Questions tagged [ipsec]

Internet Protocol Security (IPsec) is a protocol suite for securing Internet Protocol (IP) communications by authenticating and encrypting each IP packet of a communication session. IPsec also includes protocols for establishing mutual authentication between agents at the beginning of the session and negotiation of cryptographic keys to be used during the session.

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“ip xfrm state deleteall” vs “ip xfrm state flush” commands

Please explain the purpose of the following commands and differences between them. ip xfrm state deleteall ip xfrm state flush According to the man page : ip xfrm state deleteall - delete all ...
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47 views

IKEv2 Using Different PSKs

We're setting up some new tunnels and have been told to use IKEv2. I understand that IKEv2 allows different authentication methods, e.g. one side using PSK and the other using a certificate. We don't ...
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how ipsec differentiates between re-transmitted tcp segment and malicious one?

How Ipsec protocol differentiates between re-transmitted TCP segment (which is re-transmitted because the sender didnt get the ACK last time) and a malicious one?
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authby=secret serve as alternative to AH in ipsec.conf

I have employed strongSwan U5.5.1 for installing an IPsec tunnel between two Debian hosts with a firewall in between. My ipsec.conf specifies authby=secret but not ah=. The firewall currently permits ...
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Could IPSec flows be decrypted using PSK [duplicate]

I created an IPSec tunnel between two VMs using StrongSwan. It relies on a Pre-Shared Key. I wonder, if this key is leaked, what could an attacker perform? Would he/she be able to decrypt previous ...
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IPsec installed algorithms

What happens if a laptop and a server don't have a encryption algorithm in common? Does IPSec abort the connection or does it always have default algorithms?
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Ipsec: Is it possible to use both pre-shared keys and pubkeys auth methods at the same time?

So if we have a server configuration with local auth pubkeys and remove psk and at the same time for a client(initiator) a local auth psk and remote pubkey. Something like this. Server - local { ...
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66 views

IP Encryptor and Firewall

Firewalls implement IPsec VPN and perform packet filtering. IP Encryptor, on the other hand implements IPsec VPN and achieve security goals (confidentiality, integrity and authentication). What are ...
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TCP Traffic, SSL or extra Tunnel

I have a situation where we (as a SaaS vendor) are migrating one of our clients away from their local premise to our public SaaS. However as a security concern they want to route all their TCP ...
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Is a security association (SA) implemented in ESP and AH protocols?

I'm reading about security associations. I've understood that a SA is a virtual connection between a client and a sever, in which all the security parameters, such as encryption algorithm, IP origin ...
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193 views

How hard is it to retrieve IKEv2 Server Certificate from the server?

I got access to a VPN via IPsec and IKEv2. The provider gave me a username, a shared secret and a server certificate. Since the certificate was self-signed, the manual came with specific instructions ...
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IPSec Sniff Traffic

I'm wondering if it is possible to Sniff IPSec connections. At the beginning of a connection, the two peers agree on a SA and exchange a PSK or Certificates. What I'm thinking about, is to ...
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Where would I go to use a reliably secure encrypted internet connection?

Lately, I’ve been paying $100 a month for Fios. I’m thinking of canceling this service because I rarely use my internet at home, since I’m at school most of the time and my college offers internet (...
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215 views

Maximum number of certificates generated by a CA

What is the maximum number of certificates that can be generated from a CA? The use case is a VPN using certificate authentication and I would like to know what is the theoretical number of unique ...
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148 views

IKE Phase 1 /w PSK resource?

I can't seem to find a sufficiently detailed resource that describes the IKE phase 1 PSK identity authentication process. They seem to focus on differences between aggressive and main mode while ...
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How can the fact that ESP in IPSec does not provide integrity for the IP address be exploited?

