diff --git a/docs/redirects.yaml b/docs/redirects.yaml
index 7ea1d95..969ffe4 100644
--- a/docs/redirects.yaml
+++ b/docs/redirects.yaml
@@ -7,5 +7,5 @@
 # expose it.
 
 - type: exact
-  from_url: /projects/api/en/latest/$rest
-  to_url: /projects/api/en/development/
+  from_url: /projects/api/en/latest/*
+  to_url: /projects/api/en/development/:splat
diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index a8baa6b..f17e14f 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -890,8 +890,9 @@
  * In case of a persistent key, the function loads the description of the key
  * into a key slot if not already done.
  *
- * On success, the returned key slot is locked. It is the responsibility of
- * the caller to unlock the key slot when it does not access it anymore.
+ * On success, the returned key slot has been registered for reading.
+ * It is the responsibility of the caller to call psa_unregister_read(slot)
+ * when they have finished reading the contents of the slot.
  */
 static psa_status_t psa_get_and_lock_key_slot_with_policy(
     mbedtls_svc_key_id_t key,
@@ -935,7 +936,7 @@
 
 error:
     *p_slot = NULL;
-    psa_unlock_key_slot(slot);
+    psa_unregister_read(slot);
 
     return status;
 }
@@ -950,8 +951,9 @@
  * psa_get_and_lock_key_slot_with_policy() when there is no opaque key support
  * for a cryptographic operation.
  *
- * On success, the returned key slot is locked. It is the responsibility of the
- * caller to unlock the key slot when it does not access it anymore.
+ * On success, the returned key slot has been registered for reading.
+ * It is the responsibility of the caller to call psa_unregister_read(slot)
+ * when they have finished reading the contents of the slot.
  */
 static psa_status_t psa_get_and_lock_transparent_key_slot_with_policy(
     mbedtls_svc_key_id_t key,
@@ -966,7 +968,7 @@
     }
 
     if (psa_key_lifetime_is_external((*p_slot)->attr.lifetime)) {
-        psa_unlock_key_slot(*p_slot);
+        psa_unregister_read(*p_slot);
         *p_slot = NULL;
         return PSA_ERROR_NOT_SUPPORTED;
     }
@@ -994,15 +996,41 @@
 
     /*
      * As the return error code may not be handled in case of multiple errors,
-     * do our best to report an unexpected lock counter. Assert with
-     * MBEDTLS_TEST_HOOK_TEST_ASSERT that the lock counter is equal to one:
+     * do our best to report an unexpected amount of registered readers or
+     * an unexpected state.
+     * Assert with MBEDTLS_TEST_HOOK_TEST_ASSERT that the slot is valid for
+     * wiping.
      * if the MBEDTLS_TEST_HOOKS configuration option is enabled and the
      * function is called as part of the execution of a test suite, the
      * execution of the test suite is stopped in error if the assertion fails.
      */
-    if (slot->lock_count != 1) {
-        MBEDTLS_TEST_HOOK_TEST_ASSERT(slot->lock_count == 1);
-        status = PSA_ERROR_CORRUPTION_DETECTED;
+    switch (slot->state) {
+        case PSA_SLOT_FULL:
+        /* In this state psa_wipe_key_slot() must only be called if the
+         * caller is the last reader. */
+        case PSA_SLOT_PENDING_DELETION:
+            /* In this state psa_wipe_key_slot() must only be called if the
+             * caller is the last reader. */
+            if (slot->registered_readers != 1) {
+                MBEDTLS_TEST_HOOK_TEST_ASSERT(slot->registered_readers == 1);
+                status = PSA_ERROR_CORRUPTION_DETECTED;
+            }
+            break;
+        case PSA_SLOT_FILLING:
+            /* In this state registered_readers must be 0. */
+            if (slot->registered_readers != 0) {
+                MBEDTLS_TEST_HOOK_TEST_ASSERT(slot->registered_readers == 0);
+                status = PSA_ERROR_CORRUPTION_DETECTED;
+            }
+            break;
+        case PSA_SLOT_EMPTY:
+            /* The slot is already empty, it cannot be wiped. */
+            MBEDTLS_TEST_HOOK_TEST_ASSERT(slot->state != PSA_SLOT_EMPTY);
+            status = PSA_ERROR_CORRUPTION_DETECTED;
+            break;
+        default:
+            /* The slot's state is invalid. */
+            status = PSA_ERROR_CORRUPTION_DETECTED;
     }
 
     /* Multipart operations may still be using the key. This is safe
@@ -1012,7 +1040,8 @@
      * key material can linger until all operations are completed. */
     /* At this point, key material and other type-specific content has
      * been wiped. Clear remaining metadata. We can call memset and not
-     * zeroize because the metadata is not particularly sensitive. */
+     * zeroize because the metadata is not particularly sensitive.
+     * This memset also sets the slot's state to PSA_SLOT_EMPTY. */
     memset(slot, 0, sizeof(*slot));
     return status;
 }
@@ -1031,28 +1060,26 @@
     }
 
