Transcript Principles of Computer Security

Principles of Computer Security:
CompTIA Security+
Security+® and Beyond, Third Edition
Standards and Protocols
Chapter 7
© 2012
Principles of Computer Security:
CompTIA Security+
Security+® and Beyond, Third Edition
Objectives
• Identify the standards involved in establishing
an interoperable Internet PKI.
• Explain interoperability issues with PKI
standards.
• Describe how the common Internet protocols
implement the PKI standards.
© 2012
Principles of Computer Security:
CompTIA Security+
Security+® and Beyond, Third Edition
Key Terms
• Certificate
•
• Certificate Authority (CA)
•
• Certificate Revocation
List (CRL)
• IPsec
•
• Secure Sockets Layer
(SSL)
© 2012
Public key infrastructure
(PKI)
Secure/Multipurpose
Internet Mail Extensions
(S/MIME)
Pretty Good Privacy
(PGP)
Principles of Computer Security:
CompTIA Security+
Security+® and Beyond, Third Edition
Key Terms (continued)
•
•
•
•
•
© 2012
Transport Layer Security (TLS)
Wired Equivalent Privacy (WEP) - compromised
Wireless Application Protocol (WAP)
Wireless Transport Layer Security (WTLS)
X.509
Principles of Computer Security:
CompTIA Security+
Security+® and Beyond, Third Edition
Standards and Protocols
• Commercial use of the Internet has been one of the
biggest growth industries since the 1990s.
• Public key infrastructures (PKI) are implemented to
secure transactions online.
• Three categories of standards associated with PKI:
– Standards that define the PKI
– Standards that define the interface between applications
and the underlying PKI
– Other standards
© 2012
Principles of Computer Security:
CompTIA Security+
Security+® and Beyond, Third Edition
Relationships Between PKI Standards and
Protocols
© 2012
Principles of Computer Security:
CompTIA Security+
Security+® and Beyond, Third Edition
PKIX Standard and PKCS
• Two main standards for implementing PKI.
• Both based on X.509 standard.
• PKIX produced by Internet Engineering Task Force
(IETF); interactions and operations have four
component types:
– The user, certificate authority (CA), registration authority
(RA), and the certificate revocation list (CRLs)
• PKCS produced by RSA security.
© 2012
Principles of Computer Security:
CompTIA Security+
Security+® and Beyond, Third Edition
The PKIX Model
© 2012
Principles of Computer Security:
CompTIA Security+
Security+® and Beyond, Third Edition
Public Key Cryptography
Standards (PKCS)
• Public Key Cryptography Standards (PKCS) fills
gaps in standards that existed for implementing
PKI.
• PKCS is composed of 13 active standards and 2
discontinued standards.
© 2012
Principles of Computer Security:
CompTIA Security+
Security+® and Beyond, Third Edition
15 Public Key Cryptography Standards
Standard
Title and Description
PKCS #1
RSA Cryptography Standard: Definition of the RSA encryption standard
PKCS #2
Incorporated into PKCS #1, no longer active
PKCS #3
Diffie-Hellman Key Agreement Standard: Definition of the DiffieHellman key-agreement protocol
PKCS #4
Incorporated into PKCS #1, no longer active
PKCS #5
Password-Based Cryptography Standard: Definition of a passwordbased encryption (PBE) method for generating a secret key
PKCS #6
Extended-Certificate Syntax Standard: Definition of an extended
certificate syntax that was made obsolete by X.509 v3
© 2012
Principles of Computer Security:
CompTIA Security+
Security+® and Beyond, Third Edition
X.509
• X.509 is the portion of the X.500 standard that
addresses the structure of certificates used for
authentication.
• X.509 specifies standard formats for public key
certificates, certificate revocation lists, and
Attribute Certificates.
• Version 3 is the current version of the X.509
standard.
© 2012
Principles of Computer Security:
CompTIA Security+
Security+® and Beyond, Third Edition
X.509 Certificate Components
Field Name
Field Description
Certificate
Signature
Serial Number
X.509 version used for this certificate: Version 1 = 0, Version 2 = 1,
Version 3 = 2
A nonnegative integer assigned by the certificate issuer that must
be unique to the certificate.
Signature
Algorithm
Algorithm
Parameters
(optional)
The algorithm identifier for the algorithm used by the CA to sign the
certificate. The optional Parameters field is used to provide the
cryptographic algorithm parameters used in generating the
signature.
Issuer
Identification for the entity that signed and issued the certificate.
This must be a distinguished name within the hierarchy of CAs.
© 2012
Principles of Computer Security:
CompTIA Security+
Security+® and Beyond, Third Edition
X.509 Certificate Components
(continued)
Validity
Validity specifies a period of time during which the certificate
Not valid before time is valid, using a “not valid before” time and a “not valid after”
Not valid after time
time (expressed in UTC or in a generalized time).
Subject
The name for the certificate owner.
Subject Public Key Info This field consists of an encryption algorithm identifier
followed by a bit string for the public key.
Issuer Unique ID
Optional for versions 2 and 3—a unique bit-string identifier
for the CA that issued the certificate.
Subject Unique ID
Optional for versions 2 and 3—a unique bit-string identifier
for the subject of the certificate.
