Session keys that are derived from preshared keys are safe to quantum attacks if the preshared keys are endowed with sufficient entropy. Therefore, the resulting system is deemed secure against classical attackers of today, and against future quantum attackers.

RFC 8784 (Mixing Preshared Keys in IKEv2 for Postquantum Security) outlines an enhancement to the IKEv2 protocol that renders it quantum-computer-resistant through the incorporation of preshared keys, referred to as PPKs. This RFC establishes the specifications for enabling PPK capability negotiation, PPK ID transmission, the integration of PPK as a supplementary factor in session key derivation, and the potential fallback to sessions not dependent on PPKs.

The Cisco Secure Key Integration Protocol (SKIP) is an HTTPS-driven protocol designed to enable encryption devices like routers to import PPKs from an external key source. These externally imported PPKs, referred to as dynamic PPKs, provide advantages such as automated provisioning and updates, and improved PPK entropy. Encryption devices must have the SKIP client and the external key source must have the SKIP server.

To be SKIP-compliant, an external key source must follow the Cisco SKIP protocol and use an out-of-band synchronization mechanism. This ensures that the same PPK is provided to both the initiator and responder encryption devices. The external key source can be in the form of a Quantum Key Distribution (QKD) device, software, or cloud-based key source or service.

The external key source must meet the following expectations to be SKIP-compliant:

• Must implement the SKIP protocol or API, as specified in the Cisco SKIP specification.

• Must provide the same PPK to the encryption device pair—initiator and responder—using an out-of-band synchronization mechanism.

Note	Key source vendors, such as QKD vendors, must contact their Cisco representative to implement the Cisco SKIP protocol.

The following figure shows quantum-safe IKEv2 and OTNsec session keys using dynamic PPK.

The IKEv2 initiator and responder are connected to their respective local key sources and are configured with the SKIP client that specifies the IP address and port of the key source. The PPK sources are also configured with the SKIP parameters, which include the local key source identity and a list of identities of the peer key sources.

The high-level operation of Cisco SKIP protocol is as follows:

1. The IKEv2 initiator places a request for a PPK from its key source. The key source replies with a PPK and the corresponding PPK ID.

2. The initiator-side key source synchronizes the PPK to the responder-side key source using an out-of-band mechanism that is specific to the type of key source. The IKEv2 initiator communicates the PPK ID to the IKEv2 responder over IKEv2 using the RFC 8784 extensions.

3. The IKEv2 responder requests from its key source, the PPK corresponding to the PPK ID received from the IKEv2 initiator. The key source replies with the PPK corresponding to the PPK ID.

4. The IKEv2 initiator and responder mix the PPK in the key derivation, as specified in RFC 8784. The resulting IKEv2 and OTNsec session keys are quantum-safe.

You can also use another easier way known as manual PPKs. When using the manual PPKs, you can provision the same PPKs on both the IKEv2 and OTNsec initiator and responder by manually configuring the PPKs on both sides.

Ensure that a manual PPK is of sufficient size, entropy, and is frequently rotated by the administrator.

In the following figure, you can see the session keys of quantum-safe IKEv2 and OTNsec, which are obtained through a manual PPK.

From Release 24.3.1, the Type 6 password is supported on the PPK and preshared key used in the keyring configuration for the IKEv2 encryption. The Type 6 method uses a user-configured primary key to encrypt sensitive configurations, such as the preshared key, using the Advanced Encryption Standard (AES256-GCM) method. This primary key is stored in Trusted-Anchor-Module (TAM) and is never displayed in the configuration, ensuring that the Type 6 method is more secure and that the encrypted configuration is highly protected.

Use the show ikev2 sa detail command to display information about the current IKEv2 security associations. The Quantum resistance parameter in the output of the commnd indicates that manual PPK-based quantum-safe encryption is enabled.

Note	Both manual and dynamic PPK options can be used for viewing IKEv2 details.

RP/0/1/CPU0:ios#show ikev2 sa detail

IKE SA ID                             : 866
-------------------------------------------------------------------------------
 Local                                : 192.0.2.34/500
 Remote                               : 192.0.2.40/500
 Status(Description)                  : READY (Negotiation done)
 Role                                 : Initiator
 Fvrf                                 : Default
 Encryption/Keysize                   : AES-CBC/256
 PRF/Hash/DH Group                    : SHA512/SHA512/19
 Authentication(Sign/Verify)          : PSK/PSK
 Life/Active Time(sec)                : 86400/21
 Session ID                           : 5
 Local SPI                            : C18D2946B0C4259C
 Remote SPI                           : 5D1BD398AEB3A1E1
 Local ID                             : 192.0.2.34
 Remote ID                            : 192.0.2.40
 Quantum resistance                   : Enabled with manual PPK

Use the show ikev2 statistics command to display the statistics and counters related to IKEv2 sessions.

