library/lmots.c - mirror/mbed-tls.git - TrustedFirmware Git Browser

 /*
  * The LM-OTS one-time public-key signature scheme
  *
  * Copyright The Mbed TLS Contributors
  *  SPDX-License-Identifier: Apache-2.0
  *
  *  Licensed under the Apache License, Version 2.0 (the "License"); you may
  *  not use this file except in compliance with the License.
  *  You may obtain a copy of the License at
  *
  *  http://www.apache.org/licenses/LICENSE-2.0
  *
  *  Unless required by applicable law or agreed to in writing, software
  *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  *  See the License for the specific language governing permissions and
  *  limitations under the License.
  */

 /*
  *  The following sources were referenced in the design of this implementation
  *  of the LM-OTS algorithm:
  *
  *  [1] IETF RFC8554
  *      D. McGrew, M. Curcio, S.Fluhrer
  *      https://datatracker.ietf.org/doc/html/rfc8554
  *
  *  [2] NIST Special Publication 800-208
  *      David A. Cooper et. al.
  *      https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-208.pdf
  */

 #include "common.h"

 #ifdef MBEDTLS_LMOTS_C

 #include <string.h>

 #include "mbedtls/lmots.h"
 #include "mbedtls/md.h"
 #include "mbedtls/platform_util.h"
 #include "mbedtls/error.h"

 #define W_SYMBOL_BIT_LEN      (8)
 #define CHECKSUM_LEN          (2)
 #define I_SYMBOL_IDX_LEN      (2)
 #define J_HASH_IDX_LEN        (1)
 #define D_CONST_LEN           (2)

 #define SYMBOL_MAX_VAL        ((1 << W_SYMBOL_BIT_LEN) - 1)

 #define D_PBLC_CONSTANT       (0x8080)
 #define D_MESG_CONSTANT       (0x8181)

 static void val_to_network_bytes(unsigned int val, size_t len, unsigned char *bytes)
 {
     size_t idx;

     for (idx = 0; idx < len; idx++) {
         bytes[idx] = (val >> ((len - 1 - idx) * 8)) & 0xFF;
     }
 }

 static unsigned int network_bytes_to_val(size_t len, const unsigned char *bytes)
 {
     size_t idx;
     unsigned int val = 0;

     for (idx = 0; idx < len; idx++) {
         val |= ((unsigned int)bytes[idx]) << (8 * (len - 1 - idx));
     }

     return val;
 }

 static unsigned short lmots_checksum_generate( const unsigned char* digest )
 {
     size_t idx;
     unsigned short sum = 0;

     for ( idx = 0; idx < MBEDTLS_LMOTS_N_HASH_LEN; idx++ )
     {
         sum += ( 1 << W_SYMBOL_BIT_LEN ) - 1 - digest[idx];
     }

     return sum;
 }

 static int create_symbol_array( const unsigned char I_key_identifier[MBEDTLS_LMOTS_I_KEY_ID_LEN],
                                 const unsigned char q_leaf_identifier[MBEDTLS_LMOTS_Q_LEAF_ID_LEN],
                                 const unsigned char *msg,
                                 size_t msg_len,
                                 const unsigned char C_random_value[MBEDTLS_LMOTS_C_RANDOM_VALUE_LEN],
                                 unsigned char out[MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN] )
 {
     mbedtls_md_context_t hash_ctx;
     unsigned char D_MESG_BYTES[D_CONST_LEN];
     unsigned short checksum;
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

     mbedtls_md_init( &hash_ctx );
     ret = mbedtls_md_setup( &hash_ctx, mbedtls_md_info_from_type( MBEDTLS_MD_SHA256 ), 0 );
     if( ret )
     {
         goto out;
     }
     ret = mbedtls_md_starts( &hash_ctx );
     if ( ret )
     {
         goto out;
     }

     ret = mbedtls_md_update( &hash_ctx, I_key_identifier, MBEDTLS_LMOTS_I_KEY_ID_LEN );
     if ( ret )
     {
         goto out;
     }

     ret = mbedtls_md_update( &hash_ctx, q_leaf_identifier, MBEDTLS_LMOTS_Q_LEAF_ID_LEN );
     if ( ret )
     {
         goto out;
     }

     val_to_network_bytes( D_MESG_CONSTANT, D_CONST_LEN, D_MESG_BYTES );
     ret = mbedtls_md_update( &hash_ctx, D_MESG_BYTES, sizeof( D_MESG_BYTES ) );
     if ( ret )
     {
         goto out;
     }

     ret = mbedtls_md_update( &hash_ctx, C_random_value, MBEDTLS_LMOTS_C_RANDOM_VALUE_LEN );
     if ( ret )
     {
         goto out;
     }

     ret = mbedtls_md_update( &hash_ctx, msg, msg_len );
     if ( ret )
     {
         goto out;
     }

     ret = mbedtls_md_finish( &hash_ctx, out );
     if ( ret )
     {
         goto out;
     }

     checksum = lmots_checksum_generate( out );
     val_to_network_bytes( checksum, CHECKSUM_LEN, out + MBEDTLS_LMOTS_N_HASH_LEN );

 out:
     mbedtls_md_free( &hash_ctx );

     return( ret );
 }

 static int hash_symbol_array( const unsigned char I_key_identifier[MBEDTLS_LMOTS_I_KEY_ID_LEN],
                               const unsigned char q_leaf_identifier[MBEDTLS_LMOTS_Q_LEAF_ID_LEN],
                               const unsigned char x_symbol_array[MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN][32],
                               const unsigned char hash_idx_min_values[MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN],
                               const unsigned char hash_idx_max_values[MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN],
                               unsigned char output[MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN][32] )
 {
     unsigned char i_symbol_idx;
     unsigned char j_hash_idx;
     unsigned char i_symbol_idx_bytes[I_SYMBOL_IDX_LEN];
     unsigned char j_hash_idx_bytes[1];
     unsigned short j_hash_idx_min;
     unsigned short j_hash_idx_max;
     mbedtls_md_context_t hash_ctx;
     unsigned char tmp_hash[32];
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

     for ( i_symbol_idx = 0; i_symbol_idx < MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN; i_symbol_idx++ )
     {

