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Web Security

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  • 1. WEB Security
  • 2. Outline
    • Web Security Considerations
    • Secure Socket Layer (SSL) and Transport Layer Security (TLS)
    • Secure Electronic Transaction (SET)
    • Recommended Reading and WEB Sites
  • 3. Information security
    • Pre computer age
      • Rugged filing cabinets with combination lock
    • Computer age
      • Automated tools for security
    • Computer security
      • Collection of tools to protect data
    • Network security
    • Internet security
  • 4. 3 aspects of information security
    • Security Attack: Any action that compromises the security of information.
    • Security Mechanism: A mechanism that is designed to detect, prevent, or recover from a security attack.
    • Security Service: A service that enhances the security of data processing systems and information transfers. A security service makes use of one or more security mechanisms.
  • 5. Web Security Considerations
    • WWW is Client server application over Internet and TCP/IP intranets
    • Web is vulnerable to attacks on web servers over the Internet
    • The WEB is visible outlet for corporates
    • Web servers are easy to configure and manage.
    • Complex software hide many security flaws.
    • Subverted servers will provide access to intranet systems
    • Users are not aware of the risks.
  • 6. Internet security issues
    • Requirements
      • Confidentiality
      • Authentication
      • Nonrepudiation
      • Integrity
    • Selection of algorithms
    • Services
    • Security mechanisms
      • Creation, distribution and protection of secret keys
      • Dependence of protocol
    • Placement of security mechanisms
  • 7. OSI security architecture
    • ITU-T recommendations X.800
      • Defines a systematic approach
    • International standard
      • For managers to provide security
      • For security products
    • Focuses on services, mechanisms and attacks
  • 8. Security services
    • Definition in RFC 2828
      • A processing or communication service that is provided by a system to give a specific kind of protection to system resources
    • X.800 services
      • Five categories and 14 specific services
  • 9. Categories
    • Authentication
    • Access control
    • Data Confidentiality
    • Data Integrity
    • Nonrepudiation
  • 10. Specific services
    • Authentication
      • (1) Peer entity authentication
      • (2) Data-origin authentication
    • Data confidentiality
      • (3) Connection confidentiality
      • (4) Connectionless confidentiality
      • (5) Selective-field confidentiality
      • (6) Traffic flow confidentiality
  • 11. Specific services
    • Data integrity
      • (7) Connection integrity with recovery
      • (8) Connection integrity without recovery
      • (9) Selective-field Connection Integrity
      • (10) Connectionless Integrity
      • (11) Selective-field Connectionless Integrity
  • 12. Specific services
    • Nonrepudiation
      • (12) Nonrepudiation, origin
      • (13) Nonrepudiation, destination
      • (14) Availability service
          • Protect to ensure availability
          • Depends on
            • Proper management & control of system resources
  • 13. Security mechanisms (Specific)
    • Encipherment
    • Digital signature
    • Access control
    • Data integrity
    • Authentication exchange
    • Traffic padding
    • Routing control
    • Notarization
  • 14. Security mechanisms (Pervasive)
    • Trusted functionality
    • Security label
    • Event detection
    • Security audit trail
    • Security recovery
  • 15. Security Attacks
  • 16. Security Attacks
    • Interruption: This is an attack on availability
    • Interception: This is an attack on confidentiality
    • Modification: This is an attack on integrity
    • Fabrication: This is an attack on authenticity
  • 17.
  • 18.
  • 19.
  • 20. Methods of Defence
    • Encryption
    • Software Controls (access limitations in a data base, in operating system protect each user from other users)
    • Hardware Controls (smartcard)
    • Policies (frequent changes of passwords)
    • Physical Controls
  • 21. Placement of security mechanisms
    • Link to link
      • Hardware device
      • Application unaware
      • Distribution of keys a problem
    • End to end
      • Application/software aware
      • Large no of keys involved
  • 22. Link layer mechanisms
    • Radius (Remote authentication dial in user service)
      • NSA, RADIUS servers
      • Authentication, authorisation, accounting
    • WEP (Wireless encryption Protocol)
      • Static keys
    • WPA (WiFi protected Access)
      • Dynamic keys
  • 23. Security mechanisms in the TCP/IP protocol stack
  • 24. Need for IPSec
    • Application level security services
      • Electronic mail
        • S/MIME, PGP
      • Client Server
        • Kerberos, X.509
      • Web access
        • SSL, TLS, SET
    • Enterprises need security at IP layer
      • To protect security ignorant applications
      • Additional security to applications with security mechanisms
      • Establish private secure network
  • 25. IPv4 Header
  • 26. IPv6 Header
  • 27. IP Security Overview
    • IPSec is not a single protocol.