     /*
-     * Get the description of the key in a key slot. In case of a persistent
-     * key, this will load the key description from persistent memory if not
-     * done yet. We cannot avoid this loading as without it we don't know if
+     * Get the description of the key in a key slot, and register to read it.
+     * In the case of a persistent key, this will load the key description
+     * from persistent memory if not done yet.
+     * We cannot avoid this loading as without it we don't know if
      * the key is operated by an SE or not and this information is needed by
-     * the current implementation.
-     */
+     * the current implementation. */
     status = psa_get_and_lock_key_slot(key, &slot);
     if (status != PSA_SUCCESS) {
         return status;
     }
 
-    /*
-     * If the key slot containing the key description is under access by the
-     * library (apart from the present access), the key cannot be destroyed
-     * yet. For the time being, just return in error. Eventually (to be
-     * implemented), the key should be destroyed when all accesses have
-     * stopped.
-     */
-    if (slot->lock_count > 1) {
-        psa_unlock_key_slot(slot);
-        return PSA_ERROR_GENERIC_ERROR;
-    }
+    /* Set the key slot containing the key description's state to
+     * PENDING_DELETION. This stops new operations from registering
+     * to read the slot. Current readers can safely continue to access
+     * the key within the slot; the last registered reader will
+     * automatically wipe the slot when they call psa_unregister_read().
+     * If the key is persistent, we can now delete the copy of the key
+     * from memory. If the key is opaque, we require the driver to
+     * deal with the deletion. */
+    slot->state = PSA_SLOT_PENDING_DELETION;
 
     if (PSA_KEY_LIFETIME_IS_READ_ONLY(slot->attr.lifetime)) {
         /* Refuse the destruction of a read-only key (which may or may not work
@@ -1100,6 +1127,9 @@
 
 #if defined(MBEDTLS_PSA_CRYPTO_STORAGE_C)
     if (!PSA_KEY_LIFETIME_IS_VOLATILE(slot->attr.lifetime)) {
+        /* Destroy the copy of the persistent key from storage.
+         * The slot will still hold a copy of the key until the last reader
+         * unregisters. */
         status = psa_destroy_persistent_key(slot->attr.id);
         if (overall_status == PSA_SUCCESS) {
             overall_status = status;
@@ -1126,8 +1156,11 @@
 #endif /* MBEDTLS_PSA_CRYPTO_SE_C */
 
 exit:
-    status = psa_wipe_key_slot(slot);
-    /* Prioritize CORRUPTION_DETECTED from wiping over a storage error */
+    /* Unregister from reading the slot. If we are the last active reader
+     * then this will wipe the slot. */
+    status = psa_unregister_read(slot);
+    /* Prioritize CORRUPTION_DETECTED from unregistering over
+     * a storage error. */
     if (status != PSA_SUCCESS) {
         overall_status = status;
     }
@@ -1252,7 +1285,7 @@
         psa_reset_key_attributes(attributes);
     }
 
-    unlock_status = psa_unlock_key_slot(slot);
+    unlock_status = psa_unregister_read(slot);
 
     return (status == PSA_SUCCESS) ? unlock_status : status;
 }
@@ -1348,7 +1381,7 @@
                                            slot->key.data, slot->key.bytes,
                                            data, data_size, data_length);
 
-    unlock_status = psa_unlock_key_slot(slot);
+    unlock_status = psa_unregister_read(slot);
 
     return (status == PSA_SUCCESS) ? unlock_status : status;
 }
@@ -1462,7 +1495,7 @@
         data, data_size, data_length);
 
 exit:
-    unlock_status = psa_unlock_key_slot(slot);
+    unlock_status = psa_unregister_read(slot);
 
     return (status == PSA_SUCCESS) ? unlock_status : status;
 }
@@ -1579,8 +1612,9 @@
  * In case of failure at any step, stop the sequence and call
  * psa_fail_key_creation().
  *
- * On success, the key slot is locked. It is the responsibility of the caller
- * to unlock the key slot when it does not access it anymore.
+ * On success, the key slot's state is PSA_SLOT_FILLING.
+ * It is the responsibility of the caller to change the slot's state to
+ * PSA_SLOT_EMPTY/FULL once key creation has finished.
  *
  * \param method            An identification of the calling function.
  * \param[in] attributes    Key attributes for the new key.
@@ -1611,7 +1645,7 @@
         return status;
     }
 
-    status = psa_get_empty_key_slot(&volatile_key_id, p_slot);
+    status = psa_reserve_free_key_slot(&volatile_key_id, p_slot);
     if (status != PSA_SUCCESS) {
         return status;
     }
@@ -1637,7 +1671,7 @@
     /* Erase external-only flags from the internal copy. To access
      * external-only flags, query `attributes`. Thanks to the check
      * in psa_validate_key_attributes(), this leaves the dual-use
-     * flags and any internal flag that psa_get_empty_key_slot()
+     * flags and any internal flag that psa_reserve_free_key_slot()
      * may have set. */
     slot->attr.flags &= ~MBEDTLS_PSA_KA_MASK_EXTERNAL_ONLY;
 
