Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
Standards and Protocols
Chapter 7
© 2010
Principles of Computer Security:
CompTIA Security+® and Beyond, Second 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.
© 2010
Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
Key Terms
• Certificate
•
• Certificate Authority (CA)
•
• Certificate Revocation
List (CRL)
•
• Internet Security
Association and Key
Management Protocol
(ISAKMP)
•
• IPsec
© 2010
Pretty Good Privacy
(PGP)
Public key infrastructure
(PKI)
Secure/Multipurpose
Internet Mail Extensions
(S/MIME)
Secure Sockets Layer
(SSL)
Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
Key Terms (continued)
•
•
•
•
•
© 2010
Transport Layer Security (TLS)
Wired Equivalent Privacy (WEP)
Wireless Application Protocol (WAP)
Wireless Transport Layer Security (WTLS)
X.509
Principles of Computer Security:
CompTIA Security+® and Beyond, Second 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
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
Relationships Between PKI Standards and
Protocols
© 2010
Principles of Computer Security:
CompTIA Security+® and Beyond, Second 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.
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
The PKIX Model
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
PKIX Standard
• PKIX working group addresses five major areas:
1. Outlines certificate extensions and content not covered by X.509 v3
and the format of version
2. Provides certificate management message formats and protocols,
defining the data structures, management messages, and
management functions for PKIs
3. Outlines certificate policies and certification practices statements
(CPSs), establishing the relationship between policies and CPSs
4. Specifies operational protocols, defining the protocols for certificate
handling
5. Includes time-stamping and data certification and validation services
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
Attribute Certificates and Qualified
Certificates
• Attribute Certificate (AC) is used to grant
permissions using rule-based, role-based, and rankbased access controls.
– ACs are used to implement a privilege management
infrastructure (PMI).
• Qualified Certificate (QC) is based on European
Commission term used to identify certificates with
specific legislative uses.
– The PKIX QC profile indicates a certificate used to identify
a specific individual with a high level of assurance in a
nonrepudiation service.
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
The PKIX PMI Model
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second 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.
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second 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
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
15 Public Key Cryptography Standards
(continued)
Standard
Title and Description
PKCS #7
Cryptographic Message Syntax Standard: Definition of the
cryptographic message standard for encoded messages, regardless of
encryption algorithm
PKCS #8
Private-Key Information Syntax Standard: Definition of a private key
information format, used to store private key information
PKCS #9
Selected Attribute Types: Definition of attribute types used in other
PKCS standards
PKCS #10
Certification Request Syntax Standard: Definition of a syntax for
certification requests
PKCS #11
Cryptographic Token Interface Standard: Definition of a technologyindependent programming interface for cryptographic devices
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
15 Public Key Cryptography Standards
(continued)
Standard
Title and Description
PKCS #12
Personal Information Exchange Syntax Standard: Definition of a format
for storage and transport of user privates keys, certificates, and other
personal information
PKCS #13
Elliptic Curve Cryptography Standard: Description of methods for
encrypting and signing messages using elliptic curve cryptography
PKCS #14
Cryptographic Message Syntax Standard: Definition of the
cryptographic message standard for encoded messages, regardless of
encryption algorithm
PKCS #15
Cryptographic Token Information Format Standard: Definition of a
format for storing cryptographic information in cryptographic tokens
© 2010
Principles of Computer Security:
CompTIA Security+® and Beyond, Second 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.
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second 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.
© 2010
Principles of Computer Security:
CompTIA Security+® and Beyond, Second 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.
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second 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.
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
Certificates Authorities (CA)
• The root CA issues its own certificate.
• Certificates can be traced through a path to the root CA.
• Each entity that is issued a certificate must be uniquely
identifiable.
• CAs determine what identifier is unique.
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second 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
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second 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.
• TLS is composed of two parts.
– TLS Record Protocol
– TLS Handshake Protocol
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second 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.
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
TLS Handshake Protocol
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
Internet Security Association and Key
Management Protocol (ISAKMP)
• Provides a method for implementing a key
exchange protocol and for negotiating a
security policy
• Defines procedures and packet formats to
negotiate, establish, modify, and delete security
associates
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
ISAKMP (continued)
• ISAKMP supports SAs at all layers of the
network stack.
