In Nov ASA 9. Algorithms marked as AVOID do not provide an adequate security level against modern threats and should not be used to protect sensitive information. It is recommended that these algorithms be replaced with stronger algorithms. Next Generation Encryption NGE is expected to meet the security and scalability requirements of the next two decades.
If you are using encryption or authentication algorithms with a bit key, use Diffie-Hellman groups 5, 14, 19, 20 or If you are using encryption or authentication algorithms with a bit key or higher, use Diffie-Hellman group 21 or Since DH5 is considered to weak. How would increase to a higher DH group with an IPsec tunnel that is already in production?
Changing this would be disruptive so make these changes during a maintenance window. Right now with group 5 you have a bit DH key, this is considered weak. Hope this helps. Pleae rate helpful responses. I also find the following IBM document helpful:. If you are using encryption or authentication algorithms with a key length of bits or greater, use Diffie-Hellman group Notice that it appears the ASA prefers DH Groups 21 through 19 over 24 - perhaps because they are more standard elliptic curve groups while group 24 is an exotic extension to older style "Modular exponentiation group?
Based on this group ordering within ASA ikev2 policy it looks like the ASA may "do the right thing" and choose group 21 over 24 if they appear in the same policy "group" line?
This also makes it appear that network engineers should consider eliminating group 24 from the device config completely if it is not a preferred Diffie Hellman group? I have a question. What is meant by "partial support" on the ASA ? On a with OS version 9. Or am I missing something? Tim Glen posted the appropriate commands above, and they do work on ASA running 9.
Not sure about previous versions of 9. Everything else should be avoided if possible. Buy or Renew. Find A Community.
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Did you mean:. Diffie Hellman Groups. Labels: VPN. Tim Glen. Diffie-Hellman group 20 - bit elliptic curve — Next Generation Encryption. Diffie-Hellman group 21 - bit elliptic curve — Next Generation Encryption.For all of the examples, the following configuration information is used:.
Note that This manual step may not be necessary if IPsec is already enabled on the server. You can change the debug level by adding one or more -d options, such as -ddd. Copy the cacert. If not already installed, install the openswan You can use the svcs grep ipsec command to verify that IPsec is enabled. You can use the -d option of the in. The following steps continue the previous Sun Ray server configuration examples. For the pre-shared examples in this section, you would enter For the certificate examples in this section, you would enter For the pre-shared key examples in this section, choose Manage Preshared Keys to create the pre-shared key:.
To verify if the traffic is being encrypted between the server and the Sun Ray, use a network monitoring tool for example, snoop or tcpdump and confirm that the packets seen are using the ESP protocol.
Configuring OpenSwan IPSec Server
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Diffie–Hellman key exchange
Oracle Solaris Certificates. Sun Ray Client Configuration. Admin GUI Help.It provides a more secure VPN tunnel. The SAs are periodically renegotiated to ensure security. The PFS ensures that the same key will not be generated and used again. Think about a scenario that a private key has compromised by a hacker. The hacker would be able to access the data in network transit which is protected by the same key. If we keep using the same key, all future data will be compromised as well. No future data would have been compromised when using a new key.
If the local configuration does not specify a group, the ASA assumes a default of group2. With PFS, every time a new security association SA is negotiated, a new Diffie-Hellman exchange occurs, which requires additional processing time. On most modem hardware based VPN appliances the overhead is negligible. Here is an example configuration on Cisco ASA.
Here are differences among Group 1, 2 and 5. Group 5 uses the highest bit DH, and is supposed to be more secure than the others. The key takeaway is that if you manage both end of the tunnel, you may enable PFS on both ends. Related Posts.
July 21st, 3 Comments. July 20th, 0 Comments. June 21st, 0 Comments. March 16th, 2 Comments. March 16th, 0 Comments. Most reacted comment. Hottest comment thread. Recent comment authors. Notify of.The notation is integrity[-dhgroup].
For IKEv2, multiple algorithms separated by - of the same type can be included in a single proposal. IKEv1 only includes the first algorithm in a proposal. The daemon adds its extensive default proposal to the configured value. To restrict it to the configured proposal an exclamation mark! Note: As a responder, the daemon defaults to selecting the first configured proposal that's also supported by the peer. By disabling charon. In order to restrict a responder to only accept specific cipher suites, the strict flag!
