Standards and Protocols

1
Standards and Protocols

• Chapter 7

2
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.

3
Key Terms

• Certificate
• Certificate Authority (CA)
• Certificate Revocation List (CRL)
• Internet Security Association and Key Management
  Protocol (ISAKMP)
• IPsec
• Pretty Good Privacy (PGP)
• Public key infrastructure (PKI)
• Secure/Multipurpose Internet Mail Extensions
  (S/MIME)
• Secure Sockets Layer (SSL)

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Key Terms (continued)

• Transport Layer Security (TLS)
• Wired Equivalent Privacy (WEP)
• Wireless Application Protocol (WAP)
• Wireless Transport Layer Security (WTLS)
• X.509

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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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Relationships Between PKI Standards and Protocols
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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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The PKIX Model
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PKIX Standard

• PKIX working group addresses five major areas
• Outlines certificate extensions and content not
  covered by X.509 v3 and the format of version
• Provides certificate management message formats
  and protocols, defining the data structures,
  management messages, and management functions for
  PKIs
• Outlines certificate policies and certification
  practices statements (CPSs), establishing the
  relationship between policies and CPSs
• Specifies operational protocols, defining the
  protocols for certificate handling
• Includes time-stamping and data certification and
  validation services

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Attribute Certificates and Qualified Certificates

• Attribute Certificate (AC) is used to grant
  permissions using rule-based, role-based, and
  rank-based 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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The PKIX PMI Model
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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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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 Diffie-Hellman key-agreement protocol
PKCS 4 Incorporated into PKCS 1, no longer active
PKCS 5 Password-Based Cryptography Standard Definition of a password-based 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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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 technology-independent programming interface for cryptographic devices
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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
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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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X.509 Certificate Components
Field Name Field Description
Certificate Signature X.509 version used for this certificate Version 1 0, Version 2 1, Version 3 2
Serial Number 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.
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X.509 Certificate Components (continued)
Validity Not valid before time Not valid after time Validity specifies a period of time during which the certificate is valid, using a not valid before time and a not valid after 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 3a unique bit-string identifier for the CA that issued the certificate.
Subject Unique ID Optional for versions 2 and 3a unique bit-string identifier for the subject of the certificate.
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X.509 Certificate Components (continued)
Extension ID Critical Extension Value Optional for version 3the 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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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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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
  networksby encrypting network connections at the
  transport layer

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SSL/TLS

• TLS SSL are not interchangeable TLS is the
  more modern of the two.
• TLS is superior to SSL since SSLs 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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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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TLS Handshake Protocol
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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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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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ISAKMP Header Format
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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.

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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

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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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XKMS Tier 0 Retrieval
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XKMS Tier 1 Retrieval
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XKMS Tier 2 Locate Service
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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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IETF S/MIME v3 Specifications

• Includes specifications for all the following
• Cryptographic Message Syntax (CMS)
• S/MIME v3 message specification
• S/MIME v3 certificate-handling specification
• Enhanced security services (ESS) for S/MIME

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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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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
  creators 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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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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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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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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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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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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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 its easy to configure.

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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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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.

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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

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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

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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.