[Manuthor]

Problem

With a server key_encryption_key stored in an HSM, ckms pqc keys create -a ml-kem-768-p256 fails with HTTP 500:

Cryptographic error: Unsupported key format type: ConfigurableKEMSecretKey, for a Transparent EC private key

Hybrid KEM keys (ConfigurableKEM, native X25519MLKEM768 / X448MLKEM1024) are ByteString-only keys with no OpenSSL representation.

Defects fixed

	Defect	File
A	Wrap: NoEncoding sent every private/public key through OpenSSL (breaks Create, Import, ReKeyKeyPair, Export with a KeyWrappingSpecification)	crate/crypto/src/crypto/wrap/wrap_key.rs
B	Unwrap: decode_unwrapped_key did not decode ConfigurableKEM* (breaks Encrypt/Decrypt after restart, default_unwrap_type, NotWrapped export/import)	crate/crypto/src/crypto/wrap/unwrap_key.rs
C	Export rejected any requested KeyFormatType other than PKCS8/Raw, so a ConfigurableKEM key could not be exported with its own format	crate/server/src/core/operations/export_get.rs

Import (D) and is_pqc_algorithm (E) were already fixed on develop by #1268.

Tests

• cargo test -p cosmian_kms_crypto --features non-fips --lib test_wrap_unwrap_byte_string_kem_keys
• tests::hsm::test_hsm_all now runs hybrid_kem_lifecycle (crate/server/src/tests/hsm/hybrid_kem_dek.rs): Create, restart (cold cache, HSM unwrap), GetAttributes, Locate, Export with stored format, Import, default_unwrap_type, ReKeyKeyPair, Encrypt/Decrypt (encapsulate/decapsulate), Revoke, Destroy for ml-kem-512-p256, ml-kem-768-p256 and X25519MLKEM768.

export SOFTHSM2_CONF=/tmp/softhsm2-kms/softhsm2.conf
mkdir -p /tmp/softhsm2-kms/tokens && echo "directories.tokendir = /tmp/softhsm2-kms/tokens" > "$SOFTHSM2_CONF"
SLOT=$(softhsm2-util --init-token --free --label my_token_1 --so-pin 12345678 --pin 12345678 | grep -o 'reassigned to slot [0-9]*' | awk '{print $4}')
HSM_MODEL=softhsm2 HSM_USER_PASSWORD=12345678 HSM_SLOT_ID=$SLOT SOFTHSM2_PKCS11_LIB=/opt/homebrew/lib/softhsm/libsofthsm2.so \
  cargo test -p cosmian_kms_server --features non-fips -- tests::hsm::test_hsm_all --ignored --exact

Notes

• The commit was made with pre-commit hooks skipped (authorised by the maintainer): cargo deny check fails on a RUSTSEC advisory for ctutils 0.4.2 already present in develop's Cargo.lock.
• ConfigurableKEM private keys are sensitive by default, so a plain export of them is denied by design; the SoftHSM2 test creates non-sensitive pairs.
• 5.22.1 PR: fix(server): HSM-wrapped hybrid KEM key lifecycle (5.22.1) #1329