    • IPSec provides a set of security algorithms
    • IPSec provides a general security framework for a pair of communicating entities
      • Across LAN, Private & Public WANs
      • Across Internet
  • 28. IP Security Overview
    • Applications of IPSec
      • Secure branch office connectivity over the Internet
      • Secure remote access over the Internet
      • Establsihing extranet and intranet connectivity with partners
      • Enhancing electronic commerce security
  • 29. IP Security Overview
    • Benefits of IPSec
      • Better firewall protection
      • Transparent to applications (below transport layer (TCP, UDP)
      • Provide security for individual users
    • IPSec can assure that:
      • A router or neighbor advertisement comes from an authorized router
      • A redirect message comes from the router to which the initial packet was sent
      • A routing update is not forged
  • 30. IP Security Scenario
  • 31. IP Security Architectures
    • Integrated architecture
      • Supported in IPv6
      • Difficult to implement in IPv4
    • Bump in The stack (BITS) for IPv4
      • Between Data link and IP layers
    • Bump in The Wire (BITW)
      • Hardware implementation
  • 32. IPSec RFCs
    • IPSec documents:
      • RFC 2401: An overview of security architecture
      • RFC 2402: Description of a packet authentication extension to IPv4 and IPv6
      • RFC 2406: Description of a packet encryption extension to IPv4 and IPv6
      • RFC 2408: Specification of key managament capabilities
  • 33. IPSec Services
    • Access Control
    • Connectionless integrity
    • Data origin authentication
    • Rejection of replayed packets
    • Confidentiality (encryption)
    • Limited traffic flow confidentiallity
  • 34. IPSec protocols
    • Authentication header (AH)
    • Encapsulating security payload (ESP)
    • ESP with Authentication
  • 35. IPSec modes of operations
    • Transport
      • IPSec protects IP payload
      • IPSec headers added before IP payload
      • No change in IP header
    • Tunnel
      • IPSec protects total IP packet
      • IPSec headers encapsulates IP packet
      • New IP header is created
  • 36. Discussion onTunnel and Transport mode
    • Tunnel mode header order
      • New IP hdr->IPsec hdr->old IP hdr->IP payload
      • BITS or BITW architecture
      • Choice for VPN
    • Transport mode header order
      • IP hdr->IPSec hdr->IP payload
      • IPSec integrated architecture
      • End to End security
  • 37. Security services Protocols Transport Mode SA Tunnel Mode SA AH Authenticates IP payload and selected portions of IP header and IPv6 extension headers Authenticates entire inner IP packet plus selected portions of outer IP header ESP Encrypts IP payload and any IPv6 extesion header Encrypts inner IP packet ESP with authentication Encrypts IP payload and any IPv6 extesion header. Authenticates IP payload but no IP header Encrypts inner IP packet. Authenticates inner IP packet.
  • 38. Before applying AH
  • 39. Transport Mode (AH Authentication)
  • 40. Tunnel Mode (AH Authentication)
  • 41. ESP Encryption and Authentication
  • 42. ESP Encryption and Authentication
  • 43. Combinations of Security Associations
  • 44. Combinations of Security Associations
  • 45. Combinations of Security Associations
  • 46. Combinations of Security Associations
  • 47. SSL and TLS
    • SSL was originated by Netscape
    • TLS working group was formed within IETF
    • First version of TLS can be viewed as an SSLv3.1
  • 48. SSL
    • Make use of TCP
    • Provide reliable end to end secure communication
    • Two layers of protocols
      • Higher layer
        • Handshake
        • change cipher spec
        • Alert
      • Lower layer
        • Record
  • 49. SSL Architecture
  • 50. SSL connection
    • A logical client/server link
    • A peer-to-peer connection with two network nodes.
    • Transient.
    • Every connection associated with one session.
  • 51. SSL session
    • An association between a client and a server
    • Defines a set of parameters such as  algorithms used, session number etc.
    • An SSL session is created by the Handshake Protocol
      • that allows parameters to be shared among the connections made between the server and the client
      • Sessions are used to avoid negotiation of new parameters for each connection.
    • A single session is shared among multiple SSL connections between the client and the server.
    • In theory, it may also be possible that multiple sessions are shared by a single connection, but this feature is not used in practice.
  • 52. SSL session
    • The concepts of a SSL session and connection involve several parameters that are used for SSL-enabled communication between the client and the server. During the negotiations of the handshake protocol, the encryption methods are established and a series of parameters of the Session State are subsequently used within the session.