I understand that ESP encrypts data and provides integrity for everything EXCEPT layer 3 (the IP address) and that AH provides integrity for everything but does not encrypt. What are the inherent ...
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62 views

IPsec down with unusual SNMP traffic [closed]

Time to time IPSec tunnel status become down, with unusual SNMP Traffic. when I disable and enable port manually, it become normal. I am using 200E fortigate firewall. Have you any idea or previous ...
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IPsec with PSK: Can PSK be used for passive eavesdroping?

I use a PSK to connect to an IPsec VPN. Let's say an attacker can gain access to my PSK. He can then impersonate me, that much is clear. But would she also be able to decrypt intercepted traffic? ...
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IPSEC connection attempt to rogue server — is my PSK compromised?

I am setting up an IPSec connection between two sites using Ubiquiti EdgeOS-based equipment. Using a DDNS service (a static IP is unavailable from the ISP), they can be found at east.example.net and ...
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3k views

Which PFS Group is recommended for IPSec configuration?

I can't find much information on PFS (Perfect Forward Secrecy) Groups so I'm unsure what to suggest for a secure IPSec configuration. Any suggestions on PFS groups that aren't recommended? What is ...
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183 views

What alternatives to IPSec for diversifyed redundancy?

I need to provide redundancy to an IPSec link between two premises. I would like to have no single point of failure and to diversify technologies. What could I use please? Are the following leads ...
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492 views

Please explain the vulnerability for the pre-shared Key for IKEv1 brute force IPSec

After the vulnerability was released for IPSec IKEv1 PSKs, our organization decided to increase the size and complexity of the PSK. However, upon releasing the new PSK we had a few issues: ...
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505 views

Why doesn't IKEv2 use L2TP?

My guess is that with IPSec/IKEv1, since it doesn't support NAT, you either have to manually configure routes from your machine, or use a layer 2 tunnel (such as l2tp) to talk with devices on the ...
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Do I need Gateway Firewall for IoT network? [closed]

Do I need a gateway firewall to prevent attacks like DoS, if my IoT network can only talk to cloud using IPsec? Even if there is need that can be implemented at cloud. Is there any need for it to ...
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475 views

How to use IPsec Transport mode between two gateways

I have read many comparisons of IPsec Transport vs. Tunnel mode, and there is a clear understanding that when two gateways are exchanging routed traffic they should use Tunnel mode. In other words, ...
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How does Cisco Anyconnect VPN work?

I am looking for a deep down technical explanation of how it works. My understanding is its an SSL VPN and works as follows: - Anyconnect creates a TLS session to the configured remote servers, ...
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344 views

Differentiating between IKEv2 and OpenVPN Traffic

There is a WiFi network that I regularly use, and it seems to be blocking all VPN traffic other than IKEv2. I tested this by downloading many of the free/freemium VPN apps from the Google Play Store ...
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232 views

Is IP address whitelisting useful if the IP address is not “secret”?

I'm working on an application that will have access to API keys supplied by our users. The application makes API calls on behalf of our users. The API we're using allows users to whitelist IP ...
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Disable SSLv3 in IPSec CentosOS

I have been told to shut down support to SSLV3 - TLS 1.0 - TLS 1.1 to all encrypted communications towards external web services. Now, I have an IPSec/CentOS gateway in front of my Data Center.How ...
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417 views

IPsec Transport Mode NAT Traversal Security Risks

The strongSwan FAQ states: NAT-Traversal with IPsec transport mode has some inherent security risks. What kind of security risks is the documentation referring to? (links to other resources are ...
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Why rekey long-lived connections?

Why is rekeying after a certain period of time, or after a certain volume of data transfer, often implemented in modern secure transport protocols such as ESP or TLS? What are the security risks of ...
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288 views

What is meant by IPSec is “transparent”

While reading a guide on IPSec, i came across this sentence: IPSec is transparent to the user and the applications. Can someone please tell me what is meant by being transparent from security view ...
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IP Security (IPsec) vs Public Key Infrastructure (PKI)

I've found the following question on the internet and don't think the answer is right. Which of the following does IPsec use? A) SSL B) AES C) DES D) PKI The given answer is D, PKI ...
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IPSec and traffic mirroring [closed]

