (BAM)

The Canopy system security does not include elements outside of the wireless transport,

such as:

•Client (Computer)

•Wireless Modems

•Local Area Networks

•Routers

•Printers

•Servers

•Various Network Peripheral Equipment

Protecting equipment outside of the Canopy system from security invasions can be

accomplished using software, devices and security techniques from various

manufacturers and should be included as part of an end-to-end system design.

SECURITY FEATURES WITHIN CANOPY SYSTEM

Privacy and integrity of data are key considerations for both broadband network

subscribers and operators. Security and authentication to prevent unwanted access to

critical data or services are necessary for the effective operation of any broadband

network. Applications such as medical, remote surveillance, safety, security and

homeland defense would not be possible without incorporating advanced security

features into the fixed wireless network. Gone are the days when it wasn’t necessary to

be concerned with security as a fundamental building block.

Today, the Canopy system incorporates a flexible security model that supports a wide

variety of system configurations ranging from a fully open system to an

authenticated/encrypted air link with dynamic session key assignment. The Canopy

system uses industry proven authentication and encryption technologies to ensure that the

service provider maintains control of the network. The system comes with Data

Encryption Standard (DES) to protect against eavesdropping and Advanced Encryption

Standard (AES) is available as an option for customers requiring the most secure network

available. The following paragraphs highlight each of these advanced features in further

detail.

CANOPY’S PROPRIETARY PROTOCOL

Canopy’s proprietary air interface provides a strong foundation against attacks by

invaders. First of all, because the Canopy system is based on a proprietary protocol, there

are no published specifications for the product by which sniffer radios could be built. In

addition, a sniffer would require the proprietary Canopy chip set that is not readily

available. Second, the MAC protocol for packet assembly, disassembly and

retransmission is not published. Third, data transmitted over the air is scrambled into 64-

byte data packages thus providing an additional obstacle to unauthorized decoding.

Finally, the directionality of the Canopy system transmissions impedes eavesdropping.

In other words, the proprietary air interface presents a major hurdle for unauthorized

parties. Of course, the Canopy system’s security is not based merely on secrecy of its air

interface.

AUTHENTICATION

Clearly it is inadvisable to transmit information that one assumes is secure using clear

text as it can be easily monitored. Unlike many fixed wireless broadband products, the

Canopy system does not use clear text transmissions but rather a proprietary protocol for

transmissions. When this protocol is combined with the Canopy Bandwidth and

Authentication Manager (BAM), an added level of security is achieved for the operator

and the network.

The BAM controls access to a Canopy system, and each AP module can be configured to

require secure SM authentication prior to providing network access. Each SM must be

authenticated by the BAM before entering the network. SMs are authenticated and keys

are managed individually. The authentication process also takes into account the

electronic serial number unique to each transceiver along with a 128-bit secret key that is

unique to each SM and is known only to the network operator. The eight step

authentication process is shown in Table 1.

Table 1. The Authentication Process

Step

Description of Task

When an SM attempts to enter the Canopy network

it sends a registration request to the AP.

The AP then sends an authentication request to the

BAM.

The BAM generates a 128 bit random number that is

sent to the SM as a challenge.

The SM calculates a response using either its factory

set key or the Authorization key it has been assigned

by the network operator.

This challenge response is sent to the BAM through

the AP.

The BAM compares the challenge response to what

it calculated using the same random number and the

Authentication key from the BAM SQL database.

If the results agree, the BAM sends the AP a

message authenticating the SM and sends the SM

and AP QoS information.

If the results do not agree or the SM is not in the

database the BAM sends the AP a message denying

authentication and the AP sends the SM a message

to lock itself out from that AP for 15 minutes before

retrying.

KEY MANAGEMENT

The Canopy system uses an ESN, two keys and a random number for authentication.

Table 2 details the functionality of each of these along with the random number.

Table 2. Canopy Key Management

Key/Number

Description

Electronic Serial Number

Each Canopy SM has a factory set ESN that

cannot be changed. The ESN is the identifier

which is being authenticated and is 48 bits in

length.

Authentication Key

(Authorization key or Skey)

This key is set by the network operator in the

BAM SQL database and by either the network

operator or by the subscriber in the SM. This

key can be seen in the BAM SQL database by

the network operator; it can’t be displayed in

the SM Configuration web page by

subscriber. It is 128 bits in length.

