Web security pot

Cryptography and
Cryptography and
Network Security
Network Security
Chapter 17
Chapter 17
Fourth Edition
Fourth Edition
by William Stallings
by William Stallings
Lecture slides by Lawrie Brown
Lecture slides by Lawrie Brown
Chapter 17 – Web Security
Chapter 17 – Web Security
Use your mentality
Use your mentality
Wake up to reality
Wake up to reality
—
—
From the song, "I've Got You under
From the song, "I've Got You under
My Skin“ by Cole Porter
My Skin“ by Cole Porter
Web Security
Web Security

Web now widely used by business,
Web now widely used by business,
government, individuals
government, individuals


but Internet & Web are vulnerable
but Internet & Web are vulnerable

have a variety of threats
have a variety of threats

integrity
integrity

confidentiality
confidentiality

denial of service
denial of service

authentication
authentication

need added security mechanisms
need added security mechanisms
SSL (Secure Socket Layer)
SSL (Secure Socket Layer)

transport layer security service
transport layer security service

originally developed by Netscape
originally developed by Netscape


version 3 designed with public input
version 3 designed with public input

subsequently became Internet standard
subsequently became Internet standard
known as TLS (Transport Layer Security)
known as TLS (Transport Layer Security)

uses TCP to provide a reliable end-to-
uses TCP to provide a reliable end-to-
end service
end service

SSL has two layers of protocols
SSL has two layers of protocols
Where SSL Fits
Where SSL Fits
SSL Architecture
SSL Architecture
SSL Architecture
SSL Architecture

SSL connection
SSL connection

a transient, peer-to-peer, communications link
a transient, peer-to-peer, communications link

associated with 1 SSL session
associated with 1 SSL session


SSL session
SSL session

an association between client & server
an association between client & server

created by the Handshake Protocol
created by the Handshake Protocol

define a set of cryptographic parameters
define a set of cryptographic parameters

may be shared by multiple SSL connections
may be shared by multiple SSL connections
SSL Record Protocol Services
SSL Record Protocol Services

message integrity
message integrity

using a MAC with shared secret key
using a MAC with shared secret key

similar to HMAC but with different padding
similar to HMAC but with different padding

confidentiality
confidentiality


using symmetric encryption with a shared
using symmetric encryption with a shared
secret key defined by Handshake Protocol
secret key defined by Handshake Protocol

AES, IDEA, RC2-40, DES-40, DES, 3DES,
AES, IDEA, RC2-40, DES-40, DES, 3DES,
Fortezza, RC4-40, RC4-128
Fortezza, RC4-40, RC4-128

message is compressed before encryption
message is compressed before encryption
SSL Record Protocol
SSL Record Protocol
Operation
Operation
SSL Change Cipher Spec
SSL Change Cipher Spec
Protocol
Protocol

one of 3 SSL specific protocols which
one of 3 SSL specific protocols which
use the SSL Record protocol
use the SSL Record protocol

a single message
a single message

causes pending state to become

causes pending state to become
current
current

hence updating the cipher suite in use
hence updating the cipher suite in use
SSL Alert Protocol
SSL Alert Protocol

conveys SSL-related alerts to peer entity
conveys SSL-related alerts to peer entity

severity
severity
•
warning or fatal
warning or fatal

specific alert
specific alert
•
fatal: unexpected message, bad record mac,
fatal: unexpected message, bad record mac,
decompression failure, handshake failure, illegal
decompression failure, handshake failure, illegal
parameter
parameter
•
warning: close notify, no certificate, bad certificate,
warning: close notify, no certificate, bad certificate,

unsupported certificate, certificate revoked,
unsupported certificate, certificate revoked,
certificate expired, certificate unknown
certificate expired, certificate unknown

compressed & encrypted like all SSL data
compressed & encrypted like all SSL data
SSL Handshake Protocol
SSL Handshake Protocol

allows server & client to:
allows server & client to:

authenticate each other
authenticate each other

to negotiate encryption & MAC algorithms
to negotiate encryption & MAC algorithms

to negotiate cryptographic keys to be used
to negotiate cryptographic keys to be used

comprises a series of messages in phases
comprises a series of messages in phases
1.
1.
Establish Security Capabilities
Establish Security Capabilities
2.
2.

Server Authentication and Key Exchange
Server Authentication and Key Exchange
3.
3.
Client Authentication and Key Exchange
Client Authentication and Key Exchange
4.
4.
Finish
Finish
SSL Handshake Protocol
SSL Handshake Protocol
TLS (Transport Layer
TLS (Transport Layer
Security)
Security)

IETF standard RFC 2246 similar to SSLv3
IETF standard RFC 2246 similar to SSLv3

with minor differences
with minor differences

in record format version number
in record format version number

uses HMAC for MAC
uses HMAC for MAC

a pseudo-random function expands secrets

a pseudo-random function expands secrets

has additional alert codes
has additional alert codes

some changes in supported ciphers
some changes in supported ciphers

changes in certificate types & negotiations
changes in certificate types & negotiations

changes in crypto computations & padding
changes in crypto computations & padding