Public bug reported:

While enabling NTRU (that was ok) I thought I should also enable BLISS
which is for the same post-quantum use cases. See bug 1863749.

But I got an info from upstream there:
Tobias Brunner (tobias-strongswan) wrote on 2020-03-05: #14
Enabling the bliss Plugin is probably not such a good idea. There is a 
potential local side-channel attack on strongSwan's BLISS implementation 
(https://eprint.iacr.org/2017/505).

The ntru plugin should be fine. However, using NTRU with IKEv2 is not
standardized (uses an algorithm identifiers from the private use range
etc.).

Multiple IKEv2 protocol extensions are currently being developed, for
instance, additional exchanges to use fragmentation during the key
exchange or using multiple and more generic key exchanges, in
particular, post-quantum key encapsulation mechanisms (KEM, of which
most have quite large public keys). The latter (plus signature
algorithms) are currently being standardized by NIST
(https://csrc.nist.gov/projects/post-quantum-cryptography/post-quantum-
cryptography-standardization) and versions of NTRU are among the
contenders in round 2 (https://csrc.nist.gov/projects/post-quantum-
cryptography/round-2-submissions). BLISS is not, but CRYSTALS-DILITHIUM
is designed by the same people. It might be a while until strongSwan
supports the protocol extensions (there is a branch with a partial
implementation) and especially the new algorithms (we currently use the
liboqs library in said branch, https://github.com/open-quantum-
safe/liboqs/).


---

Based on that lets drop BLISS again and keep just NTRU.

** Affects: strongswan (Ubuntu)
     Importance: High
         Status: Triaged

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https://bugs.launchpad.net/bugs/1866765

Title:
  disable BLISS for known side-channel attack

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