diff --git a/platform-independent/c/cli/src/mpw-cli.c b/platform-independent/c/cli/src/mpw-cli.c
index 6472135f..80275d09 100644
--- a/platform-independent/c/cli/src/mpw-cli.c
+++ b/platform-independent/c/cli/src/mpw-cli.c
@@ -272,7 +272,7 @@ void cli_free(Arguments *args, Operation *operation) {
         mpw_free_strings( &operation->fullName, &operation->masterPassword, &operation->siteName, NULL );
         mpw_free_strings( &operation->keyContext, &operation->resultState, &operation->resultParam, NULL );
         mpw_free_strings( &operation->identicon, &operation->sitesPath, NULL );
-        mpw_marshal_free( &operation->file );
+        mpw_marshal_file_free( &operation->file );
         operation->site = NULL;
         operation->question = NULL;
         cli_masterKeyProvider_free();
@@ -487,7 +487,7 @@ void cli_user(Arguments *args, Operation *operation) {
     if (!sitesFile) {
         // If no user from mpsites, create a new one.
         mpw_free_string( &operation->sitesPath );
-        mpw_marshal_free( &operation->file );
+        mpw_marshal_file_free( &operation->file );
         operation->file = mpw_marshal_file( mpw_marshal_user(
                 operation->fullName, cli_masterKeyProvider_op( operation ), MPAlgorithmVersionCurrent ), NULL );
     }
@@ -501,7 +501,7 @@ void cli_user(Arguments *args, Operation *operation) {
 
         // Parse file.
         MPMarshalError marshalError = { .type = MPMarshalSuccess };
-        mpw_marshal_free( &operation->file );
+        mpw_marshal_file_free( &operation->file );
         operation->file = mpw_marshal_read( sitesInputData,
                 cli_masterKeyProvider_op( operation ), &marshalError );
         if (marshalError.type == MPMarshalErrorMasterPassword && operation->allowPasswordUpdate) {
@@ -516,7 +516,7 @@ void cli_user(Arguments *args, Operation *operation) {
                     importMasterPassword = mpw_getpass( "Old master password: " );
                 }
 
-                mpw_marshal_free( &operation->file );
+                mpw_marshal_file_free( &operation->file );
                 operation->file = mpw_marshal_read( sitesInputData,
                         cli_masterKeyProvider_str( importMasterPassword ), &marshalError );
                 if (operation->file && operation->file->user)
diff --git a/platform-independent/c/core/src/mpw-algorithm.c b/platform-independent/c/core/src/mpw-algorithm.c
index a214d8f8..19329c35 100644
--- a/platform-independent/c/core/src/mpw-algorithm.c
+++ b/platform-independent/c/core/src/mpw-algorithm.c
@@ -22,7 +22,7 @@
 #include "mpw-algorithm_v2.c"
 #include "mpw-algorithm_v3.c"
 
-MPMasterKey mpw_master_key(const char *fullName, const char *masterPassword, const MPAlgorithmVersion algorithmVersion) {
+const MPMasterKey mpw_master_key(const char *fullName, const char *masterPassword, const MPAlgorithmVersion algorithmVersion) {
 
     if (fullName && !strlen( fullName ))
         fullName = NULL;
@@ -56,8 +56,8 @@ MPMasterKey mpw_master_key(const char *fullName, const char *masterPassword, con
     }
 }
 
-MPSiteKey mpw_site_key(
-        MPMasterKey masterKey, const char *siteName, const MPCounterValue siteCounter,
+const MPSiteKey mpw_site_key(
+        const MPMasterKey masterKey, const char *siteName, const MPCounterValue siteCounter,
         const MPKeyPurpose keyPurpose, const char *keyContext, const MPAlgorithmVersion algorithmVersion) {
 
     if (keyContext && !strlen( keyContext ))
@@ -93,7 +93,7 @@ MPSiteKey mpw_site_key(
 }
 
 const char *mpw_site_result(
-        MPMasterKey masterKey, const char *siteName, const MPCounterValue siteCounter,
+        const MPMasterKey masterKey, const char *siteName, const MPCounterValue siteCounter,
         const MPKeyPurpose keyPurpose, const char *keyContext,
         const MPResultType resultType, const char *resultParam,
         const MPAlgorithmVersion algorithmVersion) {
@@ -171,7 +171,7 @@ const char *mpw_site_result(
 }
 
 const char *mpw_site_state(
-        MPMasterKey masterKey, const char *siteName, const MPCounterValue siteCounter,
+        const MPMasterKey masterKey, const char *siteName, const MPCounterValue siteCounter,
         const MPKeyPurpose keyPurpose, const char *keyContext,
         const MPResultType resultType, const char *resultParam,
         const MPAlgorithmVersion algorithmVersion) {
@@ -223,7 +223,7 @@ static const char *mpw_identicon_accessories[] = {
         "♨", "♩", "♪", "♫", "⚐", "⚑", "⚔", "⚖", "⚙", "⚠", "⌘", "⏎", "✄", "✆", "✈", "✉", "✌"
 };
 
-MPIdenticon mpw_identicon(const char *fullName, const char *masterPassword) {
+const MPIdenticon mpw_identicon(const char *fullName, const char *masterPassword) {
 
     const uint8_t *seed = NULL;
     if (fullName && strlen( fullName ) && masterPassword && strlen( masterPassword ))
@@ -246,7 +246,7 @@ MPIdenticon mpw_identicon(const char *fullName, const char *masterPassword) {
 }
 
 const char *mpw_identicon_encode(
-        MPIdenticon identicon) {
+        const MPIdenticon identicon) {
 
     if (identicon.color == MPIdenticonColorUnset)
         return "";
@@ -255,7 +255,7 @@ const char *mpw_identicon_encode(
             identicon.color, identicon.leftArm, identicon.body, identicon.rightArm, identicon.accessory );
 }
 
-MPIdenticon mpw_identicon_encoded(
+const MPIdenticon mpw_identicon_encoded(
         const char *encoding) {
 
     MPIdenticon identicon = MPIdenticonUnset;
diff --git a/platform-independent/c/core/src/mpw-algorithm.h b/platform-independent/c/core/src/mpw-algorithm.h
index 0a82b2d0..0d60cbd8 100644
--- a/platform-independent/c/core/src/mpw-algorithm.h
+++ b/platform-independent/c/core/src/mpw-algorithm.h
@@ -38,20 +38,20 @@ typedef mpw_enum( unsigned int, MPAlgorithmVersion ) {
 
 /** Derive the master key for a user based on their name and master password.
  * @return A buffer (allocated, MPMasterKeySize) or NULL if the fullName or masterPassword is missing, the algorithm is unknown, or an algorithm error occurred. */
-MPMasterKey mpw_master_key(
+const MPMasterKey mpw_master_key(
         const char *fullName, const char *masterPassword, const MPAlgorithmVersion algorithmVersion);
 