         memcpy( tmp_hash, &x_symbol_array[i_symbol_idx], MBEDTLS_LMOTS_N_HASH_LEN );

         j_hash_idx_min = hash_idx_min_values != NULL ? hash_idx_min_values[i_symbol_idx] : 0;
         j_hash_idx_max = hash_idx_max_values != NULL ? hash_idx_max_values[i_symbol_idx] : SYMBOL_MAX_VAL;

         for ( j_hash_idx = (unsigned char)j_hash_idx_min; j_hash_idx < j_hash_idx_max; j_hash_idx++ )
         {
             mbedtls_md_init( &hash_ctx );
             ret = mbedtls_md_setup( &hash_ctx, mbedtls_md_info_from_type( MBEDTLS_MD_SHA256 ), 0 );
             if( ret )
             {
                 goto out;
             }
             ret = mbedtls_md_starts( &hash_ctx );
             if ( ret )
             {
                 goto out;
             }

             ret = mbedtls_md_update( &hash_ctx, I_key_identifier, MBEDTLS_LMOTS_I_KEY_ID_LEN );
             if ( ret )
             {
                 goto out;
             }

             ret = mbedtls_md_update( &hash_ctx, q_leaf_identifier, MBEDTLS_LMOTS_Q_LEAF_ID_LEN );
             if ( ret )
             {
                 goto out;
             }

             val_to_network_bytes( i_symbol_idx, I_SYMBOL_IDX_LEN, i_symbol_idx_bytes );
             ret = mbedtls_md_update( &hash_ctx, i_symbol_idx_bytes, I_SYMBOL_IDX_LEN );
             if ( ret )
             {
                 goto out;
             }

             val_to_network_bytes( j_hash_idx, J_HASH_IDX_LEN, j_hash_idx_bytes );
             ret = mbedtls_md_update( &hash_ctx, j_hash_idx_bytes, J_HASH_IDX_LEN );
             if ( ret )
             {
                 goto out;
             }

             ret = mbedtls_md_update( &hash_ctx, tmp_hash, MBEDTLS_LMOTS_N_HASH_LEN );
             if ( ret )
             {
                 goto out;
             }

             ret = mbedtls_md_finish( &hash_ctx, tmp_hash );
             if ( ret )
             {
                 goto out;
             }

             mbedtls_md_free( &hash_ctx );
         }

         memcpy( &output[i_symbol_idx], tmp_hash, MBEDTLS_LMOTS_N_HASH_LEN );
     }

 out:
     if( ret )
     {
         mbedtls_md_free( &hash_ctx );
         return( ret );
     }

     return ret;
 }

 static int public_key_from_hashed_symbol_array( const unsigned char I_key_identifier[MBEDTLS_LMOTS_I_KEY_ID_LEN],
                                                 const unsigned char q_leaf_identifier[MBEDTLS_LMOTS_Q_LEAF_ID_LEN],
                                                 const unsigned char  y_hashed_symbols[MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN][32],
                                                 unsigned char *pub_key )
 {
     unsigned char D_PBLC_bytes[D_CONST_LEN];
     mbedtls_md_context_t hash_ctx;
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

     mbedtls_md_init( &hash_ctx );
     ret = mbedtls_md_setup( &hash_ctx, mbedtls_md_info_from_type( MBEDTLS_MD_SHA256 ), 0 );
     if( ret )
     {
         goto out;
     }
     ret = mbedtls_md_starts( &hash_ctx );
     if ( ret )
     {
         goto out;
     }

     ret = mbedtls_md_update( &hash_ctx, I_key_identifier,
                              MBEDTLS_LMOTS_I_KEY_ID_LEN );
     if ( ret )
     {
         goto out;
     }

     ret = mbedtls_md_update( &hash_ctx, q_leaf_identifier,
                              MBEDTLS_LMOTS_Q_LEAF_ID_LEN );
     if ( ret )
     {
         goto out;
     }

     val_to_network_bytes( D_PBLC_CONSTANT, D_CONST_LEN, D_PBLC_bytes );
     ret = mbedtls_md_update( &hash_ctx, D_PBLC_bytes, D_CONST_LEN );
     if ( ret )
     {
         goto out;
     }

     ret = mbedtls_md_update( &hash_ctx, ( unsigned char * )y_hashed_symbols,
                              MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN * MBEDTLS_LMOTS_N_HASH_LEN );
     if ( ret )
     {
         goto out;
     }

     ret = mbedtls_md_finish( &hash_ctx, pub_key );

 out:
     mbedtls_md_free( &hash_ctx );
     return( ret );
 }

 void mbedtls_lmots_init( mbedtls_lmots_context *ctx )
 {
     if( ctx == NULL ) {
         return;
     }

     mbedtls_platform_zeroize( ctx, sizeof( mbedtls_lmots_context  ) ) ;
 }

 void mbedtls_lmots_free( mbedtls_lmots_context *ctx )
 {
     if( ctx == NULL )
     {
         return;
     }

     mbedtls_platform_zeroize( ctx, sizeof( mbedtls_lmots_context  ) ) ;
 }

 int mbedtls_lmots_set_algorithm_type( mbedtls_lmots_context *ctx,
                                       mbedtls_lmots_algorithm_type_t type )
 {
     if( ctx == NULL )
     {
         return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
     }

     ctx->MBEDTLS_PRIVATE(type) = type;

     return( 0 );
 }

 int mbedtls_lmots_generate_pub_key_candidate( const unsigned char I_key_identifier[MBEDTLS_LMOTS_I_KEY_ID_LEN],
                                               const unsigned char q_leaf_identifier[MBEDTLS_LMOTS_Q_LEAF_ID_LEN],
                                               const unsigned char  *msg,
                                               size_t msg_len,
                                               const unsigned char *sig,
                                               unsigned char *out )
 {
     unsigned char tmp_symbol_array[MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN];
     unsigned char y_hashed_symbols[MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN][32];
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

     if (I_key_identifier == NULL || msg == NULL || sig == NULL || out == NULL)
     {
         return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
     }

     ret = create_symbol_array( I_key_identifier, q_leaf_identifier, msg, msg_len,
                                sig + MBEDTLS_LMOTS_SIG_C_RANDOM_OFFSET, tmp_symbol_array );
     if ( ret )
     {
         return ( ret );
     }