• A Security Association (SA) is a relationship in
which two or more entities define how they will
communicate securely through a two step
process:
– Entities agree on how to secure messages
– Entities determine the SAs for protocols to be used
for remainder of communications
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
ISAKMP Header Format
© 2010
Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
Certificate Management Protocol (CMP)
• A protocol to obtain X.509 certificates in a PKI.
• Provides the following certificate operations:
– CA establishment, including creation of the initial
CRL and export of the public key for the CA
– Certification of an end-entity
• CMP also defines mechanisms for performing
these operations, either online or offline using
files, e-mail, tokens, or web operations.
© 2010
Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
The XML Key Management
Specification XKMS
• Defines services to manage PKI operations
within XML
• Used for authentication and verification of
electronic signatures
• Allows certificates to be managed, registered, or
revoked
• Services accessible via XML protocol, which is
often easier to interface with than PKI
© 2010
Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
The XML Key Management
Specification XKMS (continued)
• Functions on three tiers of service:
– Tier 0 is the retrieval method; provides a means for
retrieving key information by embedding references
to the key within the XML signature.
– Tier 1 is called the locate service; XKMS serves as a
relay between the client and the PKI.
– Tier 2 is called the validate service; XKMS is actively
involved in verifying the relation between the PKI
information and the document containing the XML
signature.
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
XKMS Tier 0 Retrieval
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
XKMS Tier 1 Retrieval
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
XKMS Tier 2 Locate Service
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
Secure/Multipurpose Internet Mail
Extensions (S/MIME)
• Provides a way to send and receive encrypted
and signed mime data.
• Undergone several revisions, most recent
completed in 2004 by IETF and requires:
– Requires the use of Advanced Encryption Standard
(AES)
• Frequent changes have made the standard
difficult to implement.
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
IETF S/MIME v3 Specifications
• Includes specifications for all the following:
–
–
–
–
© 2010
Cryptographic Message Syntax (CMS)
S/MIME v3 message specification
S/MIME v3 certificate-handling specification
Enhanced security services (ESS) for S/MIME
Principles of Computer Security:
CompTIA Security+® and Beyond, Second 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.
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second 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.
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second 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
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second 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.
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
Certificate Enrollment Protocol (CEP)
• Designed to support certificate issuance,
distribution, and revocation using existing
technologies
– Uses PKCS #7 and PKCS #10 to define common
message syntax
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
Federal Information Processing
Standards Publications (FIPS)
• Describes various standards for data
communication issues.
• Issued through the National Institute of Standards
and Technology (NIST).
• Three main categories of FIPS publications:
– Hardware and software standards/guidelines
– Data standards/guidelines
– Computer security standards/guidelines
• Products sold to U.S. government must comply to
relevant FIPS standards.
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second 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
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
Point-to-Point Tunneling Protocol
(PPTP)
• It allows the encapsulation of one packet inside
another to hide the original packet.
• Its use is widespread and it’s easy to configure.
© 2010
Principles of Computer Security:
CompTIA Security+® and Beyond, Second 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
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Principles of Computer Security:
CompTIA Security+® and Beyond, Second 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.
© 2010
Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
ISO/IEC 27002 - Formerly ISO 17799
• Standard designed for creating and
implementing security policies
• Contains material on 12 subject areas:
– Risk assessment - Determine the impact of risks
– Security policy - Guidance and policy provided by management
– Organization of information security Governance - Structure to
implement security policy
– Asset management - Inventory and classification of assets
– Human resources security - Policies and procedures addressing
security for employees including hire, change, departure
© 2010
Principles of Computer Security:
CompTIA Security+® and Beyond, Second Edition
ISO/IEC 27002 - Formerly ISO 17799
(continued)
–
–
–
–
Physical and environmental security
Communications and operations management
Access control
Information systems acquisition, development, and
maintenance
– Information security incident management
– Business continuity management
– Compliance
© 2010
Principles of Computer Security:
CompTIA Security+® and Beyond, Second 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.
© 2010