 /** Derive the site key for a user's site from the given master key and site parameters.
  * @return A buffer (allocated, MPSiteKeySize) or NULL if the masterKey or siteName is missing, the algorithm is unknown, or an algorithm error occurred. */
-MPSiteKey mpw_site_key(
-        MPMasterKey masterKey, const char *siteName, const MPCounterValue siteCounter,
+const MPSiteKey mpw_site_key(
+        const MPMasterKey masterKey, const char *siteName, const MPCounterValue siteCounter,
         const MPKeyPurpose keyPurpose, const char *keyContext, const MPAlgorithmVersion algorithmVersion);
 
 /** Generate a site result token from the given parameters.
  * @param resultParam A parameter for the resultType.  For stateful result types, the output of mpw_site_state.
  * @return A string (allocated) or NULL if the masterKey or siteName is missing, the algorithm is unknown, or an algorithm error occurred. */
 const char *mpw_site_result(
-        MPMasterKey masterKey, const char *siteName, const MPCounterValue siteCounter,
+        const MPMasterKey masterKey, const char *siteName, const MPCounterValue siteCounter,
         const MPKeyPurpose keyPurpose, const char *keyContext,
         const MPResultType resultType, const char *resultParam,
         const MPAlgorithmVersion algorithmVersion);
@@ -60,19 +60,19 @@ const char *mpw_site_result(
  * @param resultParam A parameter for the resultType.  For stateful result types, the desired mpw_site_result.
  * @return A string (allocated) or NULL if the masterKey, siteName or resultParam is missing, the algorithm is unknown, or an algorithm error occurred. */
 const char *mpw_site_state(
-        MPMasterKey masterKey, const char *siteName, const MPCounterValue siteCounter,
+        const MPMasterKey masterKey, const char *siteName, const MPCounterValue siteCounter,
         const MPKeyPurpose keyPurpose, const char *keyContext,
         const MPResultType resultType, const char *resultParam,
         const MPAlgorithmVersion algorithmVersion);
 
 /** @return An identicon (static) that represents the user's identity. */
-MPIdenticon mpw_identicon(
+const MPIdenticon mpw_identicon(
         const char *fullName, const char *masterPassword);
 /** @return An encoded representation (shared) of the given identicon or an empty string if the identicon is unset. */
 const char *mpw_identicon_encode(
-        MPIdenticon identicon);
+        const MPIdenticon identicon);
 /** @return An identicon (static) decoded from the given encoded identicon representation or an identicon with empty fields if the identicon could not be parsed. */
-MPIdenticon mpw_identicon_encoded(
+const MPIdenticon mpw_identicon_encoded(
         const char *encoding);
 
 #endif // _MPW_ALGORITHM_H
diff --git a/platform-independent/c/core/src/mpw-marshal-util.c b/platform-independent/c/core/src/mpw-marshal-util.c
index ce94e529..7d2d5cb9 100644
--- a/platform-independent/c/core/src/mpw-marshal-util.c
+++ b/platform-independent/c/core/src/mpw-marshal-util.c
@@ -23,7 +23,7 @@ MP_LIBS_BEGIN
 #include <string.h>
 MP_LIBS_END
 
-char *mpw_get_token(const char **in, const char *eol, char *delim) {
+char *mpw_get_token(const char **in, const char *eol, const char *delim) {
 
     // Skip leading spaces.
     for (; **in == ' '; ++*in);
@@ -60,7 +60,7 @@ time_t mpw_timegm(const char *time) {
 #if MPW_JSON
 
 json_object *mpw_get_json_object(
-        json_object *obj, const char *key, bool create) {
+        json_object *obj, const char *key, const bool create) {
 
     if (!obj)
         return NULL;
@@ -86,7 +86,7 @@ const char *mpw_get_json_string(
 }
 
 int64_t mpw_get_json_int(
-        json_object *obj, const char *key, int64_t defaultValue) {
+        json_object *obj, const char *key, const int64_t defaultValue) {
 
     json_object *json_value = mpw_get_json_object( obj, key, false );
     if (!json_value)
@@ -96,7 +96,7 @@ int64_t mpw_get_json_int(
 }
 
 bool mpw_get_json_boolean(
-        json_object *obj, const char *key, bool defaultValue) {
+        json_object *obj, const char *key, const bool defaultValue) {
 
     json_object *json_value = mpw_get_json_object( obj, key, false );
     if (!json_value)
@@ -107,7 +107,7 @@ bool mpw_get_json_boolean(
 
 #endif
 
-bool mpw_update_master_key(MPMasterKey *masterKey, MPAlgorithmVersion *masterKeyAlgorithm, MPAlgorithmVersion targetKeyAlgorithm,
+bool mpw_update_master_key(MPMasterKey *masterKey, MPAlgorithmVersion *masterKeyAlgorithm, const MPAlgorithmVersion targetKeyAlgorithm,
         const char *fullName, const char *masterPassword) {
 
     if (masterKey && (!*masterKey || *masterKeyAlgorithm != targetKeyAlgorithm)) {
diff --git a/platform-independent/c/core/src/mpw-marshal-util.h b/platform-independent/c/core/src/mpw-marshal-util.h
index 4f35d9d8..ba076927 100644
--- a/platform-independent/c/core/src/mpw-marshal-util.h
+++ b/platform-independent/c/core/src/mpw-marshal-util.h
@@ -34,7 +34,7 @@ MP_LIBS_END
  * The input string reference is advanced beyond the token delimitor if one is found.
  * @return A string (allocated) containing the token or NULL if the delim wasn't found before eol. */
 char *mpw_get_token(
-        const char **in, const char *eol, char *delim);
+        const char **in, const char *eol, const char *delim);
 /** Convert an RFC 3339 time string into epoch time.
  * @return ERR if the string could not be parsed. */
 time_t mpw_timegm(
@@ -48,7 +48,7 @@ time_t mpw_timegm(
  * @param create If true, create and insert new objects for any missing path components.
  * @return An object (shared) or a new object (shared) installed in the tree if the path's object path was not found. */
 json_object *mpw_get_json_object(
-        json_object *obj, const char *key, bool create);
+        json_object *obj, const char *key, const bool create);
 /** Search for a string in a JSON object tree.
  * @param key A dot-delimited list of JSON object keys to walk toward the child object.
  * @return A string (shared) or defaultValue if one of the path's object keys was not found in the source object's tree. */
@@ -58,12 +58,12 @@ const char *mpw_get_json_string(
  * @param key A dot-delimited list of JSON object keys to walk toward the child object.
  * @return The integer value or defaultValue if one of the path's object keys was not found in the source object's tree. */
 int64_t mpw_get_json_int(
-        json_object *obj, const char *key, int64_t defaultValue);
+        json_object *obj, const char *key, const int64_t defaultValue);
 /** Search for a boolean in a JSON object tree.
  * @param key A dot-delimited list of JSON object keys to walk toward the child object.
  * @return The boolean value or defaultValue if one of the path's object keys was not found in the source object's tree. */
 bool mpw_get_json_boolean(
-        json_object *obj, const char *key, bool defaultValue);
+        json_object *obj, const char *key, const bool defaultValue);
 #endif
 
