1 / 30

Basic security

Basic security. Module contents. Spread Spectrum Network Name / Closed System Authentication WEP Encryption MAC address based Access Control IEEE 802.1x Security. Complete Bandwidth Allocated. Spread Spectrum. Direct Sequence SS Technique Simultaneous use of multiple frequencies

mele
Download Presentation

Basic security

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Basic security

  2. Module contents • Spread Spectrum • Network Name / Closed System • Authentication • WEP Encryption • MAC address based Access Control • IEEE 802.1x Security

  3. Complete Bandwidth Allocated Spread Spectrum • Direct Sequence SS Technique • Simultaneous use of multiple frequencies • Signal spread many times • Radio Signals cannot be traced • 35 mW is spread over 22 MHz • No single carrier frequency to scan • Regular band scanning devices will not be able to detect the information that is transmitted • Data can only be picked up by similar device • Spread spectrum is not providing security on its own, but makes it less easy simple sniffers to capture data from the air Information is chopped into eleven parts and transmitted

  4. Network Name / Closed SystemNetwork Name • Uses “Network Name” as part of the protection scheme • Provides hurdle to for un-authorized users to enter the network • Requires the user to know the “network name” in order to get associated • Recommended to use a non-trivial character string as the value of the “network name” Note: The prime usage for the “Network Name” is to separate networks from each other that share the same media • Should be used in combination with the “closed system option” to be effective as part of the protection scheme

  5. Network Name / Closed SystemClosed System Option • Access Point accepts only Stations with correct “Network Name” • “ANY” (broadcast “Network Name”) not accepted • No response to Probe Request without correct “Network Name” • (Re-)Association Request without correct “Network Name” responded to with failure status code • “Network name” not included in Beacon to avoid “passive scan” • Not IEEE 802.11 compliant

  6. AuthenticationDefined by IEEE 802.11 standard Open System Authentication • Stations authenticate at each Access-Point once before their first association to the Access-Point • A roaming station may need to re-authenticate at the Access-Point that it is roaming to, even though it has been authenticated by the Access Point it roams away from • IEEE 802.11 defines: • Open System Authentication • Shared Key Authentication (based on WEP) • ORiNOCO Clients do not activate Shared Key Authentication, but the APs will react as defined when non-ORiNOCO clients activate it. Authentication request (Open System Authentication) Authentication response Shared Key System Authentication

  7. EncryptionWired Equivalent Privacy • “64 WEP” standard available in Turbo 11 Mb Silver cards • 40-bit secret key + 24-bits Initialization Vector (IV) • IEEE 802.11 standard • “128RC4” available in Turbo 11 Mb Gold cards • 104-bit secret key + 24-bits Initialization Vector (IV) • Not IEEE 802.11 compliant • Single Key per Network • multiple keys for Receive to allow key change-over

  8. Secret Key WEP IV IV IV PRNG Plaintext WEP TX + Secret Key PRNG Ciphertext Ciphertext + Plaintext Integrity Alg ICV'=ICV? ICV ICV Integrity Alg Preamble PLCP Header MAC Header Payload CRC Encrypted IV (4) K-ID Cyphertext ICV (4) EncryptionWired Equivalent Privacy - how it works • IV is incremented per frame, and is transmitted in clear text • IV and Secret Key are concatenated and fed into the WEP engine, which produces a continues random data string • Clear text is XOR-ed with the output of the WEP engine and transmitted as payload • In parallel an ICV is used to generate a “frame check” alike control

  9. EncryptionKey management Station-side • Encryption keys need to be set on AP-1000 / AP-500 and Station side. • Up to 4 keys can be stored at a given time. • One key is used as transmission key indicated by the “active key index” • The other keys can be used as additional receive keys to support key roll-over • To communicate: • Common key value needs to be present at the same key-index number • Key index travels in front of encrypted text (see previous slide) • AP-1000 / AP-500 can accept non-encrypted data when “deny non-encrypted data” box is not checked AP-1000 / AP-500-side