     ret = hash_symbol_array( I_key_identifier, q_leaf_identifier,
                              ( const unsigned char( *)[32] )(sig + MBEDTLS_LMOTS_SIG_SIGNATURE_OFFSET),
                              tmp_symbol_array, NULL, y_hashed_symbols );
     if ( ret )
     {
         return ( ret );
     }

     ret = public_key_from_hashed_symbol_array( I_key_identifier, q_leaf_identifier,
                                                ( const unsigned char( *)[32] )y_hashed_symbols,
                                                out );
     if ( ret )
     {
         return ( ret );
     }

     return( 0 );
 }

 int mbedtls_lmots_sign( mbedtls_lmots_context *ctx,
                         int (*f_rng)(void *, unsigned char *, size_t),
                         void *p_rng, const unsigned char *msg, size_t msg_len,
                         unsigned char *sig )
 {
     unsigned char tmp_symbol_array[MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN];
     unsigned char tmp_sig[MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN][MBEDTLS_LMOTS_N_HASH_LEN];
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

     if( ctx == NULL || f_rng == NULL || p_rng == NULL || msg == NULL || sig == NULL)
     {
         return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
     }

     /* Check that a private key is loaded */
     if ( !ctx->MBEDTLS_PRIVATE(have_privkey) )
     {
         return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
     }

     ret = f_rng( p_rng, sig + MBEDTLS_LMOTS_SIG_C_RANDOM_OFFSET, MBEDTLS_LMOTS_N_HASH_LEN );
     if ( ret )
     {
         return( ret );
     }

     ret = create_symbol_array( ctx->MBEDTLS_PRIVATE(I_key_identifier),
                                ctx->MBEDTLS_PRIVATE(q_leaf_identifier_bytes),
                                msg, msg_len, sig + MBEDTLS_LMOTS_SIG_C_RANDOM_OFFSET,
                                tmp_symbol_array );
     if ( ret )
     {
         return( ret );
     }

     ret = hash_symbol_array( ctx->MBEDTLS_PRIVATE(I_key_identifier),
                              ctx->MBEDTLS_PRIVATE(q_leaf_identifier_bytes),
                              ( const unsigned char( *)[32] )(ctx->MBEDTLS_PRIVATE(priv_key)),
                              NULL, tmp_symbol_array, tmp_sig );
     if ( ret )
     {
         return( ret );
     }

     val_to_network_bytes( ctx->MBEDTLS_PRIVATE(type), MBEDTLS_LMOTS_TYPE_LEN,
                           sig + MBEDTLS_LMOTS_SIG_TYPE_OFFSET );

     /* We've got a valid signature now, so it's time to make sure the private
      * key can't be reused.
      */
     ctx->MBEDTLS_PRIVATE(have_privkey) = 0;
     mbedtls_platform_zeroize(ctx->MBEDTLS_PRIVATE(priv_key),
                              sizeof(ctx->MBEDTLS_PRIVATE(priv_key)));

     memcpy(sig + MBEDTLS_LMOTS_SIG_SIGNATURE_OFFSET, tmp_sig,
            MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN * MBEDTLS_LMOTS_N_HASH_LEN);

     return( 0 );
 }

 int mbedtls_lmots_verify( mbedtls_lmots_context *ctx, const unsigned char *msg,
                           size_t msg_len, const unsigned char *sig )
 {
     unsigned char Kc_public_key_candidate[32];
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

     if( ctx == NULL || msg == NULL || sig == NULL)
     {
         return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
     }

     if ( !ctx->MBEDTLS_PRIVATE(have_pubkey) )
     {
         return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
     }

     if( ctx->MBEDTLS_PRIVATE(type ) != MBEDTLS_LMOTS_SHA256_N32_W8 )
     {
         return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
     }

     if ( network_bytes_to_val( MBEDTLS_LMOTS_TYPE_LEN,
                                sig + MBEDTLS_LMOTS_SIG_TYPE_OFFSET ) != MBEDTLS_LMOTS_SHA256_N32_W8 )
     {
         return( MBEDTLS_ERR_LMOTS_VERIFY_FAILED );
     }

     ret = mbedtls_lmots_generate_pub_key_candidate( ctx->MBEDTLS_PRIVATE(I_key_identifier),
                                                     ctx->MBEDTLS_PRIVATE(q_leaf_identifier_bytes),
                                                     msg, msg_len, sig,
                                                     Kc_public_key_candidate );
     if ( ret )
     {
         return( ret );
     }

     if ( memcmp( &Kc_public_key_candidate, ctx->MBEDTLS_PRIVATE(pub_key),
                  sizeof( ctx->MBEDTLS_PRIVATE(pub_key) ) ) )
     {
         return( MBEDTLS_ERR_LMOTS_VERIFY_FAILED );
     }

     return( 0 );
 }

 int mbedtls_lmots_import_pubkey( mbedtls_lmots_context *ctx,
                                  const unsigned char *key )
 {
     if ( ctx == NULL || key == NULL)
     {
         return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
     }

     ctx->MBEDTLS_PRIVATE(type) = network_bytes_to_val( MBEDTLS_LMOTS_TYPE_LEN,
                                                        key + MBEDTLS_LMOTS_SIG_TYPE_OFFSET );

     memcpy( ctx->MBEDTLS_PRIVATE(I_key_identifier), key + MBEDTLS_LMOTS_PUBKEY_I_KEY_ID_OFFSET,
             MBEDTLS_LMOTS_I_KEY_ID_LEN );

     memcpy( ctx->MBEDTLS_PRIVATE(q_leaf_identifier_bytes), key + MBEDTLS_LMOTS_PUBKEY_Q_LEAF_ID_OFFSET,
             MBEDTLS_LMOTS_Q_LEAF_ID_LEN );
     ctx->MBEDTLS_PRIVATE(q_leaf_identifier) = network_bytes_to_val( MBEDTLS_LMOTS_Q_LEAF_ID_LEN,
                                                                     ctx->MBEDTLS_PRIVATE(q_leaf_identifier_bytes) );

     memcpy( ctx->MBEDTLS_PRIVATE(pub_key), key + MBEDTLS_LMOTS_PUBKEY_KEY_HASH_OFFSET, MBEDTLS_LMOTS_N_HASH_LEN );

