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1.6.7 Ensure system wide crypto policy enables post-quantum algorithms

Information

A system-wide crypto policy subpolicy named PQ enables post-quantum and hybrid cryptographic algorithms - hybrid Module-Lattice-Based Key-Encapsulation Mechanism (ML-KEM) key exchange and pure Module-Lattice-Based Digital Signature Algorithm (ML-DSA) signatures. It is applied on top of a base policy, for example DEFAULT:PQ.

The PQ subpolicy is available in newer crypto-policies releases. Where it is available, applying it enables these algorithms with the highest priority for the back-ends that support them (for example OpenSSL, GnuTLS, and NSS for TLS, and, on newer OpenSSH versions, the SSH key exchange).

Cryptographically relevant quantum computers threaten classical public-key algorithms such as RSA, ECDSA, and classical Diffie-Hellman key exchange. An adversary can capture encrypted traffic now and decrypt it once such a computer becomes available - a "harvest now, decrypt later" attack.

Enabling the hybrid post-quantum key exchange provided by the PQ subpolicy protects key exchange against this threat. Because the construction is hybrid - a classical algorithm combined with ML-KEM - the connection is no weaker than the classical algorithm alone, even if one component is later found to be weak.

Solution

- IF - the PQ subpolicy is not available on this release (the file /usr/share/crypto-policies/policies/modules/PQ.pmod does not exist), this recommendation is Not Applicable and the following steps do not apply.

Run the following command to apply the PQ subpolicy on top of the active base policy. Replace DEFAULT with the active base policy if it differs, and include any other subpolicies already in use:

# update-crypto-policies --set DEFAULT:PQ

Run the following command to reboot the system to make your cryptographic settings effective for already running services and applications:

# reboot

Impact:

The PQ subpolicy is only available on crypto-policies releases that ship the PQ module. On releases that predate it, this recommendation is Not Applicable and no change is possible.

The post-quantum key exchange is hybrid (a classical algorithm combined with ML-KEM), so peers that do not support the post-quantum algorithms negotiate the classical algorithm and interoperability is preserved. Post-quantum SSH key exchange additionally requires a recent OpenSSH version; on older OpenSSH the PQ subpolicy affects only the non-SSH back-ends.

See Also

https://workbench.cisecurity.org/benchmarks/27890

Item Details

Category: ACCESS CONTROL, IDENTIFICATION AND AUTHENTICATION, SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|AC-17(2), 800-53|IA-5, 800-53|IA-5(1), 800-53|SC-8, 800-53|SC-8(1), CSCv7|14.4

Plugin: Unix

Control ID: 9cfefd885bb347fa525d7abdf7966ed1060db79fe412b324c632ab5f03fad8f8