@@ -1689,8 +1723,6 @@
     }
 #endif /* MBEDTLS_PSA_CRYPTO_SE_C */
 
-    slot->status = PSA_SLOT_OCCUPIED;
-
     return PSA_SUCCESS;
 }
 
@@ -1702,9 +1734,9 @@
  * See the documentation of psa_start_key_creation() for the intended use
  * of this function.
  *
- * If the finalization succeeds, the function unlocks the key slot (it was
- * locked by psa_start_key_creation()) and the key slot cannot be accessed
- * anymore as part of the key creation process.
+ * If the finalization succeeds, the function sets the key slot's state to
+ * PSA_SLOT_FULL, and the key slot can no longer be accessed as part of the
+ * key creation process.
  *
  * \param[in,out] slot  Pointer to the slot with key material.
  * \param[in] driver    The secure element driver for the key,
@@ -1780,7 +1812,8 @@
 
     if (status == PSA_SUCCESS) {
         *key = slot->attr.id;
-        status = psa_unlock_key_slot(slot);
+        status = psa_key_slot_state_transition(slot, PSA_SLOT_FILLING,
+                                               PSA_SLOT_FULL);
         if (status != PSA_SUCCESS) {
             *key = MBEDTLS_SVC_KEY_ID_INIT;
         }
@@ -1795,7 +1828,7 @@
  * or after psa_finish_key_creation() fails. In other circumstances, this
  * function may not clean up persistent storage.
  * See the documentation of psa_start_key_creation() for the intended use
- * of this function.
+ * of this function. Sets the slot's state to PSA_SLOT_EMPTY.
  *
  * \param[in,out] slot  Pointer to the slot with key material.
  * \param[in] driver    The secure element driver for the key,
@@ -2134,7 +2167,7 @@
         psa_fail_key_creation(target_slot, driver);
     }
 
-    unlock_status = psa_unlock_key_slot(source_slot);
+    unlock_status = psa_unregister_read(source_slot);
 
     return (status == PSA_SUCCESS) ? unlock_status : status;
 }
@@ -2455,7 +2488,7 @@
         psa_mac_abort(operation);
     }
 
-    unlock_status = psa_unlock_key_slot(slot);
+    unlock_status = psa_unregister_read(slot);
 
     return (status == PSA_SUCCESS) ? unlock_status : status;
 }
@@ -2641,7 +2674,7 @@
 
     psa_wipe_tag_output_buffer(mac, status, mac_size, *mac_length);
 
-    unlock_status = psa_unlock_key_slot(slot);
+    unlock_status = psa_unregister_read(slot);
 
     return (status == PSA_SUCCESS) ? unlock_status : status;
 }
@@ -2785,7 +2818,7 @@
     psa_wipe_tag_output_buffer(signature, status, signature_size,
                                *signature_length);
 
-    unlock_status = psa_unlock_key_slot(slot);
+    unlock_status = psa_unregister_read(slot);
 
     return (status == PSA_SUCCESS) ? unlock_status : status;
 }
@@ -2833,7 +2866,7 @@
             signature, signature_length);
     }
 
-    unlock_status = psa_unlock_key_slot(slot);
+    unlock_status = psa_unregister_read(slot);
 
     return (status == PSA_SUCCESS) ? unlock_status : status;
 
@@ -3100,7 +3133,7 @@
         alg, input, input_length, salt, salt_length,
         output, output_size, output_length);
 exit:
-    unlock_status = psa_unlock_key_slot(slot);
+    unlock_status = psa_unregister_read(slot);
 
     return (status == PSA_SUCCESS) ? unlock_status : status;
 }
@@ -3152,7 +3185,7 @@
         output, output_size, output_length);
 
 exit:
-    unlock_status = psa_unlock_key_slot(slot);
+    unlock_status = psa_unregister_read(slot);
 
     return (status == PSA_SUCCESS) ? unlock_status : status;
 }
@@ -3261,7 +3294,7 @@
         psa_sign_hash_abort_internal(operation);
     }
 
-    unlock_status = psa_unlock_key_slot(slot);
+    unlock_status = psa_unregister_read(slot);
 
     if (unlock_status != PSA_SUCCESS) {
         operation->error_occurred = 1;
@@ -3406,7 +3439,7 @@
         psa_verify_hash_abort_internal(operation);
     }
 
-    unlock_status = psa_unlock_key_slot(slot);
+    unlock_status = psa_unregister_read(slot);
 
     if (unlock_status != PSA_SUCCESS) {
         operation->error_occurred = 1;
@@ -3978,7 +4011,7 @@
         psa_cipher_abort(operation);
     }
 
