## What is Diffie-Hellman Group 2?

You specify the Diffie-Hellman group in Phase 2 only when you select Perfect Forward Secrecy (PFS). PFS makes keys more secure because new keys are not made from previous keys. If a key is compromised, new session keys are still secure.

**Is Diffie-Hellman Group 2 secure?**

Using Diffie-Hellman alongside authentication algorithms is a secure and approved solution. Diffie-Hellman public key cryptography is used by all major VPN gateway’s today, supporting Diffie-Hellman groups 1,2, 5, 14 as well as others.

### Which DH groups are secure?

If you are using encryption or authentication algorithms with a 128-bit key, use Diffie-Hellman groups 5, 14, 19, 20 or 24. If you are using encryption or authentication algorithms with a 256-bit key or higher, use Diffie-Hellman group 21.

**What is VPN DH group?**

Diffie-Hellman (DH) allows two devices to establish a shared secret over an unsecure network. In terms of VPN it is used in the in IKE or Phase1 part of setting up the VPN tunnel. There are multiple Diffie-Hellman Groups that can be configured in an IKEv2 policy on a Cisco ASA running 9.1(3).

## How does Diffie-Hellman key exchange work?

In the Diffie–Hellman key exchange scheme, each party generates a public/private key pair and distributes the public key. After obtaining an authentic copy of each other’s public keys, Alice and Bob can compute a shared secret offline. The shared secret can be used, for instance, as the key for a symmetric cipher.

**What is Diffie-Hellman Group Exchange SHA256?**

diffie-hellman-group14-sha256. This key exchange uses the group14 (a 2048-bit MODP group) along with a SHA-2 (SHA2-256) hash. This represents the smallest Finite Field Cryptography (FFC) Diffie-Hellman (DH) key exchange method considered to be secure. It is a reasonably simple transition to move from SHA-1 to SHA-2.

### What is DH Group VPN?

**What does DH stand for and how is it used by IPSec technologies?**

Diffie-Hellman (D-H) is a public-key cryptography protocol. It allows two parties to establish a shared secret key used by encryption algorithms (DES or MD5, for example) over an insecure communications channel. D-H is used within IKE (described later in this article) to establish session keys.

## What is VPN Diffie-Hellman?

Diffie-Hellman (DH) is a public-key cryptography scheme that allows two parties to establish a shared secret over an insecure communications channel. DH public key cryptography is used by all major VPN gateways.

**How do you decrypt Diffie-Hellman?**

Encrypt and decrypt a number

- Select the shared numbers. select a large prime number P.
- Select the private key and share the public key. Let’s look at two users, Alice and Bob.
- Compute the super key for encoding and decoding. Alice computes her super key as X = B^a mod P.
- Use the superkey to encrypt and decrypt.

### How does the Diffie-Hellman exchange work during Phase 2?

When you specify PFS during Phase 2, a Diffie-Hellman exchange occurs each time a new SA is negotiated. The DH group you choose for Phase 2 does not need to match the group you choose for Phase 1. For branch office VPN tunnels and BOVPN virtual interfaces, the default DH group for both Phase 1 and Phase 2 is Diffie-Hellman Group 14.

**What are Diffie-Hellman (DH) groups?**

Diffie-Hellman (DH) groups determine the strength of the key used in the key exchange process. Within a group type (MODP or ECP), higher Diffie-Hellman group numbers are usually more secure.

## What is the difference between DH groups 21 and 24?

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?”

**What is dh2f steel used for?**

Classified as a “free-machining” steel. Ideal for complex, precision molds and parts susceptible to distortion and/or deformation without needing additional heat-treating. Ideal for Ion-nitriding. DH2F has a machine rating of 65 out of 100, with 100 being the best rating for pre-hardened mold steels.