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Tue, 03 Feb 2026 05:35:25 -0800 (PST) Date: Tue, 3 Feb 2026 21:32:44 +0800 From: Coiby Xu To: Johannes =?utf-8?B?V2llc2LDtmNr?= Cc: dhowells@redhat.com, dmitry.kasatkin@gmail.com, ebiggers@kernel.org, eric.snowberg@oracle.com, keyrings@vger.kernel.org, linux-crypto@vger.kernel.org, linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org, linux-modules@vger.kernel.org, roberto.sassu@huawei.com, simo@redhat.com, zohar@linux.ibm.com, michael.weiss@aisec.fraunhofer.de Subject: Re: IMA and PQC Message-ID: References: <20260130203126.662082-1-johannes.wiesboeck@aisec.fraunhofer.de> Precedence: bulk X-Mailing-List: linux-modules@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260130203126.662082-1-johannes.wiesboeck@aisec.fraunhofer.de> On Fri, Jan 30, 2026 at 09:31:26PM +0100, Johannes Wiesböck wrote: >Hi all, Hi Johannes, > >we conducted an evaluation regarding PQC use in IMA last year (see [1] for all >details) where we also considered the interplay of different PQC signatures and >file systems (ext4, btrfs, XFS, f2fs). Thanks for sharing this comprehensive study! There are many nuances in this research paper! > >Coiby Xu wrote: > >>According to my experiments done so far, for verification speed, >>ML-DSA-65 is consistently faster than ECDSA P-384 which is used by >>current CentOS/RHEL to sign files in a package. > >Regarding performance, similar to Coiby, we found that all variants of ML-DSA >consistently outperformed ECDSA P-256. Glad to know ML-DSA is also faster than ECDSA P-256! > >>The size of a single ML-DSA-65 signature indeed increases dramatically >>compared with ECDSA P-384 (3309 bytes vs ~100 bytes). But I'm not sure >>it can be a big problem when considering the storage capacity. Take >>latest fresh CentOS Stream 10 x86_64 KVM guest as example, without any >>file system optimization, extra ~189MB disk space is needed if all files >>in /usr signed using by ML-DSA-65 where the disk size is 50G. But I >>don't have enough experience to tell how users will perceive it and I'll >>try to collect more feedback. >> >>For the details of my experiments, you can check >>https://gist.github.com/coiby/41cf3a4d59cd64fb19d35b9ac42e4cd7 >>And here's the tldr; version, >>- Verification Speed: ML-DSA-65 is consistently ~10-12% faster >> at verification than ECDSA P-384 when verifying all files in /usr; >> ML-DSA-65 is 2.5x or 3x faster by "openssl speed" >> >>- Signing Speed: ML-DSA-65 appears ~25-30% slower when signing >> all files in /usr; ML-DSA-65 is 4x or 4.8x slower by "openssl speed" >> >>- Storage overhead: For ML-DSA-65, /usr will increase by 189MB and >> 430MB when there are 27346 and 58341 files respectively. But total >> size of pure IMA signatures are estimated (files x (3309+20) bytes) to >> be ~87MB and ~185MB respectively. > >Two relevant aspects we discovered regard the signature size. TL;DR: > >1. Most file systems need to be tuned to support the larger extended attributes >(signatures) if their size goes above a certain threshold (e.g. enable EA_INODE >in ext4). This influences not only disk usage but overall compatibility between >file systems and PQC signatures. A file system that would not provide the >functionality to store larger extended attributes would be incompatible with >large signatures. > >2. For most smaller signatures (like ML-DSA-44/65), we believe that the overhead >of signatures is actually compensated by fragmentation within the file systems. >For example, ext4 will allocate a full file system block for extended attributes. >As long as the signature size is below this block size, we did not observe less >free space on the file system despite the larger signatures. I think this explains why I didn't see any disk overhead when using ECDSA P-384:) > >Overall, we concluded that ML-DSA-65 provides the best combination of disk >overhead, performance and security level. Performace was good and for all >algorithms with larger signatures than ML-DSA-65, file systems would need to be >tuned. Thanks for summarizing your findings regarding the signature size and also sharing your evaluation! > >>According to >>https://www.ietf.org/archive/id/draft-salter-lamps-cms-ml-dsa-00.html >>ML-DSA-44 is intended to meet NIST's level 2 security category. Will >>NIST level 2 meet users' security requirements? > >Regarding security levels: >For security levels, we referred to NIST IR 8547 ipd [2]. >ECDSA P-256 has a classical security strength of 128bits (P-384: 192bits). >According to [2] Table 3, these levels are met by the different ML-DSA variants. >So, if you are migrating from ECDSA P-384, you need to use at least ML-DSA-65 to >meet the same security strength. This is helpful info! And thanks for sharing the perspective of migration! > >Best regards, >Johannes > >[1] https://www.wsbck.net/publications/pqc-ima.pdf >[2] https://nvlpubs.nist.gov/nistpubs/ir/2024/NIST.IR.8547.ipd.pdf > -- Best regards, Coiby