-    unlock_status = psa_unlock_key_slot(slot);
+    unlock_status = psa_unregister_read(slot);
 
     return (status == PSA_SUCCESS) ? unlock_status : status;
 }
@@ -4223,7 +4256,7 @@
         output_size - default_iv_length, output_length);
 
 exit:
-    unlock_status = psa_unlock_key_slot(slot);
+    unlock_status = psa_unregister_read(slot);
     if (status == PSA_SUCCESS) {
         status = unlock_status;
     }
@@ -4284,7 +4317,7 @@
         output, output_size, output_length);
 
 exit:
-    unlock_status = psa_unlock_key_slot(slot);
+    unlock_status = psa_unregister_read(slot);
     if (status == PSA_SUCCESS) {
         status = unlock_status;
     }
@@ -4410,7 +4443,7 @@
     }
 
 exit:
-    psa_unlock_key_slot(slot);
+    psa_unregister_read(slot);
 
     return status;
 }
@@ -4465,7 +4498,7 @@
     }
 
 exit:
-    psa_unlock_key_slot(slot);
+    psa_unregister_read(slot);
 
     return status;
 }
@@ -4577,7 +4610,7 @@
     operation->key_type = psa_get_key_type(&attributes);
 
 exit:
-    unlock_status = psa_unlock_key_slot(slot);
+    unlock_status = psa_unregister_read(slot);
 
     if (status == PSA_SUCCESS) {
         status = unlock_status;
@@ -6900,7 +6933,7 @@
                                                slot->key.data,
                                                slot->key.bytes);
 
-    unlock_status = psa_unlock_key_slot(slot);
+    unlock_status = psa_unregister_read(slot);
 
     return (status == PSA_SUCCESS) ? unlock_status : status;
 }
@@ -7057,7 +7090,7 @@
         }
     }
 
-    unlock_status = psa_unlock_key_slot(slot);
+    unlock_status = psa_unregister_read(slot);
 
     return (status == PSA_SUCCESS) ? unlock_status : status;
 }
@@ -7118,7 +7151,7 @@
         *output_length = output_size;
     }
 
-    unlock_status = psa_unlock_key_slot(slot);
+    unlock_status = psa_unregister_read(slot);
 
     return (status == PSA_SUCCESS) ? unlock_status : status;
 }
@@ -7792,7 +7825,7 @@
     if (status != PSA_SUCCESS) {
         psa_pake_abort(operation);
     }
-    unlock_status = psa_unlock_key_slot(slot);
+    unlock_status = psa_unregister_read(slot);
     return (status == PSA_SUCCESS) ? unlock_status : status;
 }
 
diff --git a/library/psa_crypto_core.h b/library/psa_crypto_core.h
index ff01add..1edd63e 100644
--- a/library/psa_crypto_core.h
+++ b/library/psa_crypto_core.h
@@ -47,8 +47,10 @@
 
 typedef enum {
     PSA_SLOT_EMPTY = 0,
-    PSA_SLOT_OCCUPIED,
-} psa_key_slot_status_t;
+    PSA_SLOT_FILLING,
+    PSA_SLOT_FULL,
+    PSA_SLOT_PENDING_DELETION,
+} psa_key_slot_state_t;
 
 /** The data structure representing a key slot, containing key material
  * and metadata for one key.
@@ -56,18 +58,37 @@
 typedef struct {
     psa_core_key_attributes_t attr;
 
-    psa_key_slot_status_t status;
+    /*
+     * The current state of the key slot, as described in
+     * docs/architecture/psa-thread-safety/psa-thread-safety.md.
+     *
+     * Library functions can modify the state of a key slot by calling
+     * psa_key_slot_state_transition.
+     *
+     * The state variable is used to help determine whether library functions
+     * which operate on the slot succeed. For example, psa_finish_key_creation,
+     * which transfers the state of a slot from PSA_SLOT_FILLING to
+     * PSA_SLOT_FULL, must fail with error code PSA_ERROR_CORRUPTION_DETECTED
+     * if the state of the slot is not PSA_SLOT_FILLING.
+     *
+     * Library functions which traverse the array of key slots only consider
+     * slots that are in a suitable state for the function.
+     * For example, psa_get_and_lock_key_slot_in_memory, which finds a slot
+     * containing a given key ID, will only check slots whose state variable is
+     * PSA_SLOT_FULL. */
+    psa_key_slot_state_t state;
 