 /// mpw.
@@ -72,7 +72,7 @@ bool mpw_get_json_boolean(
  * @param masterKey A buffer (allocated, MPMasterKeySize).
  * @return false if an error occurred during the derivation of the master key. */
 bool mpw_update_master_key(
-        MPMasterKey *masterKey, MPAlgorithmVersion *masterKeyAlgorithm, MPAlgorithmVersion targetKeyAlgorithm,
+        MPMasterKey *masterKey, MPAlgorithmVersion *masterKeyAlgorithm, const MPAlgorithmVersion targetKeyAlgorithm,
         const char *fullName, const char *masterPassword);
 
 #endif // _MPW_MARSHAL_UTIL_H
diff --git a/platform-independent/c/core/src/mpw-marshal.c b/platform-independent/c/core/src/mpw-marshal.c
index e5551215..e6107d5c 100644
--- a/platform-independent/c/core/src/mpw-marshal.c
+++ b/platform-independent/c/core/src/mpw-marshal.c
@@ -120,75 +120,309 @@ MPMarshalledFile *mpw_marshal_file(
     return file;
 }
 
-bool mpw_marshal_info_free(
+void mpw_marshal_info_free(
         MPMarshalInfo **info) {
 
     if (!info || !*info)
-        return true;
+        return;
 
-    bool success = true;
-    success &= mpw_free_strings( &(*info)->fullName, &(*info)->keyID, NULL );
-    success &= mpw_free( info, sizeof( MPMarshalInfo ) );
-
-    return success;
+    mpw_free_strings( &(*info)->fullName, &(*info)->keyID, NULL );
+    mpw_free( info, sizeof( MPMarshalInfo ) );
 }
 
-static bool mpw_marshal_user_free(
+void mpw_marshal_user_free(
         MPMarshalledUser **user) {
 
     if (!user || !*user)
-        return true;
+        return;
 
-    bool success = mpw_free_strings( &(*user)->fullName, &(*user)->keyID, NULL );
+    mpw_free_strings( &(*user)->fullName, &(*user)->keyID, NULL );
 
     for (size_t s = 0; s < (*user)->sites_count; ++s) {
         MPMarshalledSite *site = &(*user)->sites[s];
-        success &= mpw_free_strings( &site->siteName, &site->resultState, &site->loginState, &site->url, NULL );
+        mpw_free_strings( &site->siteName, &site->resultState, &site->loginState, &site->url, NULL );
 
         for (size_t q = 0; q < site->questions_count; ++q) {
             MPMarshalledQuestion *question = &site->questions[q];
-            success &= mpw_free_strings( &question->keyword, &question->state, NULL );
+            mpw_free_strings( &question->keyword, &question->state, NULL );
         }
-        success &= mpw_free( &site->questions, sizeof( MPMarshalledQuestion ) * site->questions_count );
+        mpw_free( &site->questions, sizeof( MPMarshalledQuestion ) * site->questions_count );
     }
 
-    success &= mpw_free( &(*user)->sites, sizeof( MPMarshalledSite ) * (*user)->sites_count );
-    success &= mpw_free( user, sizeof( MPMarshalledUser ) );
-
-    return success;
+    mpw_free( &(*user)->sites, sizeof( MPMarshalledSite ) * (*user)->sites_count );
+    mpw_free( user, sizeof( MPMarshalledUser ) );
 }
 
-static bool mpw_marshal_data_null(
-        MPMarshalledData *data) {
-
-    if (!data)
-        return true;
-
-    bool success = mpw_free_strings( &data->key, &data->str_value, NULL );
-    for (unsigned int c = 0; c < data->children_count; ++c)
-        success &= mpw_marshal_data_null( &data->children[c] );
-    success &= mpw_free( &data->children, sizeof( MPMarshalledData ) * data->children_count );
-    data->children_count = 0;
-    data->num_value = NAN;
-    data->is_bool = false;
-    data->is_null = true;
-
-    return success;
-}
-
-bool mpw_marshal_free(
+void mpw_marshal_file_free(
         MPMarshalledFile **file) {
 
     if (!file || !*file)
-        return true;
+        return;
 
-    bool success = true;
+    mpw_marshal_info_free( &(*file)->info );
+    mpw_marshal_user_free( &(*file)->user );
+    if ((*file)->data) {
+        mpw_marshal_data_set_null( (*file)->data, NULL );
+        mpw_free_string( &(*file)->data->key );
+        mpw_free( &(*file)->data, sizeof( MPMarshalledData ) );
+    }
+    mpw_free( file, sizeof( MPMarshalledFile ) );
+}
 
