NAME

       EVP_PKEY-SLH-DSA, EVP_KEYMGMT-SLH-DSA, EVP_PKEY-SLH-DSA-SHA2-128s, EVP_PKEY-SLH-DSA-SHA2-128f,
       EVP_PKEY-SLH-DSA-SHA2-192s, EVP_PKEY-SLH-DSA-SHA2-192f, EVP_PKEY-SLH-DSA-SHA2-256s,
       EVP_PKEY-SLH-DSA-SHA2-256f, EVP_PKEY-SLH-DSA-SHAKE-128s, EVP_PKEY-SLH-DSA-SHAKE-128f,
       EVP_PKEY-SLH-DSA-SHAKE-192s, EVP_PKEY-SLH-DSA-SHAKE-192f, EVP_PKEY-SLH-DSA-SHAKE-256s,
       EVP_PKEY-SLH-DSA-SHAKE-256f - EVP_PKEY SLH-DSA keytype and algorithm support

DESCRIPTION

       The SLH-DSA-SHA2-128s, EVP_PKEY-SLH-DSA-SHA2-128f, SLH-DSA-SHA2-192s, EVP_PKEY-SLH-DSA-SHA2-192f,
       SLH-DSA-SHA2-256s, EVP_PKEY-SLH-DSA-SHA2-256f, SLH-DSA-SHAKE-128s, EVP_PKEY-SLH-DSA-SHAKE-128f,
       SLH-DSA-SHAKE-192s, EVP_PKEY-SLH-DSA-SHAKE-192f, SLH-DSA-SHAKE-256s and EVP_PKEY-SLH-DSA-SHAKE-256f key
       types 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.

       SLH-DSA (Stateless Hash-based Digital Signature Standard) uses small keys, but has relatively large
       signatures and is relatively slow performing all operations compared to ML-DSA. It does however have
       proven security proofs, since it relies only on hash functions.

       Each of the different key types has an associated security parameter n.  This value is one of 16, 24 or
       32 for key types SLH-DSA*128*, SLH-DSA*192* and SLH-DSA*256*, respectively.

       Both the public and private key components contain 2 elements of size n.  Key generation generates the
       private key elements and one of the public key elements randomly, and the final public key element is
       computed from these values.

       The public key has relatively small sizes of 32, 48 or 64 bytes, corresponding to the algorithm names of
       128, 192 and 256 respectively.

       The algorithms ending with s produce smaller signatures, but are much slower than the faster f variants.

       The signature sizes for the s algorithm variants are 7856, 16224 and 29792 which correspond to the
       algorithm names of 128s, 192s and 256s respectively.  The signature sizes for the f algorithm variants
       are 17088, 35664 and 49856 which correspond to the algorithm names containing 128f, 192f and 256f
       respectively.

       Internally there are 7 hash related functions that are used for each algorithm.  For algorithms
       containing SHAKE in their name SHAKE-256 is used for all functions.  For the <SHA2-128> algorithms the
       functions use <MGF1-SHA-256>, <HMAC-SHA-256> and <SHA-256>.  The remaining <SHA2> algorithms use
       <MGF1-SHA-512>, <HMAC-SHA-512>, <SHA-256> and <SHA-512>.  See FIPS 205 Section 11.1 and 11.2 for more
       information.

   Keygen Parameters
       "seed" (OSSL_PKEY_PARAM_SLH_DSA_SEED) <octet string>
           Supplies values to use for the private seed, private prf and public seed instead of generating random
           values. This is used for testing purposes only. The length of the value supplied must be 3 * n.

       "properties" (OSSL_PKEY_PARAM_PROPERTIES) <utf8_string>
           Sets  properties  to  be  used  when  fetching  algorithm  implementations  used  for SLH-DSA hashing
           operations.

       Use EVP_PKEY_CTX_set_params() after calling EVP_PKEY_keygen_init().

   Common SLH-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 following.

       The  following  parameters  are gettable using EVP_PKEY_get_octet_string_param(), and settable when using
       EVP_PKEY_fromdata().

       "pub" (OSSL_PKEY_PARAM_PUB_KEY) <octet string>
           The public key has a size of 2 * n bytes.  i.e. It consists  of  the  concatenation  of  PK.seed  and
           PK.root as defined by FIPS 205 Figure 16.

       "priv" (OSSL_PKEY_PARAM_PRIV_KEY) <octet string>
           The  private  key  has  a  size  of  4  * n bytes, which includes the public key components.  i.e. It
           consists of the concatenation of SK.seed, SK.prf, PK.seed and PF.root as defined by FIPS  205  Figure
           15.

       "mandatory-digest" (OSSL_PKEY_PARAM_MANDATORY_DIGEST) <UTF8 string>
           The empty string, signifying that no digest may be specified.

CONFORMING TO

       FIPS 205

EXAMPLES

       An EVP_PKEY context can be obtained by calling:

           EVP_PKEY_CTX *pctx =
               EVP_PKEY_CTX_new_from_name(NULL, "SLH-DSA-SHA2-128f", NULL);

       An SLH-DSA key can be generated like this:

           pkey = EVP_PKEY_Q_keygen(NULL, NULL, "SLH-DSA-SHA2-128f");

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

           uint8_t priv[64], pub[32];
           size_t priv_len, pub_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));

       Similar code can be used for the other key types such as "SLH-DSA-SHAKE-256f".

SEE ALSO

       EVP_KEYMGMT(3), EVP_PKEY(3), provider-keymgmt(7), EVP_SIGNATURE-SLH-DSA(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-SLH-DSA(7SSL)