     /*
-     * Number of locks on the key slot held by the library.
+     * Number of functions registered as reading the material in the key slot.
      *
-     * This counter is incremented by one each time a library function
-     * retrieves through one of the dedicated internal API a pointer to the
-     * key slot.
+     * Library functions must not write directly to registered_readers
      *
-     * This counter is decremented by one each time a library function stops
-     * accessing the key slot and states it by calling the
-     * psa_unlock_key_slot() API.
+     * A function must call psa_register_read(slot) before reading the current
+     * contents of the slot for an operation.
+     * They then must call psa_unregister_read(slot) once they have finished
+     * reading the current contents of the slot.
+     * A function must call psa_key_slot_has_readers(slot) to check if
+     * the slot is in use for reading.
      *
      * This counter is used to prevent resetting the key slot while the library
      * may access it. For example, such control is needed in the following
@@ -78,10 +99,9 @@
      *   the library cannot be reclaimed to free a key slot to load the
      *   persistent key.
      * . In case of a multi-threaded application where one thread asks to close
-     *   or purge or destroy a key while it is in used by the library through
-     *   another thread.
-     */
-    size_t lock_count;
+     *   or purge or destroy a key while it is in use by the library through
+     *   another thread. */
+    size_t registered_readers;
 
     /* Dynamically allocated key data buffer.
      * Format as specified in psa_export_key(). */
@@ -96,31 +116,15 @@
 #define PSA_KA_MASK_INTERNAL_ONLY (     \
         0)
 
-/** Test whether a key slot is occupied.
- *
- * A key slot is occupied iff the key type is nonzero. This works because
- * no valid key can have 0 as its key type.
+/** Test whether a key slot has any registered readers.
  *
  * \param[in] slot      The key slot to test.
  *
- * \return 1 if the slot is occupied, 0 otherwise.
+ * \return 1 if the slot has any registered readers, 0 otherwise.
  */
-static inline int psa_is_key_slot_occupied(const psa_key_slot_t *slot)
+static inline int psa_key_slot_has_readers(const psa_key_slot_t *slot)
 {
-    return slot->status == PSA_SLOT_OCCUPIED;
-}
-
-/** Test whether a key slot is locked.
- *
- * A key slot is locked iff its lock counter is strictly greater than 0.
- *
- * \param[in] slot  The key slot to test.
- *
- * \return 1 if the slot is locked, 0 otherwise.
- */
-static inline int psa_is_key_slot_locked(const psa_key_slot_t *slot)
-{
-    return slot->lock_count > 0;
+    return slot->registered_readers > 0;
 }
 
 /** Retrieve flags from psa_key_slot_t::attr::core::flags.
@@ -190,13 +194,18 @@
 /** Completely wipe a slot in memory, including its policy.
  *
  * Persistent storage is not affected.
+ * Sets the slot's state to PSA_SLOT_EMPTY.
  *
  * \param[in,out] slot  The key slot to wipe.
  *
  * \retval #PSA_SUCCESS
- *         Success. This includes the case of a key slot that was
- *         already fully wiped.
- * \retval #PSA_ERROR_CORRUPTION_DETECTED \emptydescription
+ *         The slot has been successfully wiped.
+ * \retval #PSA_ERROR_CORRUPTION_DETECTED
+ *         The slot's state was PSA_SLOT_FULL or PSA_SLOT_PENDING_DELETION, and
+ *         the amount of registered readers was not equal to 1. Or,
+ *         the slot's state was PSA_SLOT_EMPTY. Or,
+ *         the slot's state was PSA_SLOT_FILLING, and the amount
+ *         of registered readers was not equal to 0.
  */
 psa_status_t psa_wipe_key_slot(psa_key_slot_t *slot);
 
diff --git a/library/psa_crypto_slot_management.c b/library/psa_crypto_slot_management.c
index 5ecc3a7..8d7ff90 100644
--- a/library/psa_crypto_slot_management.c
+++ b/library/psa_crypto_slot_management.c
@@ -108,7 +108,9 @@
 
         for (slot_idx = 0; slot_idx < MBEDTLS_PSA_KEY_SLOT_COUNT; slot_idx++) {
             slot = &global_data.key_slots[slot_idx];
-            if (mbedtls_svc_key_id_equal(key, slot->attr.id)) {
+            /* Only consider slots which are in a full state. */
+            if ((slot->state == PSA_SLOT_FULL) &&
+                (mbedtls_svc_key_id_equal(key, slot->attr.id))) {
                 break;
             }
         }
@@ -117,7 +119,7 @@
     }
 
     if (status == PSA_SUCCESS) {
-        status = psa_lock_key_slot(slot);
+        status = psa_register_read(slot);
         if (status == PSA_SUCCESS) {
             *p_slot = slot;
         }
@@ -141,36 +143,38 @@
 
     for (slot_idx = 0; slot_idx < MBEDTLS_PSA_KEY_SLOT_COUNT; slot_idx++) {
         psa_key_slot_t *slot = &global_data.key_slots[slot_idx];
-        slot->lock_count = 1;
+        slot->registered_readers = 1;
+        slot->state = PSA_SLOT_PENDING_DELETION;
         (void) psa_wipe_key_slot(slot);
     }
     global_data.key_slots_initialized = 0;
 }
 
