System Administration Guide: IP Services

IKE Key Negotiation

The IKE daemon, in.iked, negotiates and authenticates keying material for SAs in a protected manner. The daemon uses random seeds for keys from internal functions provided by the Solaris Operating System. IKE provides perfect forward secrecy (PFS). In PFS, the keys that protect data transmission are not used to derive additional keys. Also, seeds used to create data transmission keys are not reused. See the in.iked(1M) man page.

When the IKE daemon discovers a remote system's public encryption key, the local system can then use that key. The system encrypts messages by using the remote system's public key. The messages can be read only by that remote system. The IKE daemon performs its job in two phases. The phases are called exchanges.

IKE Key Terminology

The following table lists terms that are used in key negotiation, provides their commonly used acronyms, and gives a definition and use for each term.

Table 22–1 Key Negotiation Terms, Acronyms, and Uses

Key Negotiation Term 


Definition and Use 

Key exchange 


The process of generating keys for asymmetric cryptographic algorithms. The two main methods are RSA protocols and the Diffie-Hellman protocol. 

Diffie-Hellman protocol 


A key exchange protocol that involves key generation and key authentication. Often called authenticated key exchange.

RSA protocol 


A key exchange protocol that involves key generation and key transport. The protocol is named for its three creators, Rivest, Shamir, and Adleman. 

Perfect forward secrecy


Applies to authenticated key exchange only. PFS ensures that long-term secret material for keys does not compromise the secrecy of the exchanged keys from previous communications.  

In PFS, the key that is used to protect transmission of data is not used to derive additional keys. Also, the source of the key that is used to protect data transmission is never used to derive additional keys. 

Oakley method 


A method for establishing keys for Phase 2 in a secure manner. This protocol is analogous to the Diffie-Hellman method of key exchange. Similar to Diffie-Hellman, Oakley group key exchange involves key generation and key authentication. The Oakley method is used to negotiate PFS. 

IKE Phase 1 Exchange

The Phase 1 exchange is known as Main Mode. In the Phase 1 exchange, IKE uses public key encryption methods to authenticate itself with peer IKE entities. The result is an Internet Security Association and Key Management Protocol (ISAKMP) security association (SA). An ISAKMP SA is a secure channel for IKE to negotiate keying material for the IP datagrams. Unlike IPsec SAs, the ISAKMP SAs are bidirectional, so only one security association is needed.

How IKE negotiates keying material in the Phase 1 exchange is configurable. IKE reads the configuration information from the /etc/inet/ike/config file. Configuration information includes the following:

The two authentication methods are preshared keys and public key certificates. The public key certificates can be self-signed. Or, the certificates can be issued by a certificate authority (CA) from a public key infrastructure (PKI) organization. Organizations include beTrusted, Entrust, GeoTrust, RSA Security, and Verisign.

IKE Phase 2 Exchange

The Phase 2 exchange is known as Quick Mode. In the Phase 2 exchange, IKE creates and manages the IPsec SAs between systems that are running the IKE daemon. IKE uses the secure channel that was created in the Phase 1 exchange to protect the transmission of keying material. The IKE daemon creates the keys from a random number generator by using the /dev/random device. The daemon refreshes the keys at a configurable rate. The keying material is available to algorithms that are specified in the configuration file for IPsec policy, ipsecinit.conf.