  10. AP Key used for xmission Station(s) A A-0-0-0 A-0-0-0 A-0-0-0 A-0-0-0 A A A-B-0-0 A-0-0-0 A A-B-0-0 A-0-0-0 B A-B-0-0 A-B-0-0 B 0-B-0-0 0-B-0-0 0-B-0-0 0-B-0-0 B EncryptionKey management - roll-over example • Main life for key A • AP uses key A for its transmission • Stations use key A for their transmissions • Transition from key A to key B • AP uses key A for its transmission • (as not all stations may have changed to key B yet) • New key will be transmitted (in encrypted form) and • activated in the station at login (part of script) • Some stations will use key A, if they have not • received the new key • Stations that have received the new key will use it. • Main life for key B • AP uses key B for its transmission • Stations use key B for their transmissions

  11. AP Key used for xmission Station(s) A-0-0-0 A A-0-0-0 A-0-0-0 A A-0-0-0 A-B-0-0 A A-B-0-0 A-B-0-0 B A-B-0-0 0-B-0-0 B 0-B-0-0 0-B-0-0 B 0-B-0-0 0-B-C-0 B 0-B-C-0 0-B-C-0 C 0-B-C-0 0-0-C-0 C 0-0-C-0 0-0-C-0 C 0-0-C-0 0-0-C-D C 0-0-C-D 0-0-C-D D 0-0-C-D 0-0-0-D D 0-0-0-D 0-0-0-D D 0-0-0-D A-0-0-D D A-0-0-D A-0-0-D A A-0-0-D EncryptionKey management - complete roll-over cycle

  12. EncryptionKey Distribution in large networks Following tools are required: • Tool to change a defined key to encrypted form for storage in the registry of a client device • Windows tool called “setcrypt” • Tool only present at one location • Tool to accept the encrypted key and store it in the registry • Tools are present on each client station (after driver installation): • wcluc48.exe - Win/2000/98 • wcluc41.exe - Win/95 • wcluc52.exe - Win/NT

  13. EncryptionKey Distribution in large networks • Process: • Network administrator defines the encryption key(s) • Network administrator changes the APs to use the new keys • Network administrator modifies login script to include a key update routine • Key update utility requires (as command line parameter) the new key(s) in encrypted form for storage on the client station • Key update utility is executed on the client stations as part of the login script

  14. EncryptionUsing Gold and Silver cards in one network • Silver and Gold Cards have different encryption capability: • Silver Card: short key (64 bit) • Gold Card: long key (128 bit) • Using a mix of Gold and Silver cards require: • Gold Card in the AP • Use of 2-3 encryption keys • All transmissions from the AP to the client station use short keys. • Silver cards transmit use short keys to transmit. Can be the same as AP’s transmit key, or can be different one. • Gold cards can transmit using long keys. However the data from the AP to the station will be encrypted using a short key. So a station equipped with a Gold card uses different keys for transmit and receive

  15. MAC Address AuthenticationAccess Control - AP based filter Table • List of ORiNOCO H/W (MAC) addresses, that are allowed access to the backbone through the AP • Maximum number of entries: 497 • Implemented in the AP-1000 / AP-500, not in the PC Card (i.e. not in the AP) • Protects against un-authorized access of the backbone, not against un-authorized access of a PC in the same cell • Access Control table only can only be filled with “Universal MAC addresses” • When non-defaults addresses are used at the station, only “local MAC addresses” can be used

  16. MAC Address AuthenticationAccess Control - AP based filter Table • Creation of Access Control Table • Use ORiNOCO AP Manager to enter MAC addresses • When completed save file at secure location • Maintain Access Control Table • Use ORiNOCO AP Manager to open the Access Control table • Add/Change/Remove entries in the table • Activating Access Control • Use ORiNOCO AP Manager to open the configuration file of a AP • Import the saved table • Restore the configuration file

