Provided by: openssl_3.5.0-2ubuntu1_amd64 
NAME
EVP_PKEY-ML-KEM, EVP_KEYMGMT-ML-KEM, EVP_PKEY-ML-KEM-512, EVP_PKEY-ML-KEM-768, EVP_PKEY-ML-KEM-1024,
EVP_KEYMGMT-ML-KEM-512, EVP_KEYMGMT-ML-KEM-768, EVP_KEYMGMT-ML-KEM-1024 - ML-KEM keytype and algorithm
support
DESCRIPTION
The ML-KEM-512, ML-KEM-768, and ML-KEM-1024 keytypes are implemented in OpenSSL's default and FIPS
providers.
Keygen Parameters
No mandatory parameters are required for generating a key pair. To set explicit parameters, use
EVP_PKEY_CTX_set_params() after calling EVP_PKEY_keygen_init().
"seed" (OSSL_PKEY_PARAM_ML_KEM_SEED) <octet string>
Internally, ML-KEM generates keys using a 64-byte random value (seed), which is the concatenation of
the 32-byte d and z parameters described in FIPS 203. This optional parameter can be used to set a
pre-determined seed prior to keypair generation.
Generated keys default to retaining the seed used. The seed is also by default retained when keys
are loaded from PKCS#8 files in the seed format. When available, the seed parameter is also used
during key export and import, with keys (by default) regenerated from the seed even when also
provided on import. See "Provider configuration parameters" below for related controls.
When the seed is retained, it is also available as a gettable parameter, and private key output to
PKCS#8 files will by default include the seed. When the seed was not initially known, or was not
retained, PKCS#8 private key files will contain only the private key in FIPS 203 "dk" format.
"properties" (OSSL_PKEY_PARAM_PROPERTIES) <UTF8 string>
Sets properties to be used when fetching algorithm implementations used for ML-KEM hashing
operations.
Use EVP_PKEY_CTX_set_params(3) after calling EVP_PKEY_keygen_init(3).
Common parameters
In addition to the common parameters that all keytypes should support (see "Common Information
Parameters" in provider-keymgmt(7)), ML-KEM keys keys support the parameters listed below. These are
gettable using EVP_PKEY_get_octet_string_param(3) or EVP_PKEY_get_params(3). They can be initialised via
EVP_PKEY_fromdata(3), and are returned by EVP_PKEY_todata(3) given a suitable selection. Once a public
or private key is configured, it can no longer be modified, nor can another key component be added.
"pub" (OSSL_PKEY_PARAM_PUB_KEY) <octet string>
The public key value.
This parameter is used when importing or exporting the public key value with the EVP_PKEY_fromdata()
and EVP_PKEY_todata() functions. The key length and content is that of the FIPS 203 (Algorithm 16:
ML-KEM.KeyGen_internal) ek public key for the given ML-KEM variant. Initial import aside, this
parameter is otherwise only gettable.
"priv" (OSSL_PKEY_PARAM_PRIV_KEY) <octet string>
The private key value.
This parameter is used when importing or exporting the private key value with the EVP_PKEY_fromdata()
and EVP_PKEY_todata() functions. The key length and content is that of the FIPS 203 (Algorithm 16:
ML-KEM.KeyGen_internal) dk private key for the given ML-KEM variant. Initial import aside, this
parameter is otherwise only gettable.
"encoded-pub-key" (OSSL_PKEY_PARAM_ENCODED_PUBLIC_KEY) <octet string>
Used for getting and setting the encoding of a public key. The key format is that of ek in FIPS 203,
Algorithm 16: ML-KEM.KeyGen_internal. Updates of the public and private key components are only
allowed on keys that are empty. Once a public or private key component is set, no further changes
are allowed. This parameter is gettable and settable (once only).
Provider configuration parameters
See the description of the -provparam option in openssl(1) to learn how to set provider configuration
parameters in the command line tools. See OSSL_PROVIDER_add_conf_parameter(3) to learn how to set
provider configuration options programmatically.
"ml-kem.import_pct_type" (OSSL_PKEY_PARAM_ML_KEM_IMPORT_PCT_TYPE) <UTF8 string>
When an ML-KEM key is imported as an explict FIPS 203 dk decapsulation key, rather than a seed, a
pairwise consistency test (PCT) is optionally performed. By default, or when this parameter is set
explicitly to "random", the PCT is performed with a random entropy value for the encapsulation step.
Setting the parameter to "fixed", still runs the test, but the encapsulation entropy is a fixed 32
byte value. Specifying any other value of the parameter, e.g. "none", skips the test.
"ml-kem.retain_seed" (OSSL_PKEY_PARAM_ML_KEM_RETAIN_SEED) <UTF8 string>
When set to a string representing a false boolean value (see OSSL_PROVIDER_conf_get_bool(3)), the
seed will not be retained after key generation or key import from a seed value. If the resulting key
is then written to a PKCS#8 object, it will contain only the FIPS 203 "dk" key.
"ml-kem.prefer_seed" (OSSL_PKEY_PARAM_ML_KEM_PREFER_SEED) <UTF8 string>
When decoding PKCS#8 objects that contain both a seed and the FIPS 203 "dk" private key, the seed is
by default used to regenerate the key, and the companion key is ignored. When this configuration
parameter is set to a string representing a false boolean value (see OSSL_PROVIDER_conf_get_bool(3)),
the seed is ignored (neither used to regenerate the key, nor retained), and the companion key is used
instead.
