Hi Jafar, section 2.10 of IKEv2 RFC 7296 [1] states that
Nonces used in IKEv2 MUST be randomly chosen, MUST be at least 128 bits in size, and MUST be at least half the key size of the negotiated pseudorandom function (PRF). However, the initiator chooses the nonce before the outcome of the negotiation is known. Because of that, the nonce has to be long enough for all the PRFs being proposed. This is why strongSwan generates nonces with a constant size of 32 bytes (256 bits) as defined in nonce_payloads.h [2] /** * Nonce size in bytes for nonces sending to other peer. */ #define NONCE_SIZE 32 Best regards Andreas [1]https://tools.ietf.org/html/rfc7296#section-2.10 [2]https://git.strongswan.org/?p=strongswan.git;a=blob;f=src/libcharon/encoding/payloads/nonce_payload.h;h=ee8ad17f789ed4fe6a2e3476fc710b79d74885aa;hb=HEAD#l30 On 13.09.2017 20:37, Jafar Al-Gharaibeh wrote: > Hi, > > What is the default length of the nonce used to establish and rekey > IKE/Child SAs? is that based on the DH group? and is the length > configurable? > > Thanks, > Jafar ====================================================================== Andreas Steffen andreas.stef...@strongswan.org strongSwan - the Open Source VPN Solution! www.strongswan.org Institute for Networked Solutions HSR University of Applied Sciences Rapperswil CH-8640 Rapperswil (Switzerland) ===========================================================[INS-HSR]==