-    success &= mpw_marshal_info_free( &(*file)->info );
-    success &= mpw_marshal_user_free( &(*file)->user );
-    success &= mpw_marshal_data_null( (*file)->data );
-    success &= mpw_free( &(*file)->data, sizeof( MPMarshalledData ) );
-    success &= mpw_free( file, sizeof( MPMarshalledFile ) );
+MPMarshalledData *mpw_marshal_data_new() {
+
+    MPMarshalledData *data = malloc( sizeof( MPMarshalledData ) );
+    *data = (MPMarshalledData){};
+    mpw_marshal_data_set_null( data, NULL );
+    return data;
+}
+
+MPMarshalledData *mpw_marshal_data_vget(
+        MPMarshalledData *data, va_list nodes) {
+
+    MPMarshalledData *parent = data, *child;
+    for (const char *node; parent && (node = va_arg( nodes, const char * )); parent = child) {
+        child = NULL;
+
+        for (size_t c = 0; c < parent->children_count; ++c) {
+            const char *key = parent->children[c].key;
+            if (key && strcmp( node, key ) == OK) {
+                child = &parent->children[c];
+                break;
+            }
+        }
+
+        if (!child) {
+            if (!mpw_realloc( &parent->children, NULL, sizeof( MPMarshalledData ) * ++parent->children_count )) {
+                --parent->children_count;
+                break;
+            }
+            *(child = &parent->children[parent->children_count - 1]) = (MPMarshalledData){ .key = mpw_strdup( node ) };
+            mpw_marshal_data_set_null( child, NULL );
+            child->is_null = false;
+        }
+    }
+
+    return parent;
+}
+
+MPMarshalledData *mpw_marshal_data_get(
+        MPMarshalledData *data, ...) {
+
+    va_list nodes;
+    va_start( nodes, data );
+    MPMarshalledData *child = mpw_marshal_data_vget( data, nodes );
+    va_end( nodes );
+
+    return child;
+}
+
+const MPMarshalledData *mpw_marshal_data_vfind(
+        const MPMarshalledData *data, va_list nodes) {
+
+    const MPMarshalledData *parent = data, *child;
+    for (const char *node; parent && (node = va_arg( nodes, const char * )); parent = child) {
+        child = NULL;
+
+        for (size_t c = 0; c < parent->children_count; ++c) {
+            const char *key = parent->children[c].key;
+            if (key && strcmp( node, key ) == OK) {
+                child = &parent->children[c];
+                break;
+            }
+        }
+
+        if (!child)
+            break;
+    }
+
+    return parent;
+}
+
+const MPMarshalledData *mpw_marshal_data_find(
+        const MPMarshalledData *data, ...) {
+
+    va_list nodes;
+    va_start( nodes, data );
+    const MPMarshalledData *child = mpw_marshal_data_vfind( data, nodes );
+    va_end( nodes );
+
+    return child;
+}
+
+bool mpw_marshal_data_vis_null(
+        const MPMarshalledData *data, va_list nodes) {
+
+    const MPMarshalledData *child = mpw_marshal_data_vfind( data, nodes );
+    return !child || child->is_null;
+}
+
+bool mpw_marshal_data_is_null(
+        const MPMarshalledData *data, ...) {
+
+    va_list nodes;
+    va_start( nodes, data );
+    bool value = mpw_marshal_data_vis_null( data, nodes );
+    va_end( nodes );
+
+    return value;
+}
+
+bool mpw_marshal_data_vset_null(
+        MPMarshalledData *data, va_list nodes) {
+
+    MPMarshalledData *child = mpw_marshal_data_vget( data, nodes );
+    if (!child)
+        return false;
+
+    mpw_free_string( &child->str_value );
+    for (unsigned int c = 0; c < child->children_count; ++c) {
+        mpw_marshal_data_set_null( &child->children[c], NULL );
+        mpw_free_string( &child->children[c].key );
+    }
+    mpw_free( &child->children, sizeof( MPMarshalledData ) * child->children_count );
+    child->children_count = 0;
+    child->num_value = NAN;
+    child->is_bool = false;
+    child->is_null = true;
+    return true;
+}
+
+bool mpw_marshal_data_set_null(
+        MPMarshalledData *data, ...) {
+
+    va_list nodes;
+    va_start( nodes, data );
+    bool success = mpw_marshal_data_vset_null( data, nodes );
+    va_end( nodes );
+
+    return success;
+}
+
+bool mpw_marshal_data_vget_bool(
+        const MPMarshalledData *data, va_list nodes) {
+
+    const MPMarshalledData *child = mpw_marshal_data_vfind( data, nodes );
+    return child && child->is_bool && child->num_value != false;
+}
+
+bool mpw_marshal_data_get_bool(
+        const MPMarshalledData *data, ...) {
+
+    va_list nodes;
+    va_start( nodes, data );
+    bool value = mpw_marshal_data_vget_bool( data, nodes );
+    va_end( nodes );
+
+    return value;
+}
+
+bool mpw_marshal_data_vset_bool(
+        const bool value, MPMarshalledData *data, va_list nodes) {
+
+    MPMarshalledData *child = mpw_marshal_data_vget( data, nodes );
+    if (!child || !mpw_marshal_data_set_null( child, NULL ))
+        return false;
+
+    child->is_null = false;
+    child->is_bool = true;
+    child->num_value = value != false;
+    return true;
+}
+
+bool mpw_marshal_data_set_bool(
+        const bool value, MPMarshalledData *data, ...) {
+
+    va_list nodes;
+    va_start( nodes, data );
+    bool success = mpw_marshal_data_vset_bool( value, data, nodes );
+    va_end( nodes );
+
+    return success;
+}
+
+double mpw_marshal_data_vget_num(
+        const MPMarshalledData *data, va_list nodes) {
+
+    const MPMarshalledData *child = mpw_marshal_data_vfind( data, nodes );
+    return child == NULL? NAN: child->num_value;
+}
+
+double mpw_marshal_data_get_num(
+        const MPMarshalledData *data, ...) {
+
+    va_list nodes;
+    va_start( nodes, data );
+    double value = mpw_marshal_data_vget_num( data, nodes );
+    va_end( nodes );
+
+    return value;
+}
+
+bool mpw_marshal_data_vset_num(
+        const double value, MPMarshalledData *data, va_list nodes) {
+
+    MPMarshalledData *child = mpw_marshal_data_vget( data, nodes );
+    if (!child || !mpw_marshal_data_set_null( child, NULL ))
+        return false;
+
+    child->is_null = false;
+    child->num_value = value;
+    child->str_value = mpw_strdup( mpw_str( "%g", value ) );
+    return true;
+}
+
+bool mpw_marshal_data_set_num(
+        const double value, MPMarshalledData *data, ...) {
+
+    va_list nodes;
+    va_start( nodes, data );
+    bool success = mpw_marshal_data_vset_num( value, data, nodes );
+    va_end( nodes );
+
+    return success;
+}
+
+const char *mpw_marshal_data_vget_str(
+        const MPMarshalledData *data, va_list nodes) {
+
+    const MPMarshalledData *child = mpw_marshal_data_vfind( data, nodes );
+    return child == NULL? NULL: mpw_strdup( child->str_value );
+}
+
+const char *mpw_marshal_data_get_str(
+        const MPMarshalledData *data, ...) {
+
+    va_list nodes;
+    va_start( nodes, data );
+    const char *value = mpw_marshal_data_vget_str( data, nodes );
+    va_end( nodes );
+
+    return value;
+}
+
+bool mpw_marshal_data_vset_str(
+        const char *value, MPMarshalledData *data, va_list nodes) {
+
+    MPMarshalledData *child = mpw_marshal_data_vget( data, nodes );
+    if (!child || !mpw_marshal_data_set_null( child, NULL ))
+        return false;
+
+    if (value) {
+        child->is_null = false;
+        child->str_value = mpw_strdup( value );
+    }
+
+    return true;
+}
+
+bool mpw_marshal_data_set_str(
+        const char *value, MPMarshalledData *data, ...) {
+
+    va_list nodes;
+    va_start( nodes, data );
+    bool success = mpw_marshal_data_vset_str( value, data, nodes );
+    va_end( nodes );
 