-psa_status_t psa_get_empty_key_slot(psa_key_id_t *volatile_key_id,
-                                    psa_key_slot_t **p_slot)
+psa_status_t psa_reserve_free_key_slot(psa_key_id_t *volatile_key_id,
+                                       psa_key_slot_t **p_slot)
 {
     psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
     size_t slot_idx;
-    psa_key_slot_t *selected_slot, *unlocked_persistent_key_slot;
+    psa_key_slot_t *selected_slot, *unused_persistent_key_slot;
 
     if (!global_data.key_slots_initialized) {
         status = PSA_ERROR_BAD_STATE;
         goto error;
     }
 
-    selected_slot = unlocked_persistent_key_slot = NULL;
+    selected_slot = unused_persistent_key_slot = NULL;
     for (slot_idx = 0; slot_idx < MBEDTLS_PSA_KEY_SLOT_COUNT; slot_idx++) {
         psa_key_slot_t *slot = &global_data.key_slots[slot_idx];
-        if (!psa_is_key_slot_occupied(slot)) {
+        if (slot->state == PSA_SLOT_EMPTY) {
             selected_slot = slot;
             break;
         }
 
-        if ((unlocked_persistent_key_slot == NULL) &&
-            (!PSA_KEY_LIFETIME_IS_VOLATILE(slot->attr.lifetime)) &&
-            (!psa_is_key_slot_locked(slot))) {
-            unlocked_persistent_key_slot = slot;
+        if ((unused_persistent_key_slot == NULL) &&
+            (slot->state == PSA_SLOT_FULL) &&
+            (!psa_key_slot_has_readers(slot)) &&
+            (!PSA_KEY_LIFETIME_IS_VOLATILE(slot->attr.lifetime))) {
+            unused_persistent_key_slot = slot;
         }
     }
 
@@ -182,14 +186,18 @@
      * storage.
      */
     if ((selected_slot == NULL) &&
-        (unlocked_persistent_key_slot != NULL)) {
-        selected_slot = unlocked_persistent_key_slot;
-        selected_slot->lock_count = 1;
-        psa_wipe_key_slot(selected_slot);
+        (unused_persistent_key_slot != NULL)) {
+        selected_slot = unused_persistent_key_slot;
+        psa_register_read(selected_slot);
+        status = psa_wipe_key_slot(selected_slot);
+        if (status != PSA_SUCCESS) {
+            goto error;
+        }
     }
 
     if (selected_slot != NULL) {
-        status = psa_lock_key_slot(selected_slot);
+        status = psa_key_slot_state_transition(selected_slot, PSA_SLOT_EMPTY,
+                                               PSA_SLOT_FILLING);
         if (status != PSA_SUCCESS) {
             goto error;
         }
@@ -239,7 +247,8 @@
             slot, data->slot_number, sizeof(data->slot_number));
 
         if (status == PSA_SUCCESS) {
-            slot->status = PSA_SLOT_OCCUPIED;
+            status = psa_key_slot_state_transition(slot, PSA_SLOT_FILLING,
+                                                   PSA_SLOT_FULL);
         }
         goto exit;
     }
@@ -250,7 +259,8 @@
         goto exit;
     }
 
-    slot->status = PSA_SLOT_OCCUPIED;
+    status = psa_key_slot_state_transition(slot, PSA_SLOT_FILLING,
+                                           PSA_SLOT_FULL);
 
 exit:
     psa_free_persistent_key_data(key_data, key_data_length);
@@ -324,8 +334,9 @@
     /* Copy actual key length and core attributes into the slot on success */
     slot->key.bytes = key_buffer_length;
     slot->attr = attributes.core;
-    slot->status = PSA_SLOT_OCCUPIED;
 
+    status = psa_key_slot_state_transition(slot, PSA_SLOT_FILLING,
+                                           PSA_SLOT_FULL);
 exit:
     if (status != PSA_SUCCESS) {
         psa_remove_key_data_from_memory(slot);
@@ -358,7 +369,7 @@
     defined(MBEDTLS_PSA_CRYPTO_BUILTIN_KEYS)
     psa_key_id_t volatile_key_id;
 
-    status = psa_get_empty_key_slot(&volatile_key_id, p_slot);
+    status = psa_reserve_free_key_slot(&volatile_key_id, p_slot);
     if (status != PSA_SUCCESS) {
         return status;
     }
@@ -380,12 +391,17 @@
 
     if (status != PSA_SUCCESS) {
         psa_wipe_key_slot(*p_slot);
+
         if (status == PSA_ERROR_DOES_NOT_EXIST) {
             status = PSA_ERROR_INVALID_HANDLE;
         }
     } else {
         /* Add implicit usage flags. */
         psa_extend_key_usage_flags(&(*p_slot)->attr.policy.usage);
+
+        psa_key_slot_state_transition((*p_slot), PSA_SLOT_FILLING,
+                                      PSA_SLOT_FULL);
+        status = psa_register_read(*p_slot);
     }
 
     return status;
@@ -394,26 +410,37 @@
 #endif /* MBEDTLS_PSA_CRYPTO_STORAGE_C || MBEDTLS_PSA_CRYPTO_BUILTIN_KEYS */
 }
 
