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NSE4 · Question #98

What is IPsec Perfect Forwarding Secrecy (PFS)?.

The correct answer is B. A phase-2 setting that allows the recalculation of a new common secret key each time the. This question asks for the definition of Perfect Forward Secrecy (PFS) in the context of IPsec.

Submitted by khalil_dz· Apr 18, 2026VPN and ZTNA

Question

What is IPsec Perfect Forwarding Secrecy (PFS)?.

Options

  • AA phase-1 setting that allows the use of symmetric encryption.
  • BA phase-2 setting that allows the recalculation of a new common secret key each time the
  • CA `key-agreement' protocol.
  • DA `security-association-agreement' protocol.

How the community answered

(59 responses)
  • A
    5% (3)
  • B
    90% (53)
  • C
    3% (2)
  • D
    2% (1)

Why each option

This question asks for the definition of Perfect Forward Secrecy (PFS) in the context of IPsec.

AA phase-1 setting that allows the use of symmetric encryption.

Symmetric encryption is a core component of both Phase 1 and Phase 2, but PFS is a specific setting within Phase 2 related to key generation, not a broad allowance for symmetric encryption in Phase 1.

BA phase-2 setting that allows the recalculation of a new common secret key each time theCorrect

Perfect Forward Secrecy (PFS) is a Phase 2 setting that ensures a compromise of one session key does not compromise past or future session keys by forcing a new Diffie-Hellman key exchange for each new Phase 2 security association.

CA `key-agreement' protocol.

PFS is not a key-agreement protocol itself; rather, it leverages key-agreement protocols (like Diffie-Hellman) within Phase 2 to achieve forward secrecy.

DA `security-association-agreement' protocol.

PFS is a security feature configured within the security association (SA) agreement process, not an agreement protocol itself.

Concept tested: IPsec Perfect Forward Secrecy (PFS)

Source: https://docs.fortinet.com/document/fortigate/7.4.0/administration-guide/603173/phase-1-settings#Perfect_Forward_Secrecy

Topics

#IPsec#PFS#VPN#Key Exchange

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