     return success;
 }
@@ -285,20 +519,24 @@ static const char *mpw_marshal_write_flat(
 #if MPW_JSON
 
 static json_object *mpw_get_json_data(
-        MPMarshalledData *data) {
+        const MPMarshalledData *data) {
 
     if (!data || data->is_null)
         return NULL;
     if (data->is_bool)
         return json_object_new_boolean( data->num_value != false );
-    if (!isnan( data->num_value ))
-        return json_object_new_double_s( data->num_value, data->str_value );
+    if (!isnan( data->num_value )) {
+        if (data->str_value)
+            return json_object_new_double_s( data->num_value, data->str_value );
+        else
+            return json_object_new_double( data->num_value );
+    }
     if (data->str_value)
         return json_object_new_string( data->str_value );
 
     json_object *obj = NULL;
-    for (size_t index = 0; index < data->children_count; ++index) {
-        MPMarshalledData *child = &data->children[index];
+    for (size_t c = 0; c < data->children_count; ++c) {
+        MPMarshalledData *child = &data->children[c];
         if (!obj) {
             if (child->key)
                 obj = json_object_new_object();
@@ -505,8 +743,8 @@ static void mpw_marshal_read_flat_info(
                 break;
 
             // Header
-            char *headerName = mpw_get_token( &positionInLine, endOfLine, ":\n" );
-            char *headerValue = mpw_get_token( &positionInLine, endOfLine, "\n" );
+            const char *headerName = mpw_get_token( &positionInLine, endOfLine, ":\n" );
+            const char *headerValue = mpw_get_token( &positionInLine, endOfLine, "\n" );
             if (!headerName || !headerValue)
                 continue;
 
@@ -605,8 +843,8 @@ static MPMarshalledFile *mpw_marshal_read_flat(
             }
 
             // Header
-            char *headerName = mpw_get_token( &positionInLine, endOfLine, ":\n" );
-            char *headerValue = mpw_get_token( &positionInLine, endOfLine, "\n" );
+            const char *headerName = mpw_get_token( &positionInLine, endOfLine, ":\n" );
+            const char *headerValue = mpw_get_token( &positionInLine, endOfLine, "\n" );
             if (!headerName || !headerValue) {
                 error->type = MPMarshalErrorStructure;
                 error->message = mpw_str( "Invalid header: %s", mpw_strndup( positionInLine, (size_t)(endOfLine - positionInLine) ) );
@@ -672,8 +910,8 @@ static MPMarshalledFile *mpw_marshal_read_flat(
             continue;
 
         // Site
-        char *siteName = NULL, *siteResultState = NULL, *siteLoginState = NULL;
-        char *str_lastUsed = NULL, *str_uses = NULL, *str_type = NULL, *str_algorithm = NULL, *str_counter = NULL;
+        const char *siteName = NULL, *siteResultState = NULL, *siteLoginState = NULL;
+        const char *str_lastUsed = NULL, *str_uses = NULL, *str_type = NULL, *str_algorithm = NULL, *str_counter = NULL;
         switch (format) {
             case 0: {
                 str_lastUsed = mpw_get_token( &positionInLine, endOfLine, " \t\n" );
@@ -834,6 +1072,9 @@ static MPMarshalledFile *mpw_marshal_read_flat(
 static void mpw_set_json_data(
         MPMarshalledData *data, json_object *obj) {
 
+    if (!data)
+        return;
+
     json_type type = json_object_get_type( obj );
     data->is_null = type == json_type_null;
     data->is_bool = type == json_type_boolean;
@@ -860,16 +1101,15 @@ static void mpw_set_json_data(
     size_t newChildrenCount = 0;
     for (size_t c = 0; c < data->children_count; ++c) {
         MPMarshalledData *child = &data->children[c];
-        if ((type != json_type_object && type != json_type_array) ||
-            (child->key && type != json_type_object) || (!isnan( child->index ) && type != json_type_array)) {
-            mpw_marshal_data_null( child );
-            if (!newChildren) {
-                newChildren = malloc( sizeof( MPMarshalledData ) * newChildrenCount );
-                if (newChildren)
-                    memcpy( newChildren, data->children, sizeof( MPMarshalledData ) * newChildrenCount );
-            }
+        if ((type != json_type_object && type != json_type_array) || (child->key && type != json_type_object)) {
+            // Not a valid child in this object, remove it.
+            mpw_marshal_data_set_null( child, NULL );
+            mpw_free_string( &child->key );
+            if (!newChildren)
+                newChildren = mpw_memdup( data->children, sizeof( MPMarshalledData ) * newChildrenCount );
         }
         else {
+            // Valid child in this object, keep it.
             ++newChildrenCount;
             if (newChildren) {
                 if (!mpw_realloc( &newChildren, NULL, sizeof( MPMarshalledData ) * newChildrenCount )) {
@@ -896,7 +1136,7 @@ static void mpw_set_json_data(
             // Find existing child.
             for (size_t c = 0; c < data->children_count; ++c)
                 if (data->children[c].key == entry.key ||
-                    (data->children[c].key && entry.key && strcmp( data->children[c].key, entry.key )) == OK) {
+                    (data->children[c].key && entry.key && strcmp( data->children[c].key, entry.key ) == OK)) {
                     child = &data->children[c];
                     break;
                 }
@@ -965,7 +1205,7 @@ static void mpw_marshal_read_json_info(
 }
 
 static MPMarshalledFile *mpw_marshal_read_json(
-        const char *in, MPMasterKeyProvider masterKeyProvider, MPMarshalError *error) {
+        const char *in, const MPMasterKeyProvider masterKeyProvider, MPMarshalError *error) {
 
     *error = (MPMarshalError){ MPMarshalErrorInternal, "Unexpected internal error." };
     if (!in || !strlen( in )) {
@@ -1173,11 +1413,8 @@ static MPMarshalledFile *mpw_marshal_read_json(
     }
     mpw_free( &masterKey, MPMasterKeySize );
 
-    MPMarshalledData *data = malloc( sizeof( MPMarshalledData ) );
-    if (data) {
-        *data = (MPMarshalledData){};
-        mpw_set_json_data( data, json_file );
-    }
+    MPMarshalledData *data = mpw_marshal_data_new();
+    mpw_set_json_data( data, json_file );
     json_object_put( json_file );
 
     MPMarshalledFile *file = mpw_marshal_file( user, data );
@@ -1223,7 +1460,7 @@ MPMarshalInfo *mpw_marshal_read_info(
 }
 
 MPMarshalledFile *mpw_marshal_read(
-        const char *in, MPMasterKeyProvider masterKeyProvider, MPMarshalError *error) {
+        const char *in, const MPMasterKeyProvider masterKeyProvider, MPMarshalError *error) {
 
