evp_pkey-ml-dsa(7ssl)

NAME#

EVP_PKEY-ML-DSA, EVP_KEYMGMT-ML-DSA, EVP_PKEY-ML-DSA-44, EVP_PKEY-ML-DSA-65, EVP_PKEY-ML-DSA-87 - EVP_PKEY ML-DSA keytype and algorithm support

DESCRIPTION#

ML-DSA implements the algorithms ML-DSA-44, ML-DSA-65 and ML-DSA-87. The key types EVP_PKEY_ML_DSA_44, EVP_PKEY_ML_DSA_65 and EVP_PKEY_ML_DSA_87 are implemented in OpenSSL's default and FIPS providers. These implementations support the associated key, containing the public key pub and the private key priv.

Each of the different key types has an associated security category. This value is one of 2, 3 or 5 for key types ML-DSA-44, ML-DSA-65 and ML-DSA-87 respectively, which correspond to security strengths of 128, 192 and 256 respectively.

Keygen Parameters#

"seed" (OSSL_PKEY_PARAM_ML_DSA_SEED) <octet string>

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 204 "sk" format.

"properties" (OSSL_PKEY_PARAM_PROPERTIES) <UTF8 string>

Sets properties to be used when fetching algorithm implementations used for ML-DSA hashing operations.

Use EVP_PKEY_CTX_set_params(3) after calling EVP_PKEY_keygen_init(3).

Common ML-DSA parameters#

In addition to the common parameters that all keytypes should support (see "Common Information Parameters" in provider-keymgmt(7), the implementation of these key types 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 encoded public key value of size 1312, 1952 or 2592 bytes depending on the respective key type of ML-DSA-44, ML-DSA-65 or ML-DSA-87.

"priv" (OSSL_PKEY_PARAM_PRIV_KEY) <octet string>

The encoded private key value of size 2560, 4032 or 4896 bytes depending on the respective key type of ML-DSA-44, ML-DSA-65 or ML-DSA-87.

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-dsa.retain_seed" (OSSL_PKEY_PARAM_ML_DSA_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 204 "sk" key.

"ml-dsa.prefer_seed" (OSSL_PKEY_PARAM_ML_DSA_PREFER_SEED) <UTF8 string>

When decoding PKCS#8 objects that contain both a seed and the FIPS 204 "sk" private key, the seed is by default used to regenerate the key, and the companion private 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-dsa.input_formats" (OSSL_PKEY_PARAM_ML_DSA_INPUT_FORMATS) <UTF8 string>

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":

bash

    ML-DSA-PrivateKey ::= CHOICE {
      seed [0] IMPLICIT OCTET STRING (SIZE (32)),
      expandedKey OCTET STRING (SIZE (2560 | 4032 | 4896)),
      both SEQUENCE {
        seed OCTET STRING (SIZE (32)),
        expandedKey OCTET STRING (SIZE (2560 | 4032 | 4896)) } }

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 32-byte FIPS 204 ξ 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 204 private key sk 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 204 private key sk and the public key pk. 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 32-byte FIPS 204 seed ξ 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 secret key sk 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-dsa.output_formats" (OSSL_PKEY_PARAM_ML_DSA_OUTPUT_FORMATS) <UTF8 string>

This supports the same set of formats as described under "ml-dsa.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 204

EXAMPLES#

An EVP_PKEY context can be obtained by calling:

    EVP_PKEY_CTX *pctx =
        EVP_PKEY_CTX_new_from_name(NULL, "ML-DSA-44", NULL);

An ML-DSA-44 key can be generated like this:

    pkey = EVP_PKEY_Q_keygen(NULL, NULL, "ML-DSA-44");

The key pair components can be extracted from a key by calling:

    /* Sizes large enough for ML-DSA-87 */
    uint8_t pub[2592], priv[4896], seed[32]:
    size_t priv_len, pub_len, seed_len;
    EVP_PKEY_get_octet_string_param(pkey, OSSL_PKEY_PARAM_ML_DSA_SEED,
                                    seed, sizeof(seed), &seed_len);
    EVP_PKEY_get_octet_string_param(pkey, OSSL_PKEY_PARAM_PRIV_KEY,
                                    priv, sizeof(priv), &priv_len);
    EVP_PKEY_get_octet_string_param(pkey, OSSL_PKEY_PARAM_PUB_KEY,
                                    pub, sizeof(pub), &pub_len));

An ML-DSA private key in seed format can be converted to a key in the FIPS 204 sk format by running:

    $ openssl pkey -provparam ml-dsa.retain_seed=no \
        -in seed-only.pem -out priv-only.pem

To generate an, e.g., ML-DSA-65 key, in FIPS 204 sk format, you can run:

    $ openssl genpkey -provparam ml-dsa.retain_seed=no \
        -algorithm ml-dsa-65 -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-dsa.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_dsa_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-dsa = ml_dsa_sect
    [base_sect]
    ml-dsa = ml_dsa_sect

SEE ALSO#

EVP_KEYMGMT(3), EVP_PKEY(3), provider-keymgmt(7), 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_SIGNATURE-ML-DSA(7)

HISTORY#

This functionality was added in OpenSSL 3.5.

COPYRIGHT#

Copyright 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>.