Category Archives: Crypto

BIND DNSSEC Signing

DNSSEC Signing w/ BIND

To solve the chicken-or-egg problem for DNSSEC from the other side, let’s use an authoritative DNS server (BIND) for signing DNS zones. This tutorial describes how to generate the keys and configure the “Berkeley Internet Name Domain” (BIND) server in order to automatically sign zones. I am not explaining many details of DNSSEC at all, but only the configuration and verification steps for a concrete BIND server.

It is really easy to tell BIND to do the inline signing. With this option enabled, the admin can still configure the static database for his zone files without any relation to DNSSEC. Everything with signing and maintaining is fully done by BIND without any user interaction. Great.

Continue reading DNSSEC Signing w/ BIND

F5 Single DH use

F5 SSL Profile: “Single DH use” not working?

In the paper of the Logjam attack, a sentence about the F5 load balancers confused me a bit: “The F5 BIG-IP load balancers and hardware TLS frontends will reuse g^{b} unless the “Single DH” option is checked.” This sounds like “it does NOT use a fresh/ephemeral diffie-hellman key for new connections”. I always believed, that when a cipher suite with EDH/DHE is chosen, the diffie-hellman key exchange always generates a new b for computing g^{b}. Hm.

Therefore, I tested this “Single DH use” option on my lab F5 unit, in order to find out whether the same public key (as noted in Wireshark) is used for more than one session.

Continue reading F5 SSL Profile: “Single DH use” not working?

Elliptic-Curve

Site-to-Site VPNs with Diffie-Hellman Groups 19 & 20 (Elliptic Curve)

Similar to my test with Diffie-Hellman group 14 shown here I tested a VPN connection with the elliptic curve Diffie-Hellman groups 19 and 20. The considerations why to use these DH groups are listed in the just mentioned post – mainly because of the higher security level they offer. I tested the site-to-site IPsec connections with a Juniper ScreenOS firewall and a Fortinet FortiGate firewall. (Currently, neither the Palo Alto nor the Cisco ASA support these groups.)

Continue reading Site-to-Site VPNs with Diffie-Hellman Groups 19 & 20 (Elliptic Curve)

F to A-

Palo Alto PANOS 6.1.2: No more SSLv3/POODLE

Another fixed issue in the just released PANOS version 6.1.2 from Palo Alto Networks is bug ID 71321: “Removed support for SSL 3.0 from the GlobalProtect gateway, GlobalProtect portal, and Captive Portal due to CVE-2014-3566 (POODLE).” I scanned my lab unit before (6.1.1) and after the OS upgrade (6.1.2) and here are the results.

Continue reading Palo Alto PANOS 6.1.2: No more SSLv3/POODLE

KeePass-GeneratedPasswords

Considerations about IPsec Pre-Shared Keys

Pre-shared keys (PSK) are the most common authentication method for site-to-site IPsec VPN tunnels. So what’s to say about the security of PSKs? What is its role for the network security? How complex should PSKs be? Should they be stored additionally? What happens if an attacker catches my PSKs?

I am listing my best practice steps for generating PSKs.

Continue reading Considerations about IPsec Pre-Shared Keys

Apache SSL Cipher Suites

Apache SSL Cipher Suites: Perfect Forward Secrecy

I was interested to tune my https sites with Apache to support only cipher suites that use the ephemeral Diffie-Hellman key exchange = perfect forward secrecy. But after searching a while through the Internet, only SSLCipherSuite with a few concrete algorithms were presented, while I wanted to use a more generic option such as known from “!MD5”. Here it is:

Continue reading Apache SSL Cipher Suites: Perfect Forward Secrecy

Site-to-Site VPNs w DH14 featured image

Site-to-Site VPNs with Diffie-Hellman Group 14

When talking about VPNs it is almost always clear that they are encrypted. However, it is not so clear on which security level a VPN is established. Since the Perfect Forward Secrecy (PFS) values of “DH group 5” etc. do not clearly specify the “bits of security”, it is a misleadingly assumption that the security is 256 bits due to the symmetric AES-256 cipher. It is not! Diffie-Hellman group 5 has only about 89 bits of security…

Therefore, common firewalls implement DH group 14 which has a least a security level of approximately 103 bits. I tested such a site-to-site VPN tunnel between a Palo Alto and a Juniper ScreenOS firewall which worked without any problems.

Continue reading Site-to-Site VPNs with Diffie-Hellman Group 14

PFS Featured Image

At a Glance: Perfect Forward Secrecy (PFS)

During the last few months the concept of Perfect Forward Secrecy (PFS) was presented on many newspapers and guidelines. This concept is related to the session key generation for SSL/TLS as well as for IPsec tunnels. And even though many of these articles describe the benefit of PFS, I was still missing a picture that shows the main difference between the classical key exchange via RSA and the exchange via Diffie-Hellman with PFS. So, here comes my poster. 😉

Continue reading At a Glance: Perfect Forward Secrecy (PFS)