     MPMarshalInfo *info = mpw_marshal_read_info( in );
     if (!info)
@@ -1314,10 +1551,10 @@ const char **mpw_marshal_format_extensions(
             return NULL;
         case MPMarshalFormatFlat:
             return mpw_strings( count,
-                    mpw_marshal_format_extension( format ), "mpsites.txt", "txt" );
+                    mpw_marshal_format_extension( format ), "mpsites.txt", "txt", NULL );
         case MPMarshalFormatJSON:
             return mpw_strings( count,
-                    mpw_marshal_format_extension( format ), "mpsites.json", "json" );
+                    mpw_marshal_format_extension( format ), "mpsites.json", "json", NULL );
         default: {
             dbg( "Unknown format: %d", format );
             return NULL;
diff --git a/platform-independent/c/core/src/mpw-marshal.h b/platform-independent/c/core/src/mpw-marshal.h
index 4c4d40d1..aad8342a 100644
--- a/platform-independent/c/core/src/mpw-marshal.h
+++ b/platform-independent/c/core/src/mpw-marshal.h
@@ -23,6 +23,7 @@
 
 MP_LIBS_BEGIN
 #include <time.h>
+#include <stdarg.h>
 MP_LIBS_END
 
 //// Types.
@@ -161,14 +162,14 @@ MPMarshalInfo *mpw_marshal_read_info(
 /** Unmarshall sites in the given input buffer by parsing it using the given marshalling format.
  * @return A user object (allocated), or NULL if the format provides no marshalling or a format error occurred. */
 MPMarshalledFile *mpw_marshal_read(
-        const char *in, MPMasterKeyProvider masterKeyProvider, MPMarshalError *error);
+        const char *in, const MPMasterKeyProvider masterKeyProvider, MPMarshalError *error);
 
-//// Utilities.
+//// Creating.
 
 /** Create a new user object ready for marshalling.
  * @return A user object (allocated), or NULL if the fullName is missing or the marshalled user couldn't be allocated. */
 MPMarshalledUser *mpw_marshal_user(
-        const char *fullName, MPMasterKeyProvider masterKeyProvider, const MPAlgorithmVersion algorithmVersion);
+        const char *fullName, const MPMasterKeyProvider masterKeyProvider, const MPAlgorithmVersion algorithmVersion);
 /** Create a new site attached to the given user object, ready for marshalling.
  * @return A site object (allocated), or NULL if the siteName is missing or the marshalled site couldn't be allocated. */
 MPMarshalledSite *mpw_marshal_site(
@@ -183,11 +184,77 @@ MPMarshalledQuestion *mpw_marshal_question(
 MPMarshalledFile *mpw_marshal_file(
         MPMarshalledUser *user, MPMarshalledData *data);
 
+//// Disposing.
+
 /** Free the given user object and all associated data. */
-bool mpw_marshal_info_free(
+void mpw_marshal_info_free(
         MPMarshalInfo **info);
-bool mpw_marshal_free(
-        MPMarshalledFile **user);
+void mpw_marshal_user_free(
+        MPMarshalledUser **user);
+void mpw_marshal_file_free(
+        MPMarshalledFile **file);
+
+//// Exploring.
+
+/** Create a null value.
+ * @return A new data value (allocated), initialized to a null value, or NULL if the value couldn't be allocated. */
+MPMarshalledData *mpw_marshal_data_new(void);
+/** Get or create a value for the given path in the data store.
+ * @return The value at this path (shared), or NULL if the value didn't exist and couldn't be created. */
+MPMarshalledData *mpw_marshal_data_get(
+        MPMarshalledData *data, ...);
+MPMarshalledData *mpw_marshal_data_vget(
+        MPMarshalledData *data, va_list nodes);
+/** Look up the value at the given path in the data store.
+ * @return The value at this path (shared), or NULL if there is no value at this path. */
+const MPMarshalledData *mpw_marshal_data_find(
+        const MPMarshalledData *data, ...);
+const MPMarshalledData *mpw_marshal_data_vfind(
+        const MPMarshalledData *data, va_list nodes);
+/** Check if the data represents a NULL value.
+ * @return true if the value at this path is null or is missing, false if it is a non-null type. */
+bool mpw_marshal_data_is_null(
+        const MPMarshalledData *data, ...);
+bool mpw_marshal_data_vis_null(
+        const MPMarshalledData *data, va_list nodes);
+/** Set a null value at the given path in the data store.
+ * @return true if the object was successfully modified. */
+bool mpw_marshal_data_set_null(
+        MPMarshalledData *data, ...);
+bool mpw_marshal_data_vset_null(
+        MPMarshalledData *data, va_list nodes);
+/** Look up the boolean value at the given path in the data store.
+ * @return true if the value at this path is true, false if it is not or there is no boolean value at this path. */
+bool mpw_marshal_data_get_bool(
+        const MPMarshalledData *data, ...);
+bool mpw_marshal_data_vget_bool(
+        const MPMarshalledData *data, va_list nodes);
+/** Set a boolean value at the given path in the data store.
+ * @return true if the object was successfully modified. */
+bool mpw_marshal_data_set_bool(
+        const bool value, MPMarshalledData *data, ...);
+bool mpw_marshal_data_vset_bool(
+        const bool value, MPMarshalledData *data, va_list nodes);
+/** Look up the numeric value at the given path in the data store.
+ * @return A number or NAN if there is no numeric value at this path. */
+double mpw_marshal_data_get_num(
+        const MPMarshalledData *data, ...);
+double mpw_marshal_data_vget_num(
+        const MPMarshalledData *data, va_list nodes);
+bool mpw_marshal_data_set_num(
+        const double value, MPMarshalledData *data, ...);
+bool mpw_marshal_data_vset_num(
+        const double value, MPMarshalledData *data, va_list nodes);
+/** Look up the string value at the given path in the data store.
+ * @return The string value (allocated) or string representation of the number at this path; NULL if there is no such value at this path. */
+const char *mpw_marshal_data_get_str(
+        const MPMarshalledData *data, ...);
+const char *mpw_marshal_data_vget_str(
+        const MPMarshalledData *data, va_list nodes);
+bool mpw_marshal_data_set_str(
+        const char *value, MPMarshalledData *data, ...);
+bool mpw_marshal_data_vset_str(
+        const char *value, MPMarshalledData *data, va_list nodes);
 
 //// Format.
 