-psa_status_t psa_unlock_key_slot(psa_key_slot_t *slot)
+psa_status_t psa_unregister_read(psa_key_slot_t *slot)
 {
     if (slot == NULL) {
         return PSA_SUCCESS;
     }
+    if ((slot->state != PSA_SLOT_FULL) &&
+        (slot->state != PSA_SLOT_PENDING_DELETION)) {
+        return PSA_ERROR_CORRUPTION_DETECTED;
+    }
 
-    if (slot->lock_count > 0) {
-        slot->lock_count--;
+    /* If we are the last reader and the slot is marked for deletion,
+     * we must wipe the slot here. */
+    if ((slot->state == PSA_SLOT_PENDING_DELETION) &&
+        (slot->registered_readers == 1)) {
+        return psa_wipe_key_slot(slot);
+    }
+
+    if (psa_key_slot_has_readers(slot)) {
+        slot->registered_readers--;
         return PSA_SUCCESS;
     }
 
     /*
      * As the return error code may not be handled in case of multiple errors,
-     * do our best to report if the lock counter is equal to zero. Assert with
-     * MBEDTLS_TEST_HOOK_TEST_ASSERT that the lock counter is strictly greater
-     * than zero: if the MBEDTLS_TEST_HOOKS configuration option is enabled and
+     * do our best to report if there are no registered readers. Assert with
+     * MBEDTLS_TEST_HOOK_TEST_ASSERT that there are registered readers:
+     * if the MBEDTLS_TEST_HOOKS configuration option is enabled and
      * the function is called as part of the execution of a test suite, the
      * execution of the test suite is stopped in error if the assertion fails.
      */
-    MBEDTLS_TEST_HOOK_TEST_ASSERT(slot->lock_count > 0);
+    MBEDTLS_TEST_HOOK_TEST_ASSERT(psa_key_slot_has_readers(slot));
     return PSA_ERROR_CORRUPTION_DETECTED;
 }
 
@@ -480,7 +507,7 @@
 
     *handle = key;
 
-    return psa_unlock_key_slot(slot);
+    return psa_unregister_read(slot);
 
 #else /* MBEDTLS_PSA_CRYPTO_STORAGE_C || MBEDTLS_PSA_CRYPTO_BUILTIN_KEYS */
     (void) key;
@@ -506,10 +533,10 @@
 
         return status;
     }
-    if (slot->lock_count <= 1) {
+    if (slot->registered_readers == 1) {
         return psa_wipe_key_slot(slot);
     } else {
-        return psa_unlock_key_slot(slot);
+        return psa_unregister_read(slot);
     }
 }
 
@@ -524,10 +551,10 @@
     }
 
     if ((!PSA_KEY_LIFETIME_IS_VOLATILE(slot->attr.lifetime)) &&
-        (slot->lock_count <= 1)) {
+        (slot->registered_readers == 1)) {
         return psa_wipe_key_slot(slot);
     } else {
-        return psa_unlock_key_slot(slot);
+        return psa_unregister_read(slot);
     }
 }
 
@@ -539,10 +566,10 @@
 
     for (slot_idx = 0; slot_idx < MBEDTLS_PSA_KEY_SLOT_COUNT; slot_idx++) {
         const psa_key_slot_t *slot = &global_data.key_slots[slot_idx];
-        if (psa_is_key_slot_locked(slot)) {
+        if (psa_key_slot_has_readers(slot)) {
             ++stats->locked_slots;
         }
-        if (!psa_is_key_slot_occupied(slot)) {
+        if (slot->state == PSA_SLOT_EMPTY) {
             ++stats->empty_slots;
             continue;
         }
diff --git a/library/psa_crypto_slot_management.h b/library/psa_crypto_slot_management.h
index 6041a35..0b0d7b3 100644
--- a/library/psa_crypto_slot_management.h
+++ b/library/psa_crypto_slot_management.h
@@ -54,8 +54,9 @@
  * In case of a persistent key, the function loads the description of the key
  * into a key slot if not already done.
  *
- * On success, the returned key slot is locked. It is the responsibility of
- * the caller to unlock the key slot when it does not access it anymore.
+ * On success, the returned key slot has been registered for reading.
+ * It is the responsibility of the caller to call psa_unregister_read(slot)
+ * when they have finished reading the contents of the slot.
  *
  * \param key           Key identifier to query.
  * \param[out] p_slot   On success, `*p_slot` contains a pointer to the
@@ -95,50 +96,85 @@
  * This does not affect persistent storage. */
 void psa_wipe_all_key_slots(void);
 