     ctx->MBEDTLS_PRIVATE(have_pubkey) = 1;

     return( 0 );
 }

 int mbedtls_lmots_export_pubkey( mbedtls_lmots_context *ctx,
                                  unsigned char *key )
 {
     if ( ctx == NULL || key == NULL)
     {
         return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
     }

     if ( ! ctx->MBEDTLS_PRIVATE(have_pubkey) )
     {
         return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
     }

     val_to_network_bytes( ctx->MBEDTLS_PRIVATE(type), MBEDTLS_LMOTS_TYPE_LEN,
                           key + MBEDTLS_LMOTS_SIG_TYPE_OFFSET );

     memcpy( key + MBEDTLS_LMOTS_PUBKEY_I_KEY_ID_OFFSET, ctx->MBEDTLS_PRIVATE(I_key_identifier),
             MBEDTLS_LMOTS_I_KEY_ID_LEN );

     memcpy( key + MBEDTLS_LMOTS_PUBKEY_Q_LEAF_ID_OFFSET, ctx->MBEDTLS_PRIVATE(q_leaf_identifier_bytes),
             MBEDTLS_LMOTS_Q_LEAF_ID_LEN );

     memcpy( key + MBEDTLS_LMOTS_PUBKEY_KEY_HASH_OFFSET, ctx->MBEDTLS_PRIVATE(pub_key),
             MBEDTLS_LMOTS_N_HASH_LEN );

     return( 0 );
 }


 int mbedtls_lmots_gen_pubkey( mbedtls_lmots_context *ctx )
 {
     unsigned char y_hashed_symbols[MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN][32];
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

     if( ctx == NULL )
     {
         return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
     }

     /* Check that a private key is loaded */
     if ( !ctx->MBEDTLS_PRIVATE(have_privkey) )
     {
         return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
     }

     ret = hash_symbol_array( ctx->MBEDTLS_PRIVATE(I_key_identifier),
                              ctx->MBEDTLS_PRIVATE(q_leaf_identifier_bytes),
                              ( const unsigned char( *)[32] )(ctx->MBEDTLS_PRIVATE(priv_key)),
                              NULL, NULL, y_hashed_symbols );
     if ( ret )
     {
         return( ret );
     }

     ret = public_key_from_hashed_symbol_array( ctx->MBEDTLS_PRIVATE(I_key_identifier),
                                                ctx->MBEDTLS_PRIVATE(q_leaf_identifier_bytes),
                                                ( const unsigned char( *)[32] )y_hashed_symbols,
                                                ctx->MBEDTLS_PRIVATE(pub_key) );
     if ( ret )
     {
         return( ret );
     }

     ctx->MBEDTLS_PRIVATE(have_pubkey = 1);

     return( ret );
 }

 int mbedtls_lmots_gen_privkey( mbedtls_lmots_context *ctx,
                                const unsigned char I_key_identifier[MBEDTLS_LMOTS_I_KEY_ID_LEN],
                                unsigned int q_leaf_identifier,
                                const unsigned char *seed,
                                size_t seed_len )
 {
     mbedtls_md_context_t hash_ctx;
     unsigned int i_symbol_idx;
     unsigned char i_symbol_idx_bytes[2];
     unsigned char const_bytes[1];
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

     if( ctx == NULL || I_key_identifier == NULL || seed == NULL)
     {
         return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
     }

     if ( ctx->MBEDTLS_PRIVATE(have_privkey) )
     {
         return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
     }

     if ( ctx->MBEDTLS_PRIVATE(type) != MBEDTLS_LMOTS_SHA256_N32_W8 ) {
         return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
     }

     memcpy( ctx->MBEDTLS_PRIVATE(I_key_identifier), I_key_identifier,
             sizeof( ctx->MBEDTLS_PRIVATE(I_key_identifier) ) );

     ctx->MBEDTLS_PRIVATE(q_leaf_identifier) = q_leaf_identifier;

     val_to_network_bytes( ctx->MBEDTLS_PRIVATE(q_leaf_identifier), MBEDTLS_LMOTS_Q_LEAF_ID_LEN,
                           ctx->MBEDTLS_PRIVATE(q_leaf_identifier_bytes) );

     val_to_network_bytes( 0xFF, sizeof( const_bytes ), const_bytes );

     for ( i_symbol_idx = 0; i_symbol_idx < MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN; i_symbol_idx++ )
     {
         mbedtls_md_init( &hash_ctx );
         ret = mbedtls_md_setup( &hash_ctx, mbedtls_md_info_from_type( MBEDTLS_MD_SHA256 ), 0 );
         if( ret )
         {
             goto out;
         }
         ret = mbedtls_md_starts( &hash_ctx );
         if ( ret )
         {
             goto out;
         }

         ret = mbedtls_md_update( &hash_ctx, ctx->MBEDTLS_PRIVATE(I_key_identifier),
                                  sizeof( ctx->MBEDTLS_PRIVATE(I_key_identifier) ) );
         if ( ret ) {
             goto out;
         }

         ret = mbedtls_md_update( &hash_ctx, ctx->MBEDTLS_PRIVATE(q_leaf_identifier_bytes),
                                  sizeof( ctx->MBEDTLS_PRIVATE(q_leaf_identifier_bytes) ) );
         if ( ret )
         {
             goto out;
         }

         val_to_network_bytes( i_symbol_idx, I_SYMBOL_IDX_LEN, i_symbol_idx_bytes );
         ret = mbedtls_md_update( &hash_ctx, i_symbol_idx_bytes, I_SYMBOL_IDX_LEN );
         if ( ret )
         {
             goto out;
         }

         ret = mbedtls_md_update( &hash_ctx, const_bytes, sizeof( const_bytes) );
         if ( ret )
         {
             goto out;
         }

         ret = mbedtls_md_update( &hash_ctx, seed, seed_len );
         if ( ret )
         {
             goto out;
         }

         ret = mbedtls_md_finish( &hash_ctx, ctx->MBEDTLS_PRIVATE(priv_key)[i_symbol_idx] );
         if ( ret )
         {
             goto out;
         }

         mbedtls_md_free( &hash_ctx);
     }

     ctx->MBEDTLS_PRIVATE(have_privkey) = 1;

 out:
     if( ret )
     {
         mbedtls_md_free( &hash_ctx );
         return( ret );
     }

     return ret;
 }

 #endif /* MBEDTLS_LMOTS_C */
	/*
	* The LM-OTS one-time public-key signature scheme
	*
	* Copyright The Mbed TLS Contributors
	* SPDX-License-Identifier: Apache-2.0
	*
	* Licensed under the Apache License, Version 2.0 (the "License"); you may
	* not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
	* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	/*
	* The following sources were referenced in the design of this implementation
	* of the LM-OTS algorithm:
	*
	* [1] IETF RFC8554
	* D. McGrew, M. Curcio, S.Fluhrer
	* https://datatracker.ietf.org/doc/html/rfc8554
	*
	* [2] NIST Special Publication 800-208
	* David A. Cooper et. al.
	* https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-208.pdf
	*/

