Technical update in the proof of HQC

[gaborit]

Dear all,

We would like to mention that we did a small technical update in the
IND-CPA security proof of HQC and definitions of hard problems.
There was indeed an indistingability issue between Game 3 and 4 of the
proof, coming from a lack of technical update
in the proof after the introduction of truncation in Round 2.

One should note that neither the design, implementation nor parameters
of the scheme
are affected by this modification, only the proof is updated.

The updated specification document is available on our site:

https://pqc-hqc.org/

We would like to thank Tobias Hemmert for pointing this to us.

best,

the HQC team.