  17. Radius Server Distribution System 802.11 LAN STA (B) STA (C) STA (A) MAC Address AuthenticationAccess Control - RADIUS based • Extension to existing Access Control system to make it more usable for large networks • Access Control table does not reside in each AP-1000 / AP-500 but in a RADIUS server: • Server device that communicates with APs using RFC 2138 defined RADIUS protocol definition. (RADIUS = Remote Authentication Dial-In User Service) • Network administrator needs to manage one Access Control table which rather then one for each AP • RAC will overcome the limitation of the 497 entries that a AP based Access Control Table can hold at maximum

  18. MAC Address AuthenticationAccess Control - RADIUS based • During Association Process, exchange between AP and Radius Server excutes : • Access Request (containing the Station’s ORiNOCO PC Card MAC address as data) • Access Response (Accepted, when the MAC address is in the Access Control list, or Reject otherwise) • Station is not granted access to the network if it has not been “accepted” (even though it is associated with the AP) • Roaming to another AP and associates with this AP for the 1st time, the RADIUS authentication needs to be re-executed • Roaming to an AP where it has been before, where the “authentication” status is known, re-authentication by the RADIUS server is not needed

  19. Radius Radius Server Server Distribution System 802.11 LAN STA (B) STA (C) STA (A) MAC Address AuthenticationAccess Control - RADIUS based • The system supports two RADIUS servers for back-up: • When the primary server is down, the secondary will be consulted • If no RADIUS servers are available: • Access will not be granted to unknown users (initial requests) • Access will be granted to users that have been authenticated earlier • The AP will execute re-authorizations on periodic basis to “disconnect” stations who have been removed from the database

  20. MAC Address AuthenticationAccess Control - RADIUS based (AP setup) • Enable the AP to execute the RADIUS protocol: • Identify the IP addresses of the primary and secondary RADIUS servers • Select the Authentication Port number (1645 or 1812), being the UDP port that is used by the RADIUS server • Authorization Lifetime, specifying the interval between “automatic re-authorization” • Authorization Password, used as • user password in association with the MAC address of the Station • Shared secret to allow the AP to determine validity of the RADIUS server

  21. Clients File IP address of AP (1) - Shared Secret IP address of AP (2) - Shared Secret ….. ….. IP address of AP (n) - Shared Secret Users File Username MAC -1 Password =“Shared Secret” Username MAC -2 Password =“Shared Secret” ….. ….. Username MAC -n Password =“Shared Secret” MAC Address AuthenticationAccess Control - RADIUS based (Server setup) RADIUS server contains 2 major files • Clients file containing data on the APs attached to the RADIUS server: • IP Address (or Host-name) of the AP • Password (same as “Authorization Password” entered during the AP configuration) • Users file: • User name (being the MAC address of the ORiNOCO PC Card) • Format of the MAC address: AABBCC-DDEEFF • Password (same as “Authorization Password” entered during the AP configuration)

  22. IEEE 802.1x SecurityPort-based Network Access Control • IEEE 802.1x - Port Based Network Access Control • Standard to address the requirement to restrict access to LANs (and their connected services) to those users that are permitted to use the LAN • Still in draft (version 11 is out for working-group comments) • Primary focus is authentication of wired ports, extended to apply to wireless • Uses Extensible Authentication Protocol (PPP-EAP, defined in RFC) and applies it over LAN • Standard addresses Authentication and not encryption • Regular WEP encryption is required for wireless

  23. A controlled port An uncontrolled port Authenticator System services This port is used for exchanging Protocol info with The supplicant Authenticator PAE EAP And EAPOL Protocol exchanges Frame is Available to Both ports Authentication Server Supplicant PAE EAP Protocol exchanges LAN IEEE 802.1x SecurityPort-based Network Access Control • Standard defines terms such as: • Port Access Entity (PAE) • the mechanism (algorithms and protocols) associated with a LAN port (residing in either a Bridge or a Station) • Supplicant PAE • The entity that requires authentication before getting access to the LAN (typically in the client station) • Authenticator PAE • The entity facilitating authentication of a supplicant (typically in bridge or AP) • Authentication Server • The entity that provides authentication service to the Authenticators in the LAN (could be a RADIUS server)

