312-50V9 · Question #99
Diffie-Hellman (DH) groups determine the strength of the key used in the key exchange process. Which of the following is the correct bit size of the Diffie-Hellman (DH) group 5?
The correct answer is C. 1536 bit key. Diffie-Hellman groups are predefined prime modulus sizes used during IKE key exchange, with each group number corresponding to a specific bit length.
Question
Diffie-Hellman (DH) groups determine the strength of the key used in the key exchange process. Which of the following is the correct bit size of the Diffie-Hellman (DH) group 5?
Options
- A768 bit key
- B1025 bit key
- C1536 bit key
- D2048 bit key
How the community answered
(57 responses)- A2% (1)
- B4% (2)
- C88% (50)
- D7% (4)
Why each option
Diffie-Hellman groups are predefined prime modulus sizes used during IKE key exchange, with each group number corresponding to a specific bit length.
768 bits corresponds to DH Group 1, the weakest and oldest group, not Group 5.
1025 bits is not a valid standard DH group size; no defined DH group uses this modulus.
DH Group 5 uses a 1536-bit modulus, making it stronger than Group 1 (768-bit) and Group 2 (1024-bit). Knowing the correct group size is essential for configuring IPsec/IKE policies, as mismatched groups between peers will prevent tunnel establishment.
2048 bits corresponds to DH Group 14, which is stronger than Group 5 and defined in RFC 3526.
Concept tested: Diffie-Hellman group modulus bit sizes
Source: https://www.cisco.com/c/en/us/support/docs/security-vpn/ipsec-negotiation-ike-protocols/217432-configure-ike-version-2-ikev2-for-site.html
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