I have a VoIP server on which several SIP clients are connected to through IPSec tunnels. This is kind of an automated attendant so I both have RTP and SIP signalling flows. I need to be able to ...
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CHAP vs MS-CHAPv2

I'm setting up an L2TP/IPSec VPN, and I can't find any information about this. MS-CHAPv2 has a known vulnerability that makes cracking it relatively easy. Is CHAP more secure? Does MS-CHAPv2's vuln ...
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How often ciphers are used through an IPSEC session

I’m wondering how often a terminal needs to perform a cryptographic hash (ex: SHA) throughout the lifetime of an IPSEC session where both ends are authenticated using certificates. From what I can ...
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Is ESP without AH considered noncompliant with FIPS 140-2?

I have a CentOS 7.4 box running kernel 3.10 that has the fips=1 parameter defined in the kernel grub statement. If I attempt to add an IPSEC SA with the following command it fails: ip xfrm state ...
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568 views

Question about ipsec prevent SYN flooding attack

how IPSec prevents SYN flooding attacks Like if A is sending packets to B using IPsec. Suppose B’s TCP ack gets lost, and A’s TCP retransmits the packet since it assumes the packet was lost. Will B’s ...
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How you can trust your Router to not steal your private IPSec keys?

I would like to connect to my VPN using IPSec protocol. For that, I need a router or any other device that support it. I found this on eBay: https://www.ebay.com/itm/IPsec-VPN-server-military-secure-...
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What is the Identification Payload of RFC2407 used for in IPsec?

RFC2407 outlines the Identification Payload in section 4.6.2, which appears in the fifth and sixth packets of the Main Mode's SA negotiation when using IKEv1. What is this information used for? From ...
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How does IKE with PSK really work and how secure is it?

There is many articles that describe some exploitation techniques on a VPN with IPSec - IKE-PSK. However, I can't understand how the flaws may exist. Thus, I have some question relating to that: 1) ...
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Why do we need IPSec when we can encrypt data at Application layer?

We can Process encryption of data at application layer according to given key. So why do we need to use IPSec for security ? Lets say I want to send message to other machine over internet. Which one ...
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Diffie Hellman Group Matching to IPSec Encryption Algorithm

I'm looking for help determining acceptable Diffie Hellman (DH) Groups for specific IPSec IKE and ESP Encryption Algorithms. The goal is to choose DH groups that provide adequate protection for the ...
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Behavior of IPSec when receive window gets full [closed]

How does IPSec behave when an incoming package can't be marked received in the receive window without the receive window being moved in such a way that a not-yet received package's spot is pushed out ...
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431 views

Known risks with the old IPSEC Cisco VPN client?

I have a couple of customers who still use the old discontinued/obsolete IPSEC based Cisco VPN client. Obviously it is not a good idea to use software that is no longer supported, but that aside: ...
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222 views

What's the point of the second SA exchange in the Create_Child_SA exchange in IPsec

I have problems understanding why you would negotiate crypto-algorithms in the Create_Child_SA request in a IKEv2. During IKE_SA_INIT you negotiate cryptographic algorithms which I assume (correct me ...
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What encryption/authentication methods to use on our VPN server?

I am in the process of setting up some site-to-site VPN connections between our sites. Our new VPN servers at each site have numerous encryption/authentication methods and I want to know which are ...
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405 views

Is IKE aggressive mode really less secure than main mode?

This guy argues it is not: https://www.youtube.com/watch?v=DuowFgNKAIg I really confused about this. According to him, the only purpose of main mode is to make the peers anonymous, but in order to ...
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685 views

Key exchange during IKE_AUTH phase of IKEv2

This is what a casual IKEv2 handshake looks like : Initiator Responder | ...
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IKEv2 and Dead Peer Detection

Some articles and Websites (Wikipedia and Cisco for instance) claim that unlike IKEv1, IKEv2 provides a support for Dead Peer Detection. However, unlike NAT traversal or DoS attacks for example, the ...