Cryptographically Generated Addresses (CGA) Extension Field Format
updates
- rfc-3972 — Cryptographically Generated Addresses (CGA)
Extracted elements (8)
A TLV format was chosen for CGA Extension Fields because multiple mechanisms were anticipated to need inclusion of additional data items in the CGA Parameter Data Structure, and a common TLV encoding simplifies the addition of multiple such data items.
This document updates RFC 3972 by defining a standardized TLV encoding for the Extension Fields already specified in the CGA Parameter Data Structure; implementations of RFC 3972 that use Extension Fields must conform to this encoding.
Data items to be included in Extension Fields of the CGA Parameter Data Structure MUST be encoded using the TLV (Type-Length-Value) format defined in this document.
Extension Data Length is a 16-bit unsigned integer specifying the length of the Extension Data field in octets.
Extension Type is a 16-bit identifier of the type of the Extension Field within the CGA Parameter Data Structure.
IANA created a registry entitled 'CGA Extension Type' for 16-bit unsigned integer values. Future assignments are to be made through Standards Action. Three experimental values are reserved: 0xFFFD (Exp_FFFD), 0xFFFE (Exp_FFFE), and 0xFFFF (Exp_FFFF).
No security concerns are raised by adopting the CGA Extension format itself, but proper security analysis is required when new CGA Extensions are defined to ensure they introduce no new vulnerabilities to existing CGA schemes.
The CGA Extension Field TLV format consists of a 16-bit Extension Type, a 16-bit unsigned integer Extension Data Length (in octets), and a variable-length Extension Data field. The total header overhead is 4 octets.