1. WEB Security

2. Information securityInformation 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
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3. 3 aspects of information security3 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.
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4. 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.

5. Internet security issuesInternet 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
6

6. 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
7

7. 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
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8. Categories
 Authentication
 Access control
 Data Confidentiality
 Data Integrity
 Nonrepudiation
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9. 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
10

10. 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
11

11. Specific services
 Nonrepudiation
(12) Nonrepudiation, origin
(13) Nonrepudiation, destination
(14) Availability service
Protect to ensure availability
Depends on
- Proper management & control of system resources
12

12. Security mechanisms
(Specific)
 Encipherment
 Digital signature
 Access control
 Data integrity
 Authentication exchange
 Traffic padding
 Routing control
 Notarization
13

13. Security mechanisms
(Pervasive)
 Trusted functionality
 Security label
 Event detection
 Security audit trail
 Security recovery
14

14. Security AttacksSecurity Attacks
15

15. Security AttacksSecurity 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
16

16. 17

17. Methods of DefenceMethods 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
20

18. 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

19. 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

20. Security mechanisms in the
TCP/IP protocol stack

21. 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

22. IPv4 Header

23. IPv6 Header

24. 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

25. 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

26. 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

27. IP Security Scenario

28. 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

29. 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

30. IPSec Services
 Access Control
 Connectionless integrity
 Data origin authentication
 Rejection of replayed packets
 Confidentiality (encryption)
 Limited traffic flow confidentiallity

31. IPSec protocols
 Authentication header (AH)
 Encapsulating security payload (ESP)
 ESP with Authentication

32. 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

33. 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

34. 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.
Security services

35. Before applying AH

36. Transport Mode (AH
Authentication)

37. Tunnel Mode (AH
Authentication)

38. ESP Encryption and Authentication

39. ESP Encryption and
Authentication

40. Combinations of Security
Associations

41. Combinations of Security
Associations

42. Combinations of Security
Associations

43. Combinations of Security
Associations

44. 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

45. 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

46. SSL Architecture

47. SSL connection
 A logical client/server link
 A peer-to-peer connection with two
network nodes.
 Transient.
 Every connection associated with one
session.

48. 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.

49. 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.

50. 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.

51. 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

52. SSL Record Protocol Operation

53. SSL Record Format

54. 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

55. Alert protocol
 Conveys SSL alerts to peer
 Payload of record
 Consists of two bytes
1st
byte : warning or fatal
2nd
byte: code for specific alerts

56. SSL Record Protocol Payload

57. 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.

58. handshake protocol phases
 1st
phase
Establish security capabilities
 2nd
phase
Server authentication and key exchange
 3rd
phase
Client authentication and key exchange
 4th
phase
finish

59. Handshake Protocol Action

60. Full handshake

61. Re-establish old session

62. 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

63. 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 )

65. 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))||

66. 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))||…..

67. 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)

68. 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.

69. SET Services
 Provides a secure communication
channel in a transaction.
 Provides tust by the use of X.509v3
digital certificates.
 Ensures privacy.

70. SET Overview
 Key Features of SET:
Confidentiality of information
Integrity of data
Cardholder account authentication
Merchant authentication

71. SET Participants

72. 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

73. Sequence of events for
transactions
1. The customer opens an account.
2. The customer receives a certificate.
3. Merchants have their own certificates.
4. The customer places an order.
5. The merchant is verified.
6. The order and payment are sent.
7. The merchant request payment authorization.
8. The merchant confirm the order.
9. The merchant provides the goods or service.
10. The merchant requests payments.

74. Dual Signature
H(OI))]||)(([ PIHHEDS cKR=

75. Payment processing
Cardholder sends Purchase Request

76. Payment processing
Merchant Verifies Customer Purchase Request

77. Payment processing
 Payment Request:
Initiate request
Initiate response
Purchase request
Purchase response
 Payment Authorization:
Authorization Request
Authorization Response
 Payment Capture:
Capture Request
Capture Response

78. 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

79. 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

80. 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

81. 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