Cisco Cisco IOS Software Release 12.4(23)

This section presents the Security Functions implemented by the TOE and the Assurance Measures 
applied to ensure their correct implementation.

This section presents the security functions performed by the TOE and provides a mapping between the 
identified security functions and the Security Functional Requirements that it must satisfy. 

The TOE implements the IETF IPSec protocols (RFCs 2401-2410) to provide confidentiality, 
authenticity and integrity for packet flows transmitted from and received by the TOE. The TOE IPSec 
implementation contains a number of functional components that meet the IPSec TSF.

IPSEC.1 - IPSec Internet Key Exchange (IKE)

IKE authenticates IPSec peers (remote TOEs) using pre-shared keys, RSA keys,

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 or digital certificates. 

It also handles the agreement of secure session keys using the Diffie-Hellman algorithm and negotiates 
the parameters used during IPSec ESP (IPSEC.2)

IKE maintains a trusted channel, referred to as a Security Association (SA), between IPSec peers that is 
also used to manage IPSec connections, including:

The negotiation of mutually acceptable IPSec options between peers, 

The establishment of additional Security Associations to protect packets flows using ESP (as per 
IPSEC.2), and

The agreement of secure bulk data encryption (3DES (168-bit) or AES (128, 192, or 256 bit)) keys 
for use with ESP (IPSEC.2).

The TOE uses ESP to protect packet flows between IPSec peers (instances of the TOE) across 
intervening untrusted networks in accordance with a TOE security policy (TSP). ESP is a method of 
encapsulating IP Packets and provides confidentiality using the 3DES and AES ciphers, integrity and 
authenticity using the MD5 and SHA-1 algorithms, and a mechanism to detect the capture and 
retransmission of packets (replay attacks).

The parameters used by ESP, including session encryption keys, are negotiated via IPSec security 
associations (SAs) established via IKE (IPSEC.1) in accordance with the TSP. Note that security 
associations are unidirectional so that between IPSec peers protecting a packet flow (labelled A and B 
for example) there are at least two SA’s - one from A to B and one from B to A. Each SA, and associated 
session encryption key, has a lifetime, which upon expiry results in a new SA and session encryption key 
being established by the SA peers.

The packet flows between two remote IPSec peers that are to be protected by the TOE are defined by 
way of cryptographic maps (IPSEC.3).

1. Support for RSA public/private key pairs for IKE authentication requires the use of an IPSec hardware 

acceleration module. Models listed as using “Built In” modules do not support RSA public/private key pairs 
for IKE authentication.