Post-quantum OpenPGP on Fedora 45: shared setup

This is the shared setup for three client-specific guides:

• KMail
• Claws Mail
• Evolution

The experiment tests hybrid post-quantum OpenPGP mail on Fedora 45 using Sequoia Chameleon as a GnuPG-compatible OpenPGP engine.

Use these constructions:

Signing:    ML-DSA-65+Ed25519   OpenPGP algorithm 30
Encryption: ML-KEM-768+X25519   OpenPGP algorithm 35

A successful UI indication alone is not sufficient evidence. The client-specific guides also inspect the generated OpenPGP packets and independently verify or decrypt the messages.

Architecture at a glance

KMail
  -> QGpgME
  -> GPGME++
  -> patched GPGME
  -> Sequoia Chameleon
  -> Sequoia OpenPGP / Keystore

Claws Mail
  -> PGP/Core + PGP/MIME
  -> patched GPGME
  -> Sequoia Chameleon
  -> Sequoia OpenPGP / Keystore

Evolution
  -> Camel OpenPGP
  -> GnuPG-compatible CLI
  -> Sequoia Chameleon
  -> Sequoia OpenPGP / Keystore

KMail and Claws Mail exercise GPGME and therefore require the experimental RFC 9980 GPGME patch used in this proof of concept. Evolution does not; use Fedora’s stock GPGME package for Evolution.

Install the common components

Enable the COPR and install the Chameleon package:

sudo dnf copr enable stavroskousidis/rfc9980-openpgp-poc

sudo dnf install -y \
  sequoia-chameleon-rfc9980-poc

Install Sequoia sq from Fedora:

sudo dnf install -y sequoia-sq

Check the installed packages:

rpm -q \
  sequoia-chameleon-rfc9980-poc \
  sequoia-sq

Use Sequoia Chameleon 0.13.1 with sequoia-openpgp 2.4.1. Both Fedora sequoia-sq releases used during testing (1.4.1-1.fc45 and 1.4.1-3.fc45) accept the key-generation syntax below.

GPGME: client-specific setup

KMail and Claws Mail

For KMail and Claws Mail, install the experimental GPGME build from the COPR:

sudo dnf upgrade -y \
  --allow-vendor-change \
  --repo="copr:copr.fedorainfracloud.org:stavroskousidis:rfc9980-openpgp-poc" \
  gpgme

Confirm that Fedora installs this build:

gpgme-2.0.1-6.rfc9980.1.fc45.x86_64

The patch adds recognition of the RFC 9980 algorithm IDs needed by the GPGME-based client paths.

Evolution

For Evolution, use Fedora’s stock GPGME:

gpgme-2.0.1-6.fc45.x86_64

If you previously installed the patched build, restore Fedora’s package before testing Evolution:

sudo dnf copr disable stavroskousidis/rfc9980-openpgp-poc

sudo dnf distro-sync -y \
  --allow-vendor-change \
  gpgme

This operation leaves the Chameleon package installed.

Select Chameleon for the desktop session

In a terminal in the normal desktop session:

export PATH="/usr/libexec/rfc9980-openpgp/bin:/usr/bin:/bin"

command -v gpg
command -v gpgconf
command -v gpgsm

gpg --version
gpgconf --list-components

The expected mapping is:

gpg:OpenPGP:/usr/libexec/rfc9980-openpgp/bin/gpg
gpgsm:S/MIME:/usr/bin/gpgsm

This intentionally redirects only the OpenPGP CLI path used by the experiment. Fedora’s gpgsm remains the S/MIME implementation.

Start the mail client from the same terminal session so that it inherits this PATH.

Create a disposable RFC 9980 test certificate

For an isolated test:

mkdir -p "$HOME/rfc9980-mail-test"
cd "$HOME/rfc9980-mail-test"

sq key generate \
  --own-key \
  --userid "RFC9980 PoC <rfc9980-poc@example.invalid>" \
  --profile rfc9580 \
  --cipher-suite mldsa65-ed25519 \
  --encryption-algorithm mlkem768-x25519 \
  --expiration 1d \
  --without-password \
  --output rfc9980-secret.pgp \
  --rev-cert rfc9980.rev

sq inspect rfc9980-secret.pgp

This command uses one explicit User ID containing both the display name and e-mail address. This is the identity form used for the walkthrough because it integrates cleanly with Evolution’s sender-e-mail matching.

Alternatively, generate the certificate with separate name and e-mail User IDs by replacing the --userid option with:

--name "RFC9980 PoC" \
--email "rfc9980-poc@example.invalid"

Choose one identity form; do not create both certificates for the test. Both forms worked with KMail and Evolution in this proof of concept. Evolution integrated more cleanly with the explicit --userid form.

The mail client’s account display name is a separate account setting and does not determine how the OpenPGP certificate’s User ID is encoded.

The command creates a certificate with an ML-DSA-65+Ed25519 primary/signing structure and an ML-KEM-768+X25519 encryption subkey.

Import it into the Sequoia-backed environment:

sq key import rfc9980-secret.pgp

Importing the key makes the certificate available to Sequoia, but does not authenticate its User ID. Because this is a self-generated test identity without an external certification path, explicit authorization is required.

This matters because applications may need more than “a suitable key exists”: they may require a sufficiently authenticated binding between the sender or recipient identity and that key before permitting cryptographic operations.

Authorize the local test identity using the fingerprint printed by sq:

sq pki link authorize \
  --unconstrained \
  --cert=YOUR_FINGERPRINT \
  --all

Check both interfaces:

sq cert list YOUR_FINGERPRINT
gpg --with-colons --list-keys YOUR_FINGERPRINT
gpg --with-colons --list-secret-keys YOUR_FINGERPRINT

The Chameleon view should expose algorithm 30 for the ML-DSA-65+Ed25519 signing-capable key material and algorithm 35 for the ML-KEM-768+X25519 encryption subkey.

The one-day, passwordless key is intentionally disposable and should not be used as a production identity.

Test methodology

In each client, create three messages to:

rfc9980-poc@example.invalid

using:

Unsigned
Signed only
Encrypted + signed

Then inspect the signed and encrypted messages independently and confirm:

signed-only signature packet:
  algorithm 30
  MLDSA65_Ed25519
  GOODSIG
  VALIDSIG
  verification exit status 0

encrypted-and-signed:
  version-6 PKESK
  algorithm 35
  MLKEM768_X25519
  DECRYPTION_OKAY
  decryption exit status 0

inner signature after decryption:
  algorithm 30
  GOODSIG
  VALIDSIG
  verification exit status 0

Results

Client	Desktop	GPGME	Verified
KMail 26.08.1	Fedora 45 KDE Plasma	Experimental patch	Sign ✓ · Encrypt ✓
Claws Mail 4.4.0	Fedora 45 KDE Plasma	Experimental patch	Sign ✓ · Encrypt ✓
Evolution 3.62.0	Fedora 45 GNOME	Fedora stock	Sign ✓ · Encrypt ✓

KMail and Claws Mail use the experimental RFC 9980 GPGME patch. Evolution uses Fedora’s stock GPGME package because Camel invokes the GnuPG-compatible Chameleon CLI directly. Independent verification confirms algorithm 30 and 35 packets with GOODSIG, VALIDSIG, DECRYPTION_OKAY, and exit status 0.

See the client-specific guides for the runtime evidence and message locations.

Scope

Treat this as an experimental interoperability proof of concept, not as a recommendation to replace Fedora’s system OpenPGP stack globally. The COPR packages and compatibility wrapper keep Fedora’s standard GnuPG infrastructure intact and allow side-by-side testing without affecting the rest of the system.