	#include "common.h"

	#ifdef MBEDTLS_LMOTS_C

	#include <string.h>

	#include "mbedtls/lmots.h"
	#include "mbedtls/md.h"
	#include "mbedtls/platform_util.h"
	#include "mbedtls/error.h"

	#define W_SYMBOL_BIT_LEN (8)
	#define CHECKSUM_LEN (2)
	#define I_SYMBOL_IDX_LEN (2)
	#define J_HASH_IDX_LEN (1)
	#define D_CONST_LEN (2)

	#define SYMBOL_MAX_VAL ((1 << W_SYMBOL_BIT_LEN) - 1)

	#define D_PBLC_CONSTANT (0x8080)
	#define D_MESG_CONSTANT (0x8181)

	static void val_to_network_bytes(unsigned int val, size_t len, unsigned char *bytes)
	{
	size_t idx;

	for (idx = 0; idx < len; idx++) {
	bytes[idx] = (val >> ((len - 1 - idx) * 8)) & 0xFF;
	}
	}

	static unsigned int network_bytes_to_val(size_t len, const unsigned char *bytes)
	{
	size_t idx;
	unsigned int val = 0;

	for (idx = 0; idx < len; idx++) {
	val \|= ((unsigned int)bytes[idx]) << (8 * (len - 1 - idx));
	}

	return val;
	}

	static unsigned short lmots_checksum_generate( const unsigned char* digest )
	{
	size_t idx;
	unsigned short sum = 0;

	for ( idx = 0; idx < MBEDTLS_LMOTS_N_HASH_LEN; idx++ )
	{
	sum += ( 1 << W_SYMBOL_BIT_LEN ) - 1 - digest[idx];
	}

	return sum;
	}

	static int create_symbol_array( const unsigned char I_key_identifier[MBEDTLS_LMOTS_I_KEY_ID_LEN],
	const unsigned char q_leaf_identifier[MBEDTLS_LMOTS_Q_LEAF_ID_LEN],
	const unsigned char *msg,
	size_t msg_len,
	const unsigned char C_random_value[MBEDTLS_LMOTS_C_RANDOM_VALUE_LEN],
	unsigned char out[MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN] )
	{
	mbedtls_md_context_t hash_ctx;
	unsigned char D_MESG_BYTES[D_CONST_LEN];
	unsigned short checksum;
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

	mbedtls_md_init( &hash_ctx );
	ret = mbedtls_md_setup( &hash_ctx, mbedtls_md_info_from_type( MBEDTLS_MD_SHA256 ), 0 );
	if( ret )
	{
	goto out;
	}
	ret = mbedtls_md_starts( &hash_ctx );
	if ( ret )
	{
	goto out;
	}

	ret = mbedtls_md_update( &hash_ctx, I_key_identifier, MBEDTLS_LMOTS_I_KEY_ID_LEN );
	if ( ret )
	{
	goto out;
	}

	ret = mbedtls_md_update( &hash_ctx, q_leaf_identifier, MBEDTLS_LMOTS_Q_LEAF_ID_LEN );
	if ( ret )
	{
	goto out;
	}

	val_to_network_bytes( D_MESG_CONSTANT, D_CONST_LEN, D_MESG_BYTES );
	ret = mbedtls_md_update( &hash_ctx, D_MESG_BYTES, sizeof( D_MESG_BYTES ) );
	if ( ret )
	{
	goto out;
	}

	ret = mbedtls_md_update( &hash_ctx, C_random_value, MBEDTLS_LMOTS_C_RANDOM_VALUE_LEN );
	if ( ret )
	{
	goto out;
	}

	ret = mbedtls_md_update( &hash_ctx, msg, msg_len );
	if ( ret )
	{
	goto out;
	}

	ret = mbedtls_md_finish( &hash_ctx, out );
	if ( ret )
	{
	goto out;
	}

	checksum = lmots_checksum_generate( out );
	val_to_network_bytes( checksum, CHECKSUM_LEN, out + MBEDTLS_LMOTS_N_HASH_LEN );

	out:
	mbedtls_md_free( &hash_ctx );

	return( ret );
	}

	static int hash_symbol_array( const unsigned char I_key_identifier[MBEDTLS_LMOTS_I_KEY_ID_LEN],
	const unsigned char q_leaf_identifier[MBEDTLS_LMOTS_Q_LEAF_ID_LEN],
	const unsigned char x_symbol_array[MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN][32],
	const unsigned char hash_idx_min_values[MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN],
	const unsigned char hash_idx_max_values[MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN],
	unsigned char output[MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN][32] )
	{
	unsigned char i_symbol_idx;
	unsigned char j_hash_idx;
	unsigned char i_symbol_idx_bytes[I_SYMBOL_IDX_LEN];
	unsigned char j_hash_idx_bytes[1];
	unsigned short j_hash_idx_min;
	unsigned short j_hash_idx_max;
	mbedtls_md_context_t hash_ctx;
	unsigned char tmp_hash[32];
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

	for ( i_symbol_idx = 0; i_symbol_idx < MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN; i_symbol_idx++ )
	{

	memcpy( tmp_hash, &x_symbol_array[i_symbol_idx], MBEDTLS_LMOTS_N_HASH_LEN );