"ml-kem.input_formats" (OSSL_PKEY_PARAM_ML_KEM_INPUT_FORMATS) <UTF8 string>
List of enabled private key input formats when parsing PKCS#8 objects. List elements are separated
by commas and/or spaces or tabs. The list of enabled formats can be specified in the configuration
file, as seen in the "EXAMPLES" section below, or the via the -provparam command-line option (see
also OSSL_PROVIDER_add_conf_parameter(3)).
Values specified on the command-line override any configuration file settings. By default all the
supported formats are enabled. The supported formats are:
"seed-priv":
This format represents PKCS#8 objects in which both the FIPS 203 64-byte (d, z) seed and the
decapsulation key dk are present in the private key as part of the DER encoding of the ASN.1
sequence:
ML-KEM-PrivateKey ::= CHOICE {
seed [0] IMPLICIT OCTET STRING (SIZE (64)),
expandedKey OCTET STRING (SIZE (1632 | 2400 | 3168)),
both SEQUENCE {
seed OCTET STRING (SIZE (64)),
expandedKey OCTET STRING (SIZE (1632 | 2400 | 3168)) } }
If the "seed-priv" format is not included in the list, this format will not be recognised on
input.
"seed-only":
This format represents PKCS#8 objects in which only the 64-byte (d, z) seed is present in the
above sequence. If the "seed-only" format is not included in the list, this format will not be
recognised on input.
"priv-only":
This format represents PKCS#8 objects in which only the FIPS 203 decapsulation key dk is present
in the above sequence. If the "priv-only" format is not included in the list, this format will
not be recognised on input.
"oqskeypair":
This format represents PKCS#8 objects in which the private key is a DER encoding of an octet
string containing the concatenaton of the FIPS 203 decapsulation key dk and the encapsulation key
ek. This encoding is used in some builds of the "oqsprovider". If the "oqskeypair" format is
not included in the list, this format will not be recognised on input.
"bare-seed":
This format represents PKCS#8 objects in which the private key contains the 64-byte FIPS 204 seed
(d, z) without any ASN.1 encapsulation. If the "bare-seed" format is not included in the list,
this format will not be recognised on input.
"bare-priv":
This format represents PKCS#8 objects in which the private key contains the FIPS 204
decapsulation key dk without any ASN.1 encapsulation. If the "bare-priv" format is not included
in the list, this format will not be recognised on input.
"ml-kem.output_formats" (OSSL_PKEY_PARAM_ML_KEM_OUTPUT_FORMATS) <UTF8 string>
Ordered list of enabled private key output formats when writing PKCS#8 files. List elements are
separated by commas, spaces or tabs. The list of enabled formats can be specified in the
configuration file, as seen in the "EXAMPLES" section below, or the via the -provparam command-line
option.
This supports the same set of formats as described under "ml-kem.input_formats" above. The order in
which elements are listed is important, the selected format will be the first one that is possible to
output. If the key seed is known, the first listed format will be selected. If the key seed is not
known, the first format that omits the seed will be selected. The default order is equivalent to
"seed-priv" first and "priv-only" second, with both seed and key output when the seed is available,
and just the key otherwise. If "seed-only" is listed first, then the seed will be output without the
key when available, otherwise the output will have just the key. If "priv-only" is listed first,
then just the key is output regardless of whether the seed is present. The legacy "oqskeypair",
"bare-seed" and "bare-priv" formats can also be output, by listing those first.
CONFORMING TO
FIPS 203
EXAMPLES
An EVP_PKEY context can be obtained by calling:
EVP_PKEY_CTX *pctx =
EVP_PKEY_CTX_new_from_name(NULL, "ML-KEM-768", NULL);
An ML-KEM-768 key can be generated like this:
pkey = EVP_PKEY_Q_keygen(NULL, NULL, "ML-KEM-768");
An ML-KEM private key in seed format can be converted to a key in the FIPS 203 dk format by running:
$ openssl pkey -provparam ml-kem.retain_seed=no \
-in seed-only.pem -out priv-only.pem
To generate an, e.g., ML-KEM-768 key, in FIPS 203 dk format, you can run:
$ openssl genpkey -provparam ml-kem.retain_seed=no \
-algorithm ml-kem-768 -out priv-only.pem
If you have a PKCS#8 file with both a seed and a key, and prefer to import the companion key rather than
the seed, you can run:
$ openssl pkey -provparam ml-kem.prefer_seed=no \
-in seed-priv.pem -out priv-only.pem
In the openssl.cnf file, this looks like:
openssl_conf = openssl_init
[openssl_init]
providers = providers_sect
# Can be referenced in one or more provider sections
[ml_kem_sect]
prefer_seed = yes
retain_seed = yes
# OQS legacy formats disabled
input_formats = seed-priv, seed-only, priv-only
# Output either the seed alone, or else the key alone
output_formats = seed-only, priv-only
[providers_sect]
default = default_sect
# Or perhaps just: base = default_sect
base = base_sect
[default_sect]
ml-kem = ml_kem_sect
[base_sect]
ml-kem = ml_kem_sect
SEE ALSO
openssl(1), openssl-pkey(1), openssl-genpkey(1), EVP_KEYMGMT(3), EVP_PKEY(3),
EVP_PKEY_get_raw_private_key(3), EVP_PKEY_get_raw_public_key(3), EVP_PKEY_get1_encoded_public_key(3),
OSSL_PROVIDER_add_conf_parameter(3), provider-keymgmt(7), EVP_KEM-ML-KEM(7)
HISTORY
This functionality was added in OpenSSL 3.5.
COPYRIGHT
Copyright 2024-2025 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance
with the License. You can obtain a copy in the file LICENSE in the source distribution or at
<https://www.openssl.org/source/license.html>.
3.5.0 2025-06-04 EVP_PKEY-ML-KEM(7SSL)