Available since 5. Some aspects of this changed with 5. Digital signatures are superior in every way to shared secrets. Use the left rightauth parameter instead to define authentication methods.
If traffic is detected between leftsubnet and rightsubneta connection is established. This is equal to deleting a connection from the config file. Relevant only locally, other end need not agree on it. A closeaction should not be used if the peer uses reauthentication or uniqueids checking, as these events might trigger the defined action when not desired. Prior to 5. A value of yes causes the daemon to propose both compressed and uncompressed, and prefer compressed.
A value of no prevents the daemon from proposing or accepting compression. The values clearholdand restart all activate DPD and determine the action to perform on a timeout.
With clear the connection is closed with no further actions taken. The default is none which disables the active sending of DPD messages.
The weak DH and LogJam attack impact on IKE / IPsec (and the *swans)
These are only sent if no other traffic is received. This only applies to IKEv1, in IKEv2 the default retransmission timeout applies, as every exchange is used to detect dead peers. Not supported for IKEv1 connections prior to 5.
The notation is encryption-integrity[-dhgroup][-esnmode]. Defaults to aessha aessha1,3des-sha1 before 5. The daemon adds its extensive default proposal to this default or the configured value. Therefore, a proposal mismatch might not immediately be noticed when the SA is established, but may later cause rekeying to fail.
Valid values for esnmode are esn and noesn. Specifying both negotiates extended sequence number support with the peer, the default is noesn. This may help to surmount restrictive firewalls.Together they provide means for authentication of hosts and automatic management of security associations SA. Most of the time IKE daemon is doing nothing. There are two possible situations when it is activated:. There is some traffic caught by a policy rule which needs to become encrypted or authenticated, but the policy doesn't have any SAs.
IKE daemon responds to remote connection. In both cases, peers establish connection and execute 2 phases:. Note: There are two lifetime values - soft and hard. When SA reaches it's soft lifetime treshold, the IKE daemon receives a notice and starts another phase 2 exchange to replace this SA with fresh one.
If SA reaches hard lifetime, it is discarded. Warning: Phase 1 is not re-keyed if DPD is disabled when lifetime expires, only phase 2 is re-keyed. To force phase 1 re-key, enable DPD. Warning: PSK authentication was known to be vulnerable against Offline attacks in "aggressive" mode, however recent discoveries indicate that offline attack is possible also in case of "main" and "ike2" exchange modes.
General recommendation is to avoid using PSK authentication method. IKE can optionally provide a Perfect Forward Secrecy PFSwhich is a property of key exchanges, that, in turn, means for IKE that compromising the long term phase 1 key will not allow to easily gain access to all IPsec data that is protected by SAs established through this phase 1.
It means an additional keying material is generated for each phase 2. Generation of keying material is computationally very expensive. Exempli gratia, the use of modp group can take several seconds even on very fast computer. It usually takes place once per phase 1 exchange, which happens only once between any host pair and then is kept for long time.
PFS adds this expensive operation also to each phase 2 exchange. Diffie-Hellman DH key exchange protocol allows two parties without any initial shared secret to create one securely.
More on standards can be found here. The same way packets with UDP destination port that are to be delivered locally are not processed in incoming policy check. Warning: Ipsec is very sensitive to time changes. If both ends of the IpSec tunnel are not synchronizing time equally for example, different NTP servers not updating time with the same timestamptunnels will break and will have to be established again.
AH is a protocol that provides authentication of either all or part of the contents of a datagram through the addition of a header that is calculated based on the values in the datagram. What parts of the datagram are used for the calculation, and the placement of the header, depends whether tunnel or transport mode is used.
The presence of the AH header allows to verify the integrity of the message, but doesn't encrypt it. Thus, AH provides authentication but not privacy. Another protocol ESP is considered superior, it provides data privacy and also its own authentication method.A bunch of smart crypto research released a paper describing the LogJam attack. It is a cryptographic attack on weak DiffieHellman groups. It talks about DH in various protocols. It is an interesting read.