	j_hash_idx_min = hash_idx_min_values != NULL ? hash_idx_min_values[i_symbol_idx] : 0;
	j_hash_idx_max = hash_idx_max_values != NULL ? hash_idx_max_values[i_symbol_idx] : SYMBOL_MAX_VAL;

	for ( j_hash_idx = (unsigned char)j_hash_idx_min; j_hash_idx < j_hash_idx_max; j_hash_idx++ )
	{
	mbedtls_md_init( &hash_ctx );
	ret = mbedtls_md_setup( &hash_ctx, mbedtls_md_info_from_type( MBEDTLS_MD_SHA256 ), 0 );
	if( ret )
	{
	goto out;
	}
	ret = mbedtls_md_starts( &hash_ctx );
	if ( ret )
	{
	goto out;
	}

	ret = mbedtls_md_update( &hash_ctx, I_key_identifier, MBEDTLS_LMOTS_I_KEY_ID_LEN );
	if ( ret )
	{
	goto out;
	}

	ret = mbedtls_md_update( &hash_ctx, q_leaf_identifier, MBEDTLS_LMOTS_Q_LEAF_ID_LEN );
	if ( ret )
	{
	goto out;
	}

	val_to_network_bytes( i_symbol_idx, I_SYMBOL_IDX_LEN, i_symbol_idx_bytes );
	ret = mbedtls_md_update( &hash_ctx, i_symbol_idx_bytes, I_SYMBOL_IDX_LEN );
	if ( ret )
	{
	goto out;
	}

	val_to_network_bytes( j_hash_idx, J_HASH_IDX_LEN, j_hash_idx_bytes );
	ret = mbedtls_md_update( &hash_ctx, j_hash_idx_bytes, J_HASH_IDX_LEN );
	if ( ret )
	{
	goto out;
	}

	ret = mbedtls_md_update( &hash_ctx, tmp_hash, MBEDTLS_LMOTS_N_HASH_LEN );
	if ( ret )
	{
	goto out;
	}

	ret = mbedtls_md_finish( &hash_ctx, tmp_hash );
	if ( ret )
	{
	goto out;
	}

	mbedtls_md_free( &hash_ctx );
	}

	memcpy( &output[i_symbol_idx], tmp_hash, MBEDTLS_LMOTS_N_HASH_LEN );
	}

	out:
	if( ret )
	{
	mbedtls_md_free( &hash_ctx );
	return( ret );
	}

	return ret;
	}

	static int public_key_from_hashed_symbol_array( const unsigned char I_key_identifier[MBEDTLS_LMOTS_I_KEY_ID_LEN],
	const unsigned char q_leaf_identifier[MBEDTLS_LMOTS_Q_LEAF_ID_LEN],
	const unsigned char y_hashed_symbols[MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN][32],
	unsigned char *pub_key )
	{
	unsigned char D_PBLC_bytes[D_CONST_LEN];
	mbedtls_md_context_t hash_ctx;
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

	mbedtls_md_init( &hash_ctx );
	ret = mbedtls_md_setup( &hash_ctx, mbedtls_md_info_from_type( MBEDTLS_MD_SHA256 ), 0 );
	if( ret )
	{
	goto out;
	}
	ret = mbedtls_md_starts( &hash_ctx );
	if ( ret )
	{
	goto out;
	}

	ret = mbedtls_md_update( &hash_ctx, I_key_identifier,
	MBEDTLS_LMOTS_I_KEY_ID_LEN );
	if ( ret )
	{
	goto out;
	}

	ret = mbedtls_md_update( &hash_ctx, q_leaf_identifier,
	MBEDTLS_LMOTS_Q_LEAF_ID_LEN );
	if ( ret )
	{
	goto out;
	}

	val_to_network_bytes( D_PBLC_CONSTANT, D_CONST_LEN, D_PBLC_bytes );
	ret = mbedtls_md_update( &hash_ctx, D_PBLC_bytes, D_CONST_LEN );
	if ( ret )
	{
	goto out;
	}

	ret = mbedtls_md_update( &hash_ctx, ( unsigned char * )y_hashed_symbols,
	MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN * MBEDTLS_LMOTS_N_HASH_LEN );
	if ( ret )
	{
	goto out;
	}

	ret = mbedtls_md_finish( &hash_ctx, pub_key );

	out:
	mbedtls_md_free( &hash_ctx );
	return( ret );
	}

	void mbedtls_lmots_init( mbedtls_lmots_context *ctx )
	{
	if( ctx == NULL ) {
	return;
	}

	mbedtls_platform_zeroize( ctx, sizeof( mbedtls_lmots_context ) ) ;
	}

	void mbedtls_lmots_free( mbedtls_lmots_context *ctx )
	{
	if( ctx == NULL )
	{
	return;
	}

	mbedtls_platform_zeroize( ctx, sizeof( mbedtls_lmots_context ) ) ;
	}

	int mbedtls_lmots_set_algorithm_type( mbedtls_lmots_context *ctx,
	mbedtls_lmots_algorithm_type_t type )
	{
	if( ctx == NULL )
	{
	return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
	}

	ctx->MBEDTLS_PRIVATE(type) = type;

	return( 0 );
	}

	int mbedtls_lmots_generate_pub_key_candidate( const unsigned char I_key_identifier[MBEDTLS_LMOTS_I_KEY_ID_LEN],
	const unsigned char q_leaf_identifier[MBEDTLS_LMOTS_Q_LEAF_ID_LEN],
	const unsigned char *msg,
	size_t msg_len,
	const unsigned char *sig,
	unsigned char *out )
	{
	unsigned char tmp_symbol_array[MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN];
	unsigned char y_hashed_symbols[MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN][32];
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

	if (I_key_identifier == NULL \|\| msg == NULL \|\| sig == NULL \|\| out == NULL)
	{
	return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
	}

	ret = create_symbol_array( I_key_identifier, q_leaf_identifier, msg, msg_len,
	sig + MBEDTLS_LMOTS_SIG_C_RANDOM_OFFSET, tmp_symbol_array );
	if ( ret )
	{
	return ( ret );
	}

	ret = hash_symbol_array( I_key_identifier, q_leaf_identifier,
	( const unsigned char( *)[32] )(sig + MBEDTLS_LMOTS_SIG_SIGNATURE_OFFSET),
	tmp_symbol_array, NULL, y_hashed_symbols );
	if ( ret )
	{
	return ( ret );
	}

	ret = public_key_from_hashed_symbol_array( I_key_identifier, q_leaf_identifier,
	( const unsigned char( *)[32] )y_hashed_symbols,
	out );
	if ( ret )
	{
	return ( ret );
	}

	return( 0 );
	}

	int mbedtls_lmots_sign( mbedtls_lmots_context *ctx,
	int (f_rng)(void , unsigned char *, size_t),
	void p_rng, const unsigned char msg, size_t msg_len,
	unsigned char *sig )
	{
	unsigned char tmp_symbol_array[MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN];
	unsigned char tmp_sig[MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN][MBEDTLS_LMOTS_N_HASH_LEN];
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

	if( ctx == NULL \|\| f_rng == NULL \|\| p_rng == NULL \|\| msg == NULL \|\| sig == NULL)
	{
	return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
	}