  • 53. SSL session state
    • A session state is defined by the following parameters:
      • session identifier: this is an identifier generated by the server to identify a session with a chosen client,
      • Peer certificate: X.509 certificate of the peer,
      • compression method: a method used to compress data prior to encryption, 
      • CipherSpec: specifies the bulk data encryption algorithm (for example DES) and the hash algorithm (for example MD5) used during the session,
      • Master secret: 48-byte data being a secret shared between the client and server
      • “ is resumable”: this is a flag indicating whether the session can be used to initiate new connections.
  • 54. SSL connection state
    • The SSL connection state is defined by the following parameters:
      • Server and client random: random data generated by both the client and server for each connection,
      • Server write MAC secret: the secret key used for data written by the server, 
      • Client write MAC secret: the secret used for data written by the client,
      • Server write key: the bulk cipher key for data encrypted by the server and decrypted by the client,
      • Client write key: the bulk cipher key for data encrypted by the client and decrypted by the server,
      • Initialisation vectors: for CBC mode of block cipher
      • Sequence number: sequence numbers maintained separately by the server for messages transmitted and received during the data session.
  • 55. Record protocol
    • Services provided
      • Confidentiality
        • Encryption of payloads using shared secret key obtained from handshake protocol
      • Message Integrity
        • MAC using shared secret key obtained from handshake protocol
  • 56. SSL Record Protocol Operation
  • 57. SSL Record Format
  • 58. Change cipher spec protocol
    • Payload of record protocol
    • Consist of single message
      • Single byte value = 1
    • Purpose of message
      • Cause copy of pending state to current state
      • Updates cipher suite to be used on the current connection
  • 59. Alert protocol
    • Conveys SSL alerts to peer
    • Payload of record
    • Consists of two bytes
      • 1 st byte : warning or fatal
      • 2 nd byte: code for specific alerts
  • 60. SSL Record Protocol Payload
  • 61. Handshake Protocol
    • The most complex part of SSL.
    • Allows the server and client to authenticate each other.
    • Negotiate encryption, MAC algorithm and cryptographic keys.
    • Used before any application data are transmitted.
  • 62. handshake protocol phases
    • 1 st phase
      • Establish security capabilities
    • 2 nd phase
      • Server authentication and key exchange
    • 3 rd phase
      • Client authentication and key exchange
    • 4 th phase
      • finish
  • 63. Handshake Protocol Action
  • 64. Full handshake
  • 65. Re-establish old session
  • 66. Cryptographic computations
    • Shared master secret : 48 byte
    • Creation in 2 stages
      • Pre-master secret exchanged
        • RSA
        • Diffie Hellman
      • Master secret calculated at both ends
    • Use of master secret at client end
      • Client write MAC secret
      • Client write key
      • Client write IV
    • Use of master secret at client end
      • Server write MAC secret
      • Server write key
      • Client write IV
  • 67. Transport Layer Security
    • The same record format as the SSL record format.
    • Defined in RFC 2246.
    • Similar to SSLv3.
    • Differences in the:
      • version number (3.1)
      • message authentication code (HMAC, TLScomressed.version)
      • pseudorandom function ( different from SSL)
      • alert codes ( more in TSL)
      • cipher suites ( fortezza dropped)
      • client certificate types ( fortezza schemes not included)
      • certificate_verify and finished message ( calculation different)
      • cryptographic computations ( different from SSL)
      • Padding ( any amount for total length = Xblock length upto max 255 bytes )
  • 68.  
  • 69. Master secret in SSL
    • Master secret =
    • MD5(pre_master_secret||SHA(“A”||pre_master_secret||ClientHello.random||serverHello.random))||
    • MD5(pre_master_secret||SHA(“BB”||pre_master_secret||ClientHello.random||serverHello.random))||
    • MD5(pre_master_secret||SHA(“CCC”||pre_master_secret||ClientHello.random||serverHello.random))||
  • 70. Key block in SSL
    • Key block =
    • MD5(master_secret||SHA(“A”||master_secret||serverHello.random||ClientHello.random))||
    • MD5(master_secret||SHA(“BB”||pre_master_secret|| serverHello.random||ClientHello.random))||
    • MD5(master_secret||SHA(“CCC”||pre_master_secret|| serverHello.random||ClientHello.random))||…..
