8.3.1 Transport layer security

Background:

ISO/IEC 8072, ISO/IEC 8073, ISO/IEC 8602, ISO/IEC 10736, NIST SDNS^8.2 SP4

Communicating entities will be involved in a security association: they will have to share knowledge on how to communicate securely [FOR94, p.262]. This includes both static and dynamic attributes such as the identity of the communicating parties, algorithms used, keys, sequence numbers, etc. It should be noted that some of this information has limited lifetime. A certain package of security mechanism information can be predetermined so that it does not have to be renegotiated for every new security association. Such a package is called an agreed set of security rules or ASSR. ASSRs should not be kept secure and should therefore not include certain information.

ASSRs include the numbers indicating the level of requested security quality-of-service (QOS) used in establishing a secure communication channel. The concept of access labels can map onto QOS requirements, e.g. ``sensitive information'' is expected to be encrypted using export allowed DES, while "top secret" should use higher grade encryption.

TLSP (Transport Layer Security Protocol) security mechanisms provided by SP4 include:

• Security labels (like "top secret", "secret", "public",...)
• Direction indicators (prevent reflection attacks)
• Integrity check values
• Encryption padding (if required by the algorithm)
• Encryption

TLSP security mechanisms already provided by the transport layer are:

• Sequence integrity
• Integrity recovery

Entity authentication (connection oriented communication) or data origin authentication (connectionless communication) happens in 2 stages:

1.

Security association establishment using keys

2.

Entity authentication on connection establishment or origin authentication by knowledge of a key used in the packet encapsulation process.

Peer addresses are checked with the keys used for the authentication process in order to detect masquerade attacks.

Security associations may be established in three different ways: using the security association protocol part of the TLSP, through application layer protocol exchanges or out-of-band. Key management techniques are not standardized, but Authenticated Diffie-Hellman could be used.

Figure B.2 shows the encapsulation process to provide confidentiality and integrity at the level of the transport layer ([ISO95, p.15]).

  

Figure B.2: The security encapsulation process

Footnotes

...

C. Dinkel (Ed.), Secure Data Network System (SDNS) Network, Transport, and Message Security Protocols, U.S. Department of Commerce, National Institute of Standards and Technology, Report NISTIR-90-4250, 1990.

... SDNS^8.2