	/* Check that a private key is loaded */
	if ( !ctx->MBEDTLS_PRIVATE(have_privkey) )
	{
	return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
	}

	ret = f_rng( p_rng, sig + MBEDTLS_LMOTS_SIG_C_RANDOM_OFFSET, MBEDTLS_LMOTS_N_HASH_LEN );
	if ( ret )
	{
	return( ret );
	}

	ret = create_symbol_array( ctx->MBEDTLS_PRIVATE(I_key_identifier),
	ctx->MBEDTLS_PRIVATE(q_leaf_identifier_bytes),
	msg, msg_len, sig + MBEDTLS_LMOTS_SIG_C_RANDOM_OFFSET,
	tmp_symbol_array );
	if ( ret )
	{
	return( ret );
	}

	ret = hash_symbol_array( ctx->MBEDTLS_PRIVATE(I_key_identifier),
	ctx->MBEDTLS_PRIVATE(q_leaf_identifier_bytes),
	( const unsigned char( *)[32] )(ctx->MBEDTLS_PRIVATE(priv_key)),
	NULL, tmp_symbol_array, tmp_sig );
	if ( ret )
	{
	return( ret );
	}

	val_to_network_bytes( ctx->MBEDTLS_PRIVATE(type), MBEDTLS_LMOTS_TYPE_LEN,
	sig + MBEDTLS_LMOTS_SIG_TYPE_OFFSET );

	/* We've got a valid signature now, so it's time to make sure the private
	* key can't be reused.
	*/
	ctx->MBEDTLS_PRIVATE(have_privkey) = 0;
	mbedtls_platform_zeroize(ctx->MBEDTLS_PRIVATE(priv_key),
	sizeof(ctx->MBEDTLS_PRIVATE(priv_key)));

	memcpy(sig + MBEDTLS_LMOTS_SIG_SIGNATURE_OFFSET, tmp_sig,
	MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN * MBEDTLS_LMOTS_N_HASH_LEN);

	return( 0 );
	}

	int mbedtls_lmots_verify( mbedtls_lmots_context ctx, const unsigned char msg,
	size_t msg_len, const unsigned char *sig )
	{
	unsigned char Kc_public_key_candidate[32];
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

	if( ctx == NULL \|\| msg == NULL \|\| sig == NULL)
	{
	return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
	}

	if ( !ctx->MBEDTLS_PRIVATE(have_pubkey) )
	{
	return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
	}

	if( ctx->MBEDTLS_PRIVATE(type ) != MBEDTLS_LMOTS_SHA256_N32_W8 )
	{
	return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
	}

	if ( network_bytes_to_val( MBEDTLS_LMOTS_TYPE_LEN,
	sig + MBEDTLS_LMOTS_SIG_TYPE_OFFSET ) != MBEDTLS_LMOTS_SHA256_N32_W8 )
	{
	return( MBEDTLS_ERR_LMOTS_VERIFY_FAILED );
	}

	ret = mbedtls_lmots_generate_pub_key_candidate( ctx->MBEDTLS_PRIVATE(I_key_identifier),
	ctx->MBEDTLS_PRIVATE(q_leaf_identifier_bytes),
	msg, msg_len, sig,
	Kc_public_key_candidate );
	if ( ret )
	{
	return( ret );
	}

	if ( memcmp( &Kc_public_key_candidate, ctx->MBEDTLS_PRIVATE(pub_key),
	sizeof( ctx->MBEDTLS_PRIVATE(pub_key) ) ) )
	{
	return( MBEDTLS_ERR_LMOTS_VERIFY_FAILED );
	}

	return( 0 );
	}

	int mbedtls_lmots_import_pubkey( mbedtls_lmots_context *ctx,
	const unsigned char *key )
	{
	if ( ctx == NULL \|\| key == NULL)
	{
	return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
	}

	ctx->MBEDTLS_PRIVATE(type) = network_bytes_to_val( MBEDTLS_LMOTS_TYPE_LEN,
	key + MBEDTLS_LMOTS_SIG_TYPE_OFFSET );

	memcpy( ctx->MBEDTLS_PRIVATE(I_key_identifier), key + MBEDTLS_LMOTS_PUBKEY_I_KEY_ID_OFFSET,
	MBEDTLS_LMOTS_I_KEY_ID_LEN );

	memcpy( ctx->MBEDTLS_PRIVATE(q_leaf_identifier_bytes), key + MBEDTLS_LMOTS_PUBKEY_Q_LEAF_ID_OFFSET,
	MBEDTLS_LMOTS_Q_LEAF_ID_LEN );
	ctx->MBEDTLS_PRIVATE(q_leaf_identifier) = network_bytes_to_val( MBEDTLS_LMOTS_Q_LEAF_ID_LEN,
	ctx->MBEDTLS_PRIVATE(q_leaf_identifier_bytes) );

	memcpy( ctx->MBEDTLS_PRIVATE(pub_key), key + MBEDTLS_LMOTS_PUBKEY_KEY_HASH_OFFSET, MBEDTLS_LMOTS_N_HASH_LEN );

	ctx->MBEDTLS_PRIVATE(have_pubkey) = 1;

	return( 0 );
	}

	int mbedtls_lmots_export_pubkey( mbedtls_lmots_context *ctx,
	unsigned char *key )
	{
	if ( ctx == NULL \|\| key == NULL)
	{
	return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
	}