RP/0/1/CPU0:ios#show ikev2 statistics  
Thu Jun  8 13:30:06.360 IST

................................

NO_NAT                        :        2               0               0               0        

PPK COUNTERS
=============================================================================================

PPK ERRORS
---------------------------------------------------------------------------------------------
PPK_ID_MISMATCH               :        0        
PPK_RETRIEVE_FAIL             :        0        
PPK_AUTH_FAIL                 :        0

Use the show ikev2 summary command to display the IKEv2 session summary of NCS 1014.

RP/0/1/CPU0:ios#show ikev2 summary 
Thu Jun  8 12:54:30.969 IST

IKEv2 SA Summary
-------------------------------------------------
Total SA (Active/Negotiating)         : 2 (2/0)
Total Outgoing SA (Active/Negotiating): 2 (2/0)
Total Incoming SA (Active/Negotiating): 0 (0/0)
Total QR SA (Dynamic/Manual)          : 2 (1/1)

Use the show ikev2 profile command to display all the IKEv2 profile details.

RP/0/1/CPU0:ios#show ikev2 profile 
Tue Jun  6 18:00:20.277 IST

Profile Name                          : p4
===============================================================================
Keyring                               : k4
Fvrf                                  : Default
Lifetime(Sec)                         : 86400
DPD Interval(Sec)                     : 4
DPD Retry Interval(Sec)               : 2
Match ANY                             : NO
Total Match remote peers              : 1
   Addr/Prefix                        : 198.51.100.19/255.255.255.0
Number of Trustpoints                 : 0
Local auth method                     : PSK
Number of remote auth methods         : 1
   Auth Method                        : PSK
PPK Keyring                           : Not Configured

Profile Name                          : ppk_d
===============================================================================
Keyring                               : Not Configured
Fvrf                                  : Default
Lifetime(Sec)                         : 86400
DPD Interval(Sec)                     : 4
DPD Retry Interval(Sec)               : 2
Match ANY                             : NO
Total Match remote peers              : 0
Number of Trustpoints                 : 0
Local auth method                     : NULL
Number of remote auth methods         : 0
PPK Keyring                           : ppk_d

Profile Name                          : ppk_m
===============================================================================
Keyring                               : Not Configured
Fvrf                                  : Default
Lifetime(Sec)                         : 86400
DPD Interval(Sec)                     : 4
DPD Retry Interval(Sec)               : 2
Match ANY                             : NO
Total Match remote peers              : 0
Number of Trustpoints                 : 0
Local auth method                     : NULL
Number of remote auth methods         : 0
PPK Keyring                           : ppk_m

Use the show keyring command to display the configured keyring details on NCS 1014.

RP/0/1/CPU0:ios#show keyring 
Tue Jun  6 18:00:28.272 IST

Keyring Name                          : k4
===============================================================================
Total Peers                           : 1
-------------------------------------------------------------------------------
   Peer Name                          : init
   IP Address                         : 198.51.100.19
   Subnet Mask                        : 255.255.255.0
   Local PSK                          : Configured
   Remote PSK                         : Configured
   PPK Mode                           : Not Configured
   PPK Mandatory                      : Not Configured

Keyring Name                          : ppk_m
===============================================================================
Total Peers                           : 1
-------------------------------------------------------------------------------
   Peer Name                          : init
   IP Address                         : Not Configured
   Subnet Mask                        : Not Configured
   Local PSK                          : Not Configured
   Remote PSK                         : Not Configured
   PPK Mode                           : Manual
   PPK Mandatory                      : No


Keyring Name                          : ppk_m_req
===============================================================================
Total Peers                           : 1
-------------------------------------------------------------------------------
   Peer Name                          : init
   IP Address                         : Not Configured
   Subnet Mask                        : Not Configured
   Local PSK                          : Not Configured
   Remote PSK                         : Not Configured
   PPK Mode                           : Manual
   PPK Mandatory                      : Yes


Keyring Name                          : ppk_d
===============================================================================
Total Peers                           : 1
-------------------------------------------------------------------------------
   Peer Name                          : init
   IP Address                         : Not Configured
   Subnet Mask                        : Not Configured
   Local PSK                          : Not Configured
   Remote PSK                         : Not Configured
   PPK Mode                           : Dynamic
   PPK Mandatory                      : No


Keyring Name                          : ppk_d_req
===============================================================================
Total Peers                           : 1
-------------------------------------------------------------------------------
   Peer Name                          : init
   IP Address                         : Not Configured
   Subnet Mask                        : Not Configured
   Local PSK                          : Not Configured
   Remote PSK                         : Not Configured
   PPK Mode                           : Dynamic
   PPK Mandatory                      : Yes