  • 71. Master secret and Key block in TLS
    • Master secret =
    • PRF(pre_master_secret, “master secret”, ClientHello.random||serverHello.random)
    • Key block =
    • PRF(master_secret, “key expansion”, Security Parameters.server_random||SecurityParameters.client_random)
    • PRF(secret,label,seed) = P_MD5(S1,label||seed)XOR P_SHA-1(S2,label||seed)
  • 72. Secure Electronic Transactions
    • An open encryption and security specification.
    • Protect credit card transaction on the Internet .
    • Companies involved:
      • MasterCard, Visa, IBM, Microsoft, Netscape, RSA, Terisa and Verisign
    • Not a payment system.
    • Set of security protocols and formats.
  • 73. SET Services
    • Provides a secure communication channel in a transaction.
    • Provides tust by the use of X.509v3 digital certificates.
    • Ensures privacy.
  • 74. SET Overview
    • Key Features of SET:
      • Confidentiality of information
      • Integrity of data
      • Cardholder account authentication
      • Merchant authentication
  • 75. SET Participants
  • 76. SET participants
    • Cardholder: authorised holder of credit card issued by issuer. Interacts with merchants over internet
    • Merchant : Seller of goods over internet
    • Issuer : Bank which issues credit card to card holder.
    • Acquirer : Fin institution which has an account with a merchant, processes card authorisation and payments.
    • Payment gateway: Interfaces between SET and Payment network
    • CA: Issues X.509 certificates to All players
  • 77. Sequence of events for transactions
    • The customer opens an account.
    • The customer receives a certificate.
    • Merchants have their own certificates.
    • The customer places an order.
    • The merchant is verified.
    • The order and payment are sent.
    • The merchant request payment authorization.
    • The merchant confirm the order.
    • The merchant provides the goods or service.
    • The merchant requests payments.
  • 78. Dual Signature
  • 79. Payment processing
    • Cardholder sends Purchase Request
  • 80. Payment processing Merchant Verifies Customer Purchase Request
  • 81. Payment processing
    • Payment Request:
      • Initiate request
      • Initiate response
      • Purchase request
      • Purchase response
    • Payment Authorization:
      • Authorization Request
      • Authorization Response
    • Payment Capture:
      • Capture Request
      • Capture Response
  • 82. Payment Request
    • Initiate request from card holder
      • Request certificates to merchant
      • Incl: Brand of cc, ID req/resp, nonce
    • Initiate response by merchant
      • Response signed by Kr of merchant
      • Incl: Cust nonce, new nonce, trans ID, merchant’s signature certificate, payment gateways key exchange certificate
    • Cardholder
      • verifies merchant and gateway’s certificates
      • Generates
        • OI- ref to order
        • PI – card number, value etc
  • 83. Payment Request
    • Purchase request by card holder
      • Forwarded to payment gateway
        • Incl: EKs[PI+Dual sig+OIMD], EKUch[Ks]
      • To merchant
        • OI+dual sig+PIMD, CH certificate
    • Purchase response by merchant
      • Incl: Trans ID, response block with order ack signed by merchant using Kr, merchant’s signature certificate
    • Card holder
      • Verifies merchant’s signature on response block
  • 84. Payment Authorization
    • Authorization Request to payment gateway from merchant
      • forwarded
        • PI+dual sig+OIMD+EKUch[Ks]
      • Generated
        • Auth block: EKms[SignKrm[Trans ID]]
        • EKUpg[EKms]
      • Certificates
        • Card holder signature key, merchant signature key and merchant key exchange certificates
    • Payment gateway
      • Verifies all certificates, obtains EKms, decrypts auth block, verifies merchant’s sign, verifies dual sign, verifies trans ID, requests and receives an auth from issuer
    • Authorisation response by payment gateway to merchant
      • Auth block:
        • EKpgs[SignKrpg[authorisation]]
        • EKUm[EKpgs]
      • Capture token info:
        • EKpgs[SignKrpg[capture token]]
      • Certificate
        • Gateway’s signature key certifixcate
  • 85. Payment capture
    • Capture Request by merchant to payment gateway
      • Capture req block
        • Amount+Trand ID+token signed and encrypted by merchant
    • This is verified by payment gateway. Req issuer to release payment
    • Capture Response by payment gateway to merchant confirmation of payment
  • 86. Recommended Reading and WEB sites
    • Drew, G. Using SET for Secure Electronic Commerce . Prentice Hall, 1999
    • Garfinkel, S., and Spafford, G. Web Security & Commerce. O’Reilly and Associates, 1997
    • MasterCard SET site
    • Visa Electronic Commerce Site
    • SETCo (documents and glossary of terms)

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