diff --git a/platform-independent/c/core/src/mpw-types.c b/platform-independent/c/core/src/mpw-types.c
index 006d9491..3eaf4341 100644
--- a/platform-independent/c/core/src/mpw-types.c
+++ b/platform-independent/c/core/src/mpw-types.c
@@ -90,7 +90,7 @@ const MPResultType mpw_type_named(const char *typeName) {
     return (MPResultType)ERR;
 }
 
-const char *mpw_type_abbreviation(MPResultType resultType) {
+const char *mpw_type_abbreviation(const MPResultType resultType) {
 
     switch (resultType) {
         case MPResultTypeTemplateMaximum:
@@ -122,7 +122,7 @@ const char *mpw_type_abbreviation(MPResultType resultType) {
     }
 }
 
-const char *mpw_type_short_name(MPResultType resultType) {
+const char *mpw_type_short_name(const MPResultType resultType) {
 
     switch (resultType) {
         case MPResultTypeTemplateMaximum:
@@ -154,7 +154,7 @@ const char *mpw_type_short_name(MPResultType resultType) {
     }
 }
 
-const char *mpw_type_long_name(MPResultType resultType) {
+const char *mpw_type_long_name(const MPResultType resultType) {
 
     switch (resultType) {
         case MPResultTypeTemplateMaximum:
@@ -186,7 +186,7 @@ const char *mpw_type_long_name(MPResultType resultType) {
     }
 }
 
-const char **mpw_type_templates(MPResultType type, size_t *count) {
+const char **mpw_type_templates(const MPResultType type, size_t *count) {
 
     if (!(type & MPResultTypeClassTemplate)) {
         dbg( "Not a generated type: %d", type );
@@ -231,7 +231,7 @@ const char **mpw_type_templates(MPResultType type, size_t *count) {
     }
 }
 
-const char *mpw_type_template(MPResultType type, uint8_t templateIndex) {
+const char *mpw_type_template(const MPResultType type, const uint8_t templateIndex) {
 
     size_t count = 0;
     const char **templates = mpw_type_templates( type, &count );
@@ -254,7 +254,7 @@ const MPKeyPurpose mpw_purpose_named(const char *purposeName) {
     return (MPKeyPurpose)ERR;
 }
 
-const char *mpw_purpose_name(MPKeyPurpose purpose) {
+const char *mpw_purpose_name(const MPKeyPurpose purpose) {
 
     switch (purpose) {
         case MPKeyPurposeAuthentication:
@@ -270,7 +270,7 @@ const char *mpw_purpose_name(MPKeyPurpose purpose) {
     }
 }
 
-const char *mpw_purpose_scope(MPKeyPurpose purpose) {
+const char *mpw_purpose_scope(const MPKeyPurpose purpose) {
 
     switch (purpose) {
         case MPKeyPurposeAuthentication:
@@ -286,7 +286,7 @@ const char *mpw_purpose_scope(MPKeyPurpose purpose) {
     }
 }
 
-const char *mpw_class_characters(char characterClass) {
+const char *mpw_class_characters(const char characterClass) {
 
     switch (characterClass) {
         case 'V':
@@ -316,7 +316,7 @@ const char *mpw_class_characters(char characterClass) {
     }
 }
 
-const char mpw_class_character(char characterClass, uint8_t seedByte) {
+const char mpw_class_character(const char characterClass, const uint8_t seedByte) {
 
     const char *classCharacters = mpw_class_characters( characterClass );
     if (!classCharacters || !strlen( classCharacters ))
diff --git a/platform-independent/c/core/src/mpw-types.h b/platform-independent/c/core/src/mpw-types.h
index b69588f7..3d71f060 100644
--- a/platform-independent/c/core/src/mpw-types.h
+++ b/platform-independent/c/core/src/mpw-types.h
@@ -152,11 +152,11 @@ const MPKeyPurpose mpw_purpose_named(const char *purposeName);
 /**
  * @return The standard name (static) for the given purpose or NULL if the purpose is not known.
  */
-const char *mpw_purpose_name(MPKeyPurpose purpose);
+const char *mpw_purpose_name(const MPKeyPurpose purpose);
 /**
  * @return The scope identifier (static) to apply when encoding for the given purpose or NULL if the purpose is not known.
  */
-const char *mpw_purpose_scope(MPKeyPurpose purpose);
+const char *mpw_purpose_scope(const MPKeyPurpose purpose);
 
 /**
  * @return The password type represented by the given name or ERR if the name does not represent a known type.
@@ -165,34 +165,34 @@ const MPResultType mpw_type_named(const char *typeName);
 /**
  * @return The standard identifying name (static) for the given password type or NULL if the type is not known.
  */
-const char *mpw_type_abbreviation(MPResultType resultType);
+const char *mpw_type_abbreviation(const MPResultType resultType);
 /**
  * @return The standard identifying name (static) for the given password type or NULL if the type is not known.
  */
-const char *mpw_type_short_name(MPResultType resultType);
+const char *mpw_type_short_name(const MPResultType resultType);
 /**
  * @return The descriptive name (static) for the given password type or NULL if the type is not known.
  */
-const char *mpw_type_long_name(MPResultType resultType);
+const char *mpw_type_long_name(const MPResultType resultType);
 
 /**
  * @return An array (allocated, count) of strings (static) that express the templates to use for the given type.
  *         NULL if the type is not known or is not a MPResultTypeClassTemplate.
  */
-const char **mpw_type_templates(MPResultType type, size_t *count);
+const char **mpw_type_templates(const MPResultType type, size_t *count);
 /**
  * @return A string (static) that contains the password encoding template of the given type for a seed that starts with the given byte.
  *         NULL if the type is not known or is not a MPResultTypeClassTemplate.
  */
-const char *mpw_type_template(MPResultType type, uint8_t templateIndex);
+const char *mpw_type_template(const MPResultType type, const uint8_t templateIndex);
 
 /**
  * @return An string (static) with all the characters in the given character class or NULL if the character class is not known.
  */
-const char *mpw_class_characters(char characterClass);
+const char *mpw_class_characters(const char characterClass);
 /**
  * @return A character from given character class that encodes the given byte or NUL if the character class is not known or is empty.
  */
-const char mpw_class_character(char characterClass, uint8_t seedByte);
+const char mpw_class_character(const char characterClass, const uint8_t seedByte);
 