-/** Find a free key slot.
+/** Find a free key slot and reserve it to be filled with a key.
  *
- * This function returns a key slot that is available for use and is in its
- * ground state (all-bits-zero). On success, the key slot is locked. It is
- * the responsibility of the caller to unlock the key slot when it does not
- * access it anymore.
+ * This function finds a key slot that is free,
+ * sets its state to PSA_SLOT_FILLING and then returns the slot.
+ *
+ * On success, the key slot's state is PSA_SLOT_FILLING.
+ * It is the responsibility of the caller to change the slot's state to
+ * PSA_SLOT_EMPTY/FULL once key creation has finished.
  *
  * \param[out] volatile_key_id   On success, volatile key identifier
  *                               associated to the returned slot.
  * \param[out] p_slot            On success, a pointer to the slot.
  *
  * \retval #PSA_SUCCESS \emptydescription
- * \retval #PSA_ERROR_INSUFFICIENT_MEMORY \emptydescription
+ * \retval #PSA_ERROR_INSUFFICIENT_MEMORY
+ *         There were no free key slots.
  * \retval #PSA_ERROR_BAD_STATE \emptydescription
+ * \retval #PSA_ERROR_CORRUPTION_DETECTED
+ *         This function attempted to operate on a key slot which was in an
+ *         unexpected state.
  */
-psa_status_t psa_get_empty_key_slot(psa_key_id_t *volatile_key_id,
-                                    psa_key_slot_t **p_slot);
+psa_status_t psa_reserve_free_key_slot(psa_key_id_t *volatile_key_id,
+                                       psa_key_slot_t **p_slot);
 
-/** Lock a key slot.
+/** Change the state of a key slot.
  *
- * This function increments the key slot lock counter by one.
+ * This function changes the state of the key slot from expected_state to
+ * new state. If the state of the slot was not expected_state, the state is
+ * unchanged.
+ *
+ * \param[in] slot            The key slot.
+ * \param[in] expected_state  The current state of the slot.
+ * \param[in] new_state       The new state of the slot.
+ *
+ * \retval #PSA_SUCCESS
+               The key slot's state variable is new_state.
+ * \retval #PSA_ERROR_CORRUPTION_DETECTED
+ *             The slot's state was not expected_state.
+ */
+static inline psa_status_t psa_key_slot_state_transition(
+    psa_key_slot_t *slot, psa_key_slot_state_t expected_state,
+    psa_key_slot_state_t new_state)
+{
+    if (slot->state != expected_state) {
+        return PSA_ERROR_CORRUPTION_DETECTED;
+    }
+    slot->state = new_state;
+    return PSA_SUCCESS;
+}
+
+/** Register as a reader of a key slot.
+ *
+ * This function increments the key slot registered reader counter by one.
  *
  * \param[in] slot  The key slot.
  *
  * \retval #PSA_SUCCESS
-               The key slot lock counter was incremented.
+               The key slot registered reader counter was incremented.
  * \retval #PSA_ERROR_CORRUPTION_DETECTED
- *             The lock counter already reached its maximum value and was not
- *             increased.
+ *             The reader counter already reached its maximum value and was not
+ *             increased, or the slot's state was not PSA_SLOT_FULL.
  */
-static inline psa_status_t psa_lock_key_slot(psa_key_slot_t *slot)
+static inline psa_status_t psa_register_read(psa_key_slot_t *slot)
 {
-    if (slot->lock_count >= SIZE_MAX) {
+    if ((slot->state != PSA_SLOT_FULL) ||
+        (slot->registered_readers >= SIZE_MAX)) {
         return PSA_ERROR_CORRUPTION_DETECTED;
     }
-
-    slot->lock_count++;
+    slot->registered_readers++;
 
     return PSA_SUCCESS;
 }
 
-/** Unlock a key slot.
+/** Unregister from reading a key slot.
  *
- * This function decrements the key slot lock counter by one.
+ * This function decrements the key slot registered reader counter by one.
+ * If the state of the slot is PSA_SLOT_PENDING_DELETION,
+ * and there is only one registered reader (the caller),
+ * this function will call psa_wipe_key_slot().
  *
  * \note To ease the handling of errors in retrieving a key slot
  *       a NULL input pointer is valid, and the function returns
@@ -146,13 +182,16 @@
  *
  * \param[in] slot  The key slot.
  * \retval #PSA_SUCCESS
- *             \p slot is NULL or the key slot lock counter has been
- *             decremented successfully.
+ *             \p slot is NULL or the key slot reader counter has been
+ *             decremented (and potentially wiped) successfully.
  * \retval #PSA_ERROR_CORRUPTION_DETECTED
- *             The lock counter was equal to 0.
- *
+ *             The slot's state was neither PSA_SLOT_FULL nor
+ *             PSA_SLOT_PENDING_DELETION.
+ *             Or a wipe was attempted and the slot's state was not
+ *             PSA_SLOT_PENDING_DELETION.
+ *             Or registered_readers was equal to 0.
  */
-psa_status_t psa_unlock_key_slot(psa_key_slot_t *slot);
+psa_status_t psa_unregister_read(psa_key_slot_t *slot);
 
 /** Test whether a lifetime designates a key in an external cryptoprocessor.
  *