# Which DH groups are secure?

## 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 DH group in IPSec?

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 most secure Diffie-Hellman group?

DH group 1 consists of a 768 bit key, group 2 consists of 1024 bit key, group 5 is 1536 bit key length and group 14 is 2048 bit key length. Group 14 is the strongest and most secure of the ones just mentioned, but there are other key lengths as well.

### Can Diffie-Hellman be used for encryption?

The Diffie–Hellman key exchange method allows two parties that have no prior knowledge of each other to jointly establish a shared secret key over an insecure channel. This key can then be used to encrypt subsequent communications using a symmetric-key cipher.

### Is DH Group 14 secure?

DH with 2048 bits (group 14) has 103 bits of security That is: If a really secure VPN connection is needed, the phase 1 and phase 2 parameters should use at least Diffie-Hellman group 14 to gain 103 bits of security. Furthermore, at least AES-128 can be used, which has a security of almost 128 bits.

Is DH Group 19 secure?

The considerations why to use these DH groups are listed in the just mentioned post – mainly because of the higher security level they offer. 30 (from the “European Network of Excellence in Cryptology”), the bits of security for the elliptic curve groups are the following: Group 19 = 256-bit EC = 128 bits of security.

## How do I make my Diffie-Hellman secure?

There are two methods commonly used to agree on shared secrets: have one party use some long-term asymmetric key to encrypt the secret and send it to the owner of the key (like in an RSA key exchange), or have both parties exchange messages that contribute to the computed shared secret (what we call Diffie-Hellman key …

## What is DH encryption?

The Diffie–Hellman (DH) Algorithm is a key-exchange protocol that enables two parties communicating over public channel to establish a mutual secret without it being transmitted over the Internet. DH enables the two to use a public key to encrypt and decrypt their conversation or data using symmetric cryptography.

Is Diffie-Hellman Group 20 secure?

Algorithms marked as AVOID do not provide an adequate security level against modern threats and should not be used to protect sensitive information. If you are using encryption or authentication algorithms with a 128-bit key, use Diffie-Hellman groups 5, 14, 19, 20 or 24.

### Is Diffie-Hellman Group 24 secure?

RFC 5114 Sec 4 states DH Group 24 strength is about equal to a modular key that is 2048-bits long, that is not strong enough to protect 128 or 256-bit AES, you should stay away from 24.

### Is DH Group 20 secure?

Group 20 = 384-bit EC = 192 bits of security That is, both groups offer a higher security level than the Diffie-Hellman groups 14 (103 bits) or 5 (89 bits).

How do you find the secret key in Diffie-Hellman?

1. k=(YA)XBmodq -> same as calculated by B.
2. Global Public Elements. q ; prime number. α ; α < q and it is primitive root of q.
3. USER A KEY GENERATION. Select Private key XAXA
4. USER B KEY GENERATION. Select Private key XBXB
5. Calculation of Secret Key by A. k=(YB)XAmod q.
6. Calculation of Secret Key by B. k=(YA)XBmod q.

## How strong is a DH Group 24 key?

RFC 5114 Sec 4 states DH Group 24 strength is about equal to a modular key that is 2048-bits long, that is not strong enough to protect 128 or 256-bit AES, so I also mark that as AVOID. RFC 3526 – More Modular Exponential (MODP) Diffie-Hellman groups for Internet Key Exchange (IKE)

## Which Diffie-Hellman group should I use for encryption and authentication?

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 or 24.

What is Diffie Hellman group 24 encryption?

Diffie-Hellman group 24 – modular exponentiation group with a 2048-bit modulus and 256-bit prime order subgroup – Next Generation Encryption Algorithms marked as AVOID do not provide an adequate security level against modern threats and should not be used to protect sensitive information.

### Are there any new changes to the DH groups?

In Nov 2016 ASA 9.6 (x) is available and there are no new changes to the DH Groups. Algorithms marked as AVOID do not provide an adequate security level against modern threats and should not be used to protect sensitive information.

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