312-50V11 · Question #325
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. DH groups define the modulus (prime) bit length used during the key exchange, and group 5 specifically uses a 1536-bit modulus.
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
(47 responses)- A2% (1)
- B2% (1)
- C89% (42)
- D6% (3)
Why each option
DH groups define the modulus (prime) bit length used during the key exchange, and group 5 specifically uses a 1536-bit modulus.
768-bit corresponds to DH Group 1, not Group 5.
1025-bit is not a defined DH group size; no standard group uses this value.
Diffie-Hellman Group 5 is defined in RFC 3526 as using a 1536-bit MODP (Modular Exponential) prime. This is a well-established standard where each group number maps to a fixed bit length - Group 1 is 768-bit, Group 2 is 1024-bit, Group 5 is 1536-bit, and Group 14 is 2048-bit.
2048-bit corresponds to DH Group 14, not Group 5.
Concept tested: Diffie-Hellman group key sizes and standards
Source: https://www.rfc-editor.org/rfc/rfc3526
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