© 2012
Principles of Computer Security:
CompTIA Security+
Security+® and Beyond, Third Edition
X.509 Certificate Components
(continued)
Extension ID
Critical
Extension
Value
Optional for version 3—the extension area consists of a sequence
of extension fields containing an extension identifier, a Boolean
field indicating whether the extension is critical, and an octet
string representing the value of the extension. Extensions can be
defined in standards or defined and registered by organizations or
communities.
Thumbprint
Algorithm
Parameters
(optional)
This field identifies the algorithm used by the CA to sign this
certificate. This field must match the algorithm identified in the
Signature Algorithm field.
Thumbprint
The signature is the bit-string hash value obtained when the CA
signed the certificate. The signature certifies the contents of the
certificate, binding the public key to the subject.
© 2012
Principles of Computer Security:
CompTIA Security+
Security+® and Beyond, Third Edition
Secure Sockets Layer (SSL) and Transport
Layer Security (TLS)
• Provide secure connections between the client and
server for exchanging information
• Provide authentication and confidentiality of
information transfers
• Provide data integrity and security over networks
by encrypting network connections at the
transport layer
© 2012
Principles of Computer Security:
CompTIA Security+
Security+® and Beyond, Third Edition
SSL/TLS
• TLS & SSL are not interchangeable; TLS is the more
modern of the two.
• TLS is superior to SSL since SSL’s use of hashing
forces a reliance on MD5 rather than SHA1.
• http://tools.ietf.org/html/rfc5246#page-4
• Web Server Software – market share
© 2012
Principles of Computer Security:
CompTIA Security+
Security+® and Beyond, Third Edition
TLS Record Protocol
• TLS Record protocol send data by:
–
–
–
–
–
Fragmenting message data into manageable blocks
Optionally compressing the data
Applying a message authentication code (MAC) to the data
Encrypting the data
Transmitting the results
• Received data is decrypted, verified, decompressed,
and reassembled and sent on to the higher-level
client.
© 2012
Principles of Computer Security:
CompTIA Security+
Security+® and Beyond, Third Edition
TLS Handshake Protocol
© 2012
Principles of Computer Security:
CompTIA Security+
Security+® and Beyond, Third Edition
Pretty Good Privacy (PGP)
• Program used to encrypt and decrypt e-mails
and files
• Provides the ability to digitally sign a message
• How PGP works
– Creator uses encryption program to create a key pair.
• Public key designed to give freely to others
• Private key designed to be known only be the creator
– Messages encrypted by the sender using the recipients
public key.
– The recipients private key is used to decrypt the message.
© 2012
Principles of Computer Security:
CompTIA Security+
Security+® and Beyond, Third Edition
How PGP Works
• PGP uses a variation of the standard public key
encryption process.
– An individual (here called the creator) uses the encryption
program to create a pair of keys.
– One key is known as the public key and is designed to be given
freely to others.
– The other key is called the private key and is designed to be
known only by the creator.
– Individuals who want to send a private message to the creator
encrypt the message using the creator’s public key.
– The algorithm is designed such that only the private key can
decrypt the message, so only the creator will be able to
decrypt it.
© 2012
Principles of Computer Security:
CompTIA Security+
Security+® and Beyond, Third Edition
HTTPS
• Uses SSL to secure Hypertext Transfer Protocol
(HTTP) communications
• Uses TCP port 443
• Supports 40-bit RC4 encryption algorithm and
128-bit encryption
© 2012
Principles of Computer Security:
CompTIA Security+
Security+® and Beyond, Third Edition
IPsec
• Collection of IP security features designed to
introduce security at the network layer
• Optional in IPv4, required in IPv6
• Two types of security service:
– Transport mode can be used to ensure authentication
and confidentiality for data alone.
– Tunnel mode can be used to ensure authentication
and confidentiality for both data and header.
© 2012
Principles of Computer Security:
CompTIA Security+
Security+® and Beyond, Third Edition
Wireless Transport Layer Security
(WTLS)
• Provides security for Wireless Application
Protocol (WAP)
• Implemented due to the limited memory and
processing of WAP-enabled phones
• Implemented in one of three classes:
– Class 1: anonymous authentication
– Class 2: server authentication
– Class 3: server and client authentication
• Class 3 the strongest form of WTLS
© 2012
Principles of Computer Security:
CompTIA Security+
Security+® and Beyond, Third Edition
Wired Equivalent Privacy (WEP)
• Used to protect wireless communications from
being intercepted
• Used to prevent unauthorized access to the
wireless network
• Part of the original 802.11 standard
• WEP 1 supported 64 bit encryption; WEP 2
supports 128 bit encryption
• Both WEP 1 and WEP 2 vulnerable to various
attack vectors
© 2012
Principles of Computer Security:
CompTIA Security+
Security+® and Beyond, Third Edition
WEP Security Issues
• Wireless networking with 802.11 is common.
• WEP is an optional security protocol with
significant issues:
– It uses a 24-bit initialization vector as a seed.
– This allows for more than 16 million vectors.
– At modern networks speeds it does not take long for
initialization vectors to repeat.
– The secret key is only 40 bits, and is also quickly
breakable.
• Some provides use 128-bit WEP but is almost
equally vulnerable.
© 2012
Principles of Computer Security:
CompTIA Security+
Security+® and Beyond, Third Edition
Chapter Summary
• Identify the standards involved in establishing
an interoperable Internet PKI.
• Explain interoperability issues with PKI
standards.
• Describe how the common Internet protocols
implement the PKI standards.
© 2012