Key/Number

Description

Session Key

The session key is calculated separately by the

SM and the BAM, using the Authentication

Key, the ESN, and the random number. This

key is sent to the AP by the BAM – like the

other keys, it never goes over the air. The

network operator or the subscriber never sees

this key. This key is either 56 bits (DES) or

128 bits (AES) in length.

Random Number

A random number is generated by the BAM

and used during each attempt by an SM to

network operator never sees this number. This

is a 128 bit number.

Of the three numbers presented in Table 2, only the Authentication Key is settable by the

network operator and it must be set both in the BAM and in the SM. Further information

about Canopy’s authentication process is detailed in Bandwidth and Authentication

(BAM) User Guide.

ENCRYPTION

The Canopy system also has provisions for the industry-accepted DES with key

management via the Telecommunications Industry Association (TIA) standard BRAID

cryptosystem. In addition, the Canopy system provides for AES for customers who

require the most secure networks available. These encryption techniques are transparent

to network firewalls, Dynamic Host Configuration Protocol (DHCP) servers and Network

Address Translation (NAT) devices.

Data Encryption Standard (DES)

DES is an encryption standard that uses an encryption technique developed in the mid

1970s by IBM and then adopted by the Federal government as a federal standard in 1977

for protecting sensitive, but not classified data. DES was designed so that even if

someone knows some of the plain text data and the corresponding ciphertext, there is no

way to determine the key without trying all possible keys. The strength of DES

encryption based security rests on the size of the key and the proper protection of the

key.1The following paragraphs discuss details of DES from the document entitled,

Federal Information Processing Standards (FIPS) PUB 46-3 Data Encryption Standard

(DES):

The Data Encryption Standard (DES) specifies two Federal Information

Processing Standards (FIPS) approved cryptographic algorithms as required by

FIPS 140-1. Encrypting data converts it to an unintelligible form called cipher.

1Security Complete, Adapted from Active Defense, by Chris Brenton with Cameron Hunt.

Decrypting cipher converts the data back to its original form called plain text.

The algorithms for DES described in the DES standard specifies both enciphering

and deciphering operations which are based on a binary number called a key.

A DES key consists of 64 binary digits ("0"s or "1"s) of which 56 bits are

randomly generated and used directly by the algorithm. The other 8 bits, which

are not used by the algorithm, may be used for error detection. The 8 error

detecting bits are set to make the parity of each 8-bit byte of the key odd, i.e.,

there is an odd number of "1"s in each 8-bit byte2. Authorized users of encrypted

computer data must have the key that was used to encipher the data in order to

decrypt it. The encryption algorithms specified in the standard are commonly

known among those using the standard. The cryptographic security of the data

depends on the security provided for the key used to encipher and decipher the

data.

Data can be recovered from cipher only by using exactly the same key used to

encipher it. Unauthorized recipients of the cipher who know the algorithm but do

not have the correct key cannot derive the original data algorithmically.

However, it may be feasible to determine the key by a brute force “exhaustion

attack.” Also, anyone who does have the key and the algorithm can easily

decipher the cipher and obtain the original data. A standard algorithm based on a

secure key thus provides a basis for exchanging encrypted computer data by

issuing the key used to encipher it to those authorized to have the data.

Data that is considered sensitive by the responsible authority, data that has a high

value, or data that represents a high value should be cryptographically protected if

it is vulnerable to unauthorized disclosure or undetected modification during

transmission or while in storage.”

Advanced Encryption Standard (AES)

AES Standard is the follow-up to DES and is the result of an exhaustive evaluation by the

National Institute of Standards and Technology that began in 1997 with a notice

soliciting an unclassified, publicly disclosed encryption algorithm that would be available

royalty-free worldwide. Following the submission of 15 candidate algorithms and three

publicly held conferences to discuss and analyze the candidates, the field was narrowed

to five candidates. NIST continued to study all available information and analyses about

the candidate algorithms, and selected one of the algorithms, the Rijndael algorithm, to

propose for the AES. The Rijndael algorithm is a variable length block cipher, but its

implementation in AES is 128 bits. In decimal terms, this means that there are

approximately:

3.4 x 1038 possible 128-bit keys;

2Sometimes keys are generated in an encrypted form. A random 64-bit number is generated and defined to

be the cipher formed by the encryption of a key using a key encrypting key. In this case the parity bits of

the encrypted key cannot be set until after the key is decrypted.

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