The conclusion from the paper is that any DH group smaller than should not be used as even non-nationstate attackers can obtain the resources needed to break these. It involves large scale computing clusters and sieving and doing a lot of heating up the planet. First, a small clarification. IKE is responsible for the secure keying operation that generates symmetric session keys used for the actual packet encryption in the ESP protocol. For the published attack, the only type of groups relevant are the MODP groups.
The ECP groups do not use exponentiation and thus are not vulnerable to factoring primes. Some people still want to use modp DH1 but it has strongly decreased over time.
But people needed it frequently enough to interoperate that the code was added, but disabled per default. Of course, it did not prevent people from patching it back in, which some did. The default IKEv1 modp group for openswan and libreswan was I believe openswan is still using modp and if you are still using openswan, I recommend that you switch ASAP, see this git commit activity comparison.
IKEv2 has seen a very very slow start. The latter is mostly done for fear of compatibility issues. But also to support an upgrade path for all devices.
In April ofas the then release manager of Openswan, we released version 2. No problems emerged after the change, but most likely because simply no one but the certification checkbox people were even testing or running IKEv2 at the time. It introduces new MODP groups not with higher sizes, but just with different primes.
What is IPSec VPN PFS Perfect Forward Secrecy
The justification in the RFC states. The purpose of this document is to provide the parameters and test data for eight additional groups, in a format consistent with existing RFCs. The odd thing is that when I talked to people in the IPsec community, no one really knew why this document was started. Nothing triggered this document, no one really wanted these, but no one really objected to it either, so the document originating from Defense contractor BBN made it to RFC status. We had to support these groups due to demands for RFC compliance and certifications.
And when it comes down to cipher mode attacks, IKE has proven to be far more secure than TLS has been in the last three years. FYI, your web or WordPress server has been infected by malware. I just saw an attack that attempted to guess account credentials from your server:. Your email address will not be published. Save my name, email, and website in this browser for the next time I comment. The justification in the RFC states The purpose of this document is to provide the parameters and test data for eight additional groups, in a format consistent with existing RFCs.
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We're deploying ipsec on embedded devices and getting catastrophic performance from the diffie hellman group in ike. Am I correct to say that is sufficiently secure for use in DH, in this context? That is very unlikely to be before There's no confidentiality requirement so we dont care if someone can decrypt the traffic after 24 hours, as long as they cant re-inject it or tamper with current packets that's fine.
The reason given to use dh is because " is no longer secure". I've nothing against dh but given the performance problem i'm trying to push the group. I dont want to do that if I've missed some problem though. The advice that is insecure relates to long lived year RSA keys.
As DH negotiates short lived 24 hour session keys, DH in group is ok for us. In the use of dh in group, then the resulting shared secret has bits of security which cant be forced for 10 - 15 years. If dh in group is used, then the resulting shared secret is probably safe for a few years.
The RFC which defines dh for ike says it generates more than bits of security. So what is meant by "more than" in the rfc. By default, openssl generates the dh secret as a random number of length equal to the dh shared prime, so i'm thinking it will be at the large end of what the "more than" means. I'm not sure how to verify that though. RSA hasnt been forced yet but is expected to be in near future, probably with months or years of computation.
However, our product will still be in use in 10 years time. Maybe RSA will be easily forceable inas long as it takes more than a day dh is still ok. I'm not saying dh will be a good choice ini'm saying if we choose it today then we wont have to phase it out before The shared secret resulting from our dh is only used for 24 hours.
SA lifetime is 24 hours so we're going to renegotiate our tunnels every 24 hours. That means a new DH secret every 24 hours. So as long as dh cannot be forced in a 24 hour period it's ok for us to use dh As long as we think it will still take more than a day to DH the resulting shared secret of a dh can be forced in maybe a few weeks.
Follow up question, if we use 3des tat needs bits of security, DH should generate twice as many bits as needed, but DH only generates bits. How big a problem is that in practice? We also have the option to modify the negotiation, we could say with dhbut generate the secret in a smaller value space. When you use an asymmetric algorithm like DH, it has a "strength" that relates to the difficulty of breaking through it with the best known attacks.
The best known attacks on DH try to solve discrete logarithm with an index calculus variant that has a lot of common elements with the General Number Field Sievean integer factorization algorithm.