 #endif // _MPW_TYPES_H
diff --git a/platform-independent/c/core/src/mpw-util.c b/platform-independent/c/core/src/mpw-util.c
index 40a8b48a..2812fcc7 100644
--- a/platform-independent/c/core/src/mpw-util.c
+++ b/platform-independent/c/core/src/mpw-util.c
@@ -175,7 +175,7 @@ bool __mpw_free(void **buffer, const size_t bufferSize) {
 
 bool __mpw_free_string(char **string) {
 
-    return *string && __mpw_free( (void **)string, strlen( *string ) );
+    return string && *string && __mpw_free( (void **)string, strlen( *string ) );
 }
 
 bool __mpw_free_strings(char **strings, ...) {
@@ -193,7 +193,7 @@ bool __mpw_free_strings(char **strings, ...) {
 }
 
 uint8_t const *mpw_kdf_scrypt(const size_t keySize, const uint8_t *secret, const size_t secretSize, const uint8_t *salt, const size_t saltSize,
-        uint64_t N, uint32_t r, uint32_t p) {
+        const uint64_t N, const uint32_t r, const uint32_t p) {
 
     if (!secret || !salt || !secretSize || !saltSize)
         return NULL;
@@ -367,7 +367,7 @@ const char *mpw_hotp(const uint8_t *key, size_t keySize, uint64_t movingFactor,
 }
 #endif
 
-MPKeyID mpw_id_buf(const void *buf, size_t length) {
+const MPKeyID mpw_id_buf(const void *buf, const size_t length) {
 
     if (!buf)
         return NULL;
@@ -443,7 +443,7 @@ const char *mpw_vstr(const char *format, va_list args) {
     return str_str[str_str_i];
 }
 
-const char *mpw_hex(const void *buf, size_t length) {
+const char *mpw_hex(const void *buf, const size_t length) {
 
     if (!buf || !length)
         return NULL;
@@ -461,7 +461,7 @@ const char *mpw_hex(const void *buf, size_t length) {
     return mpw_hex_buf[mpw_hex_buf_i];
 }
 
-const char *mpw_hex_l(uint32_t number) {
+const char *mpw_hex_l(const uint32_t number) {
 
     uint8_t buf[4 /* 32 / 8 */];
     buf[0] = (uint8_t)((number >> 24) & UINT8_MAX);
@@ -496,7 +496,7 @@ size_t mpw_utf8_strchars(const char *utf8String) {
     return strchars;
 }
 
-void *mpw_memdup(const void *src, size_t len) {
+void *mpw_memdup(const void *src, const size_t len) {
 
     if (!src)
         return NULL;
@@ -517,7 +517,7 @@ char *mpw_strdup(const char *src) {
     return mpw_memdup( src, len + 1 );
 }
 
-char *mpw_strndup(const char *src, size_t max) {
+char *mpw_strndup(const char *src, const size_t max) {
 
     if (!src)
         return NULL;
@@ -525,8 +525,7 @@ char *mpw_strndup(const char *src, size_t max) {
     size_t len = 0;
     for (; len < max && src[len] != '\0'; ++len);
 
-    char *dst = malloc( len + 1 );
-    memcpy( dst, src, len );
+    char *dst = mpw_memdup( src, len + 1 );
     dst[len] = '\0';
 
     return dst;
diff --git a/platform-independent/c/core/src/mpw-util.h b/platform-independent/c/core/src/mpw-util.h
index e8bfe866..b687e480 100644
--- a/platform-independent/c/core/src/mpw-util.h
+++ b/platform-independent/c/core/src/mpw-util.h
@@ -122,7 +122,7 @@ bool mpw_string_push(
 bool mpw_string_pushf(
         char **string, const char *pushFormat, ...);
 
-// These defines merely exist to force the void** cast (& do type-checking), since void** casts are not automatic.
+// These defines merely exist to do type-checking, force the void** cast & drop any const qualifier.
 /** Reallocate the given buffer from the given size by adding the delta size.
  * On success, the buffer size pointer will be updated to the buffer's new size
  * and the buffer pointer may be updated to a new memory address.
@@ -176,7 +176,7 @@ bool __mpw_free_string(
 bool __mpw_free_strings(
         char **strings, ...);
 void mpw_zero(
-        void *buffer, size_t bufferSize);
+        void *buffer, const size_t bufferSize);
 
 //// Cryptographic functions.
 
@@ -184,7 +184,7 @@ void mpw_zero(
  * @return A buffer (allocated, keySize) containing the key or NULL if secret or salt is missing, key could not be allocated or the KDF failed. */
 uint8_t const *mpw_kdf_scrypt(
         const size_t keySize, const uint8_t *secret, const size_t secretSize, const uint8_t *salt, const size_t saltSize,
-        uint64_t N, uint32_t r, uint32_t p);
+        const uint64_t N, const uint32_t r, const uint32_t p);
 /** Derive a subkey from the given key using the blake2b KDF.
  * @return A buffer (allocated, keySize) containing the key or NULL if the key or subkeySize is missing, the key sizes are out of bounds, the subkey could not be allocated or derived. */
 uint8_t const *mpw_kdf_blake2b(
@@ -217,11 +217,11 @@ const char *mpw_str(const char *format, ...);
 const char *mpw_vstr(const char *format, va_list args);
 /** Encode a buffer as a string of hexadecimal characters.
  * @return A string (shared); or NULL if the buffer is missing or the result could not be allocated. */
-const char *mpw_hex(const void *buf, size_t length);
-const char *mpw_hex_l(uint32_t number);
+const char *mpw_hex(const void *buf, const size_t length);
+const char *mpw_hex_l(const uint32_t number);
 /** Encode a fingerprint for a buffer.
  * @return A string (shared); or NULL if the buffer is missing or the result could not be allocated. */
-MPKeyID mpw_id_buf(const void *buf, size_t length);
+const MPKeyID mpw_id_buf(const void *buf, const size_t length);
 /** Compare two fingerprints for equality.
  * @return true if the buffers represent identical fingerprints or are both NULL. */
 bool mpw_id_buf_equals(const char *id1, const char *id2);
@@ -234,14 +234,14 @@ size_t mpw_utf8_charlen(const char *utf8String);
 size_t mpw_utf8_strchars(const char *utf8String);
 /** Drop-in for memdup(3).
  * @return A buffer (allocated, len) with len bytes copied from src or NULL if src is missing or the buffer could not be allocated. */
-void *mpw_memdup(const void *src, size_t len);
+void *mpw_memdup(const void *src, const size_t len);
 /** Drop-in for POSIX strdup(3).
  * @return A string (allocated) copied from src or NULL if src is missing or the buffer could not be allocated. */
 char *mpw_strdup(const char *src);
 /** Drop-in for POSIX strndup(3).
  * @return A string (allocated) with no more than max bytes copied from src or NULL if src is missing or the buffer could not be allocated. */
-char *mpw_strndup(const char *src, size_t max);
+char *mpw_strndup(const char *src, const size_t max);
 /** Drop-in for POSIX strncasecmp(3). */
-int mpw_strncasecmp(const char *s1, const char *s2, size_t max);
+int mpw_strncasecmp(const char *s1, const char *s2, const size_t max);
 
 #endif // _MPW_UTIL_H