EVP_SIGNATURE-LMS

- NAME
- DESCRIPTION
- NOTES
- EXAMPLES
  - LMS signature verification
- SEE ALSO
- HISTORY
- COPYRIGHT

# NAME

EVP_SIGNATURE-LMS - The EVP_PKEY LMS signature implementation

# DESCRIPTION

The LMS EVP_PKEY implementation supports Leighton-Micali Signatures (LMS) described in [RFC 8554](https://datatracker.ietf.org/doc/html/rfc8854) and [SP 800-208](https://csrc.nist.gov/pubs/sp/800/208/final). The OpenSSL providers only support LMS signature verification, as this is a [SP 800-208](https://csrc.nist.gov/pubs/sp/800/208/final) requirement for FIPS software modules.

EVP_PKEY_verify_message_init() and EVP_PKEY_verify() are the only supported functions used for LMS signatures. Streaming is not currently supported, and since the signature data contains data related to the digest used, functions that specify the digest name are not necessary.

# NOTES

LMS support is disabled by default at compile-time. To enable, specify the enable-lms build configuration option.

LMS should only be used for older deployments. New deployments should use either EVP_SIGNATURE-ML-DSA(7) or <L/EVP_SIGNATURE-SLH-DSA(7)>.

# EXAMPLES

Error checking has been omitted from the following examples

## LMS signature verification

    /* See L<EVP_PKEY-LMS(7)/EXAMPLES for an example of loading a LMS |pub| key */
    ctx = EVP_PKEY_CTX_new_from_pkey(libctx, pub, propq);
    sig = EVP_SIGNATURE_fetch(libctx, "LMS", propq);
    EVP_PKEY_verify_message_init(ctx, sig, NULL);
    /*
     * EVP_PKEY_verify_message_update() and EVP_PKEY_verify_message_final()
     * are not supported
     */
    ret = EVP_PKEY_verify(ctx, sigdata, sigdata_len, msg, msglen);
    /*
     * ret == 1 indicates success, 0 verify failure and < 0 for some
     * other error.
     */

# SEE ALSO

EVP_PKEY-LMS(7), provider-signature(7),

# HISTORY

This functionality was added in OpenSSL 3.6.

# COPYRIGHT

Copyright 2025-2026 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.