  24. A controlled port An uncontrolled port Authenticator System services This port is used for exchanging Protocol info with The supplicant Authenticator PAE EAP And EAPOL Protocol exchanges Frame is Available to Both ports Authentication Server Supplicant PAE EAP Protocol exchanges LAN IEEE 802.1x SecurityPort-based Network Access Control • Standard addresses the concept of Controlled and Uncontrolled ports • Uncontrolled Port • Logical entity in the Bridge or AP • Provides access to single network resource: The Authentication Server • Access through the un-controlled port does not allow access to other network resources • Controlled Port • Analogous to a door that opens once Authentication has been positively completed • Allows access to all other network resources allowed for the user

  25. Windows 2000 Advanced Server (with RADIUS) Authentication server EAP over RADIUS EAP over LAN (EAPOL) IP Networks AP-2000 Authenticator Supplicant IEEE 802.1x SecurityAs implemented by ORiNOCO products • The AP-2000 is the Authenticator • The RADIUS Server in the WIN2K Adv. Server is the Authentication server • A client with Win/XP is the supplicant • The AP-2000 acts as relay for traffic between client station and RADIUS server through its uncontrolled port • Uses encapsulation of EAP when using the respective path: • EAPOL - EAP over LAN (EAP frames encapsulated in IEEE802.11 frames) • EAP over RADIUS (EAP frames encapsulated in the RADIUS Request/Response protocol)

  26. IEEE 802.1x SecurityDetailed exchange Client Station AP-2000 RADIUS Server • A wireless station associates to its AP • The AP will issue an EAP Request Identity frame to the client station • The client station responds with its identity (machine name or user name) • The AP relays the EAP message (I.e. client station’s identity) to the RADIUS server, to initiate the authentication services • The authentication protocol between the RADIUS server and the client station is known as TLS (Transport Level Security) • The RADIUS server requests credentials from for the client station to to confirm the identity, by sending the EAP request via the AP • The client replies sending its credentials relayed by the AP 802.11 Association Network Access Blocked EAPOL EAP over RADIUS EAP Request Identity EAP Response (Identity) EAP Response (Identity) EAP Request (TLS Start) EAP Request (TLS Start) EAP Response (TLSClient_hello) EAP Response (TLSClient_hello)

  27. Client Station AP-2000 RADIUS Server EAPOL EAP over RADIUS EAP Request (TLS Server_hello, TLS Cert) EAP Request (TLS Server_hello, TLS Cert) EAP Response (TLSCert, key exchg) EAP Response (TLSCert, key exchg) EAP Request (TLS chgcipher spec) EAP Request (TLS chgcipher spec) EAP Response (TLS) EAP Response (TLS) IEEE 802.1x SecurityDetailed exchange • The “TLS_Hello” messages are the start of the TLS handshake protocol: • Client initiates by sending its Client_hello (including so-called Cyphersuite, indicating what crypto algorithm it can handle) • Server replies with Server_Hello, stating among other what crypto-algorithm was selected, and requesting the client to send its certificate • The client will send its certificate after the Hello handshake is completed, and initiates the “Key-Exchange” sequence (Diffie Hellman)

  28. Client Station AP-2000 RADIUS Server EAPOL EAP over RADIUS EAP Success (TLS Session key) EAP Success (TLS Session key) Network Access Enabled EAP Key (WEP Key) WEP set in PC Card via NDIS OIDs IEEE 802.1x SecurityDetailed exchange • On completion of the DH Key exchange between server and client, the server transmits its keys to the AP-2000. • The AP-2000 will generate a WEP key-pair to be used by the client and the AP for further transmissions between client and AP. • The AP-2000 will transmit this key pair to the client and uses the key received from the server to encrypt this message • Once the client received the WEP keys it will pass them to the PC card via the NDIS interface and the driver • Station and AP will use these WEP keys until station logs off or until re-authentication timer has expired (for period re-authentication) • When station roams to another AP new WEPs are established. (No TLS exchange required)

  29. Module summary • Spread Spectrum • Network Name / Closed System • Authentication • WEP Encryption • MAC address based Access Control • IEEE 802.1x Security

  30. Your Mobile Broadband Connection

More Related