	if ( ! ctx->MBEDTLS_PRIVATE(have_pubkey) )
	{
	return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
	}

	val_to_network_bytes( ctx->MBEDTLS_PRIVATE(type), MBEDTLS_LMOTS_TYPE_LEN,
	key + MBEDTLS_LMOTS_SIG_TYPE_OFFSET );

	memcpy( key + MBEDTLS_LMOTS_PUBKEY_I_KEY_ID_OFFSET, ctx->MBEDTLS_PRIVATE(I_key_identifier),
	MBEDTLS_LMOTS_I_KEY_ID_LEN );

	memcpy( key + MBEDTLS_LMOTS_PUBKEY_Q_LEAF_ID_OFFSET, ctx->MBEDTLS_PRIVATE(q_leaf_identifier_bytes),
	MBEDTLS_LMOTS_Q_LEAF_ID_LEN );

	memcpy( key + MBEDTLS_LMOTS_PUBKEY_KEY_HASH_OFFSET, ctx->MBEDTLS_PRIVATE(pub_key),
	MBEDTLS_LMOTS_N_HASH_LEN );

	return( 0 );
	}


	int mbedtls_lmots_gen_pubkey( mbedtls_lmots_context *ctx )
	{
	unsigned char y_hashed_symbols[MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN][32];
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

	if( ctx == NULL )
	{
	return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
	}

	/* Check that a private key is loaded */
	if ( !ctx->MBEDTLS_PRIVATE(have_privkey) )
	{
	return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
	}

	ret = hash_symbol_array( ctx->MBEDTLS_PRIVATE(I_key_identifier),
	ctx->MBEDTLS_PRIVATE(q_leaf_identifier_bytes),
	( const unsigned char( *)[32] )(ctx->MBEDTLS_PRIVATE(priv_key)),
	NULL, NULL, y_hashed_symbols );
	if ( ret )
	{
	return( ret );
	}

	ret = public_key_from_hashed_symbol_array( ctx->MBEDTLS_PRIVATE(I_key_identifier),
	ctx->MBEDTLS_PRIVATE(q_leaf_identifier_bytes),
	( const unsigned char( *)[32] )y_hashed_symbols,
	ctx->MBEDTLS_PRIVATE(pub_key) );
	if ( ret )
	{
	return( ret );
	}

	ctx->MBEDTLS_PRIVATE(have_pubkey = 1);

	return( ret );
	}

	int mbedtls_lmots_gen_privkey( mbedtls_lmots_context *ctx,
	const unsigned char I_key_identifier[MBEDTLS_LMOTS_I_KEY_ID_LEN],
	unsigned int q_leaf_identifier,
	const unsigned char *seed,
	size_t seed_len )
	{
	mbedtls_md_context_t hash_ctx;
	unsigned int i_symbol_idx;
	unsigned char i_symbol_idx_bytes[2];
	unsigned char const_bytes[1];
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

	if( ctx == NULL \|\| I_key_identifier == NULL \|\| seed == NULL)
	{
	return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
	}

	if ( ctx->MBEDTLS_PRIVATE(have_privkey) )
	{
	return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
	}

	if ( ctx->MBEDTLS_PRIVATE(type) != MBEDTLS_LMOTS_SHA256_N32_W8 ) {
	return( MBEDTLS_ERR_LMOTS_BAD_INPUT_DATA );
	}

	memcpy( ctx->MBEDTLS_PRIVATE(I_key_identifier), I_key_identifier,
	sizeof( ctx->MBEDTLS_PRIVATE(I_key_identifier) ) );

	ctx->MBEDTLS_PRIVATE(q_leaf_identifier) = q_leaf_identifier;

	val_to_network_bytes( ctx->MBEDTLS_PRIVATE(q_leaf_identifier), MBEDTLS_LMOTS_Q_LEAF_ID_LEN,
	ctx->MBEDTLS_PRIVATE(q_leaf_identifier_bytes) );

	val_to_network_bytes( 0xFF, sizeof( const_bytes ), const_bytes );

	for ( i_symbol_idx = 0; i_symbol_idx < MBEDTLS_LMOTS_P_SIG_SYMBOL_LEN; i_symbol_idx++ )
	{
	mbedtls_md_init( &hash_ctx );
	ret = mbedtls_md_setup( &hash_ctx, mbedtls_md_info_from_type( MBEDTLS_MD_SHA256 ), 0 );
	if( ret )
	{
	goto out;
	}
	ret = mbedtls_md_starts( &hash_ctx );
	if ( ret )
	{
	goto out;
	}

	ret = mbedtls_md_update( &hash_ctx, ctx->MBEDTLS_PRIVATE(I_key_identifier),
	sizeof( ctx->MBEDTLS_PRIVATE(I_key_identifier) ) );
	if ( ret ) {
	goto out;
	}

	ret = mbedtls_md_update( &hash_ctx, ctx->MBEDTLS_PRIVATE(q_leaf_identifier_bytes),
	sizeof( ctx->MBEDTLS_PRIVATE(q_leaf_identifier_bytes) ) );
	if ( ret )
	{
	goto out;
	}

	val_to_network_bytes( i_symbol_idx, I_SYMBOL_IDX_LEN, i_symbol_idx_bytes );
	ret = mbedtls_md_update( &hash_ctx, i_symbol_idx_bytes, I_SYMBOL_IDX_LEN );
	if ( ret )
	{
	goto out;
	}

	ret = mbedtls_md_update( &hash_ctx, const_bytes, sizeof( const_bytes) );
	if ( ret )
	{
	goto out;
	}

	ret = mbedtls_md_update( &hash_ctx, seed, seed_len );
	if ( ret )
	{
	goto out;
	}

	ret = mbedtls_md_finish( &hash_ctx, ctx->MBEDTLS_PRIVATE(priv_key)[i_symbol_idx] );
	if ( ret )
	{
	goto out;
	}

	mbedtls_md_free( &hash_ctx);
	}

	ctx->MBEDTLS_PRIVATE(have_privkey) = 1;

	out:
	if( ret )
	{
	mbedtls_md_free( &hash_ctx );
	return( ret );
	}

	return ret;
	}

	#endif /* MBEDTLS_LMOTS_C */