diff --git a/library/psa_crypto_storage.c b/library/psa_crypto_storage.c
index cd36bb9..d07bdc5 100644
--- a/library/psa_crypto_storage.c
+++ b/library/psa_crypto_storage.c
@@ -50,6 +50,12 @@
 #define mbedtls_free     free
 #endif
 
+
+
+/****************************************************************/
+/* Key storage */
+/****************************************************************/
+
 /* Determine a file name (ITS file identifier) for the given key file
  * identifier. The file name must be distinct from any file that is used
  * for a purpose other than storing a key. Currently, the only such file
@@ -399,6 +405,60 @@
     return( status );
 }
 
+
+
+/****************************************************************/
+/* Transactions */
+/****************************************************************/
+
+#if defined(PSA_CRYPTO_STORAGE_HAS_TRANSACTIONS)
+
+psa_crypto_transaction_t psa_crypto_transaction;
+
+psa_status_t psa_crypto_save_transaction( void )
+{
+    struct psa_storage_info_t p_info;
+    psa_status_t status;
+    status = psa_its_get_info( PSA_CRYPTO_ITS_RANDOM_SEED_UID, &p_info );
+    if( status == PSA_SUCCESS )
+    {
+        /* This shouldn't happen: we're trying to start a transaction while
+         * there is still a transaction that hasn't been replayed. */
+        return( PSA_ERROR_CORRUPTION_DETECTED );
+    }
+    else if( status != PSA_ERROR_DOES_NOT_EXIST )
+        return( status );
+    return( psa_its_set( PSA_CRYPTO_ITS_TRANSACTION_UID,
+                         sizeof( psa_crypto_transaction ),
+                         &psa_crypto_transaction,
+                         0 ) );
+}
+
+psa_status_t psa_crypto_load_transaction( void )
+{
+    return( psa_its_get( PSA_CRYPTO_ITS_TRANSACTION_UID, 0,
+                         sizeof( psa_crypto_transaction ),
+                         &psa_crypto_transaction ) );
+}
+
+psa_status_t psa_crypto_stop_transaction( void )
+{
+    psa_status_t status = psa_its_remove( PSA_CRYPTO_ITS_TRANSACTION_UID );
+    /* Whether or not updating the storage succeeded, the transaction is
+     * finished now. It's too late to go back, so zero out the in-memory
+     * data. */
+    memset( &psa_crypto_transaction, 0, sizeof( psa_crypto_transaction ) );
+    return( status );
+}
+
+#endif /* PSA_CRYPTO_STORAGE_HAS_TRANSACTIONS */
+
+
+
+/****************************************************************/
+/* Random generator state */
+/****************************************************************/
+
 #if defined(MBEDTLS_PSA_INJECT_ENTROPY)
 psa_status_t mbedtls_psa_storage_inject_entropy( const unsigned char *seed,
                                                  size_t seed_size )
@@ -421,4 +481,10 @@
 }
 #endif /* MBEDTLS_PSA_INJECT_ENTROPY */
 
+
+
+/****************************************************************/
+/* The end */
+/****************************************************************/
+
 #endif /* MBEDTLS_PSA_CRYPTO_STORAGE_C */
diff --git a/library/psa_crypto_storage.h b/library/psa_crypto_storage.h
index 2af624a..16f5d5c 100644
--- a/library/psa_crypto_storage.h
+++ b/library/psa_crypto_storage.h
@@ -39,6 +39,7 @@
 
 #include "psa/crypto.h"
 #include <stdint.h>
+#include <string.h>
 
 /* Limit the maximum key size to 30kB (just in case someone tries to
  * inadvertently store an obscene amount of data) */
@@ -203,6 +204,138 @@
                                               psa_key_type_t *type,
                                               psa_key_policy_t *policy );
 
+#if defined(MBEDTLS_PSA_CRYPTO_SE_C)
+/** This symbol is defined if transaction support is required. */
+#define PSA_CRYPTO_STORAGE_HAS_TRANSACTIONS
+#endif
+
+#if defined(PSA_CRYPTO_STORAGE_HAS_TRANSACTIONS)
+
+/** The type of transaction that is in progress.
+ */
+/* This is an integer type rather than an enum for two reasons: to support
+ * unknown values when loading a transaction file, and to ensure that the
+ * type has a known size.
+ */
+typedef uint16_t psa_crypto_transaction_type_t;
+
+/** No transaction is in progress.
+ */
+#define PSA_CRYPTO_TRANSACTION_NONE             ( (psa_crypto_transaction_type_t) 0x0000 )
+
+/** Transaction data.
+ *
+ * This type is designed to be serialized by writing the memory representation
+ * and reading it back on the same device.
+ *
+ * \note The transaction mechanism is designed for a single active transaction
+ *       at a time. The transaction object is #psa_crypto_transaction.
+ *
+ * \note If an API call starts a transaction, it must complete this transaction
+ *       before returning to the application.
+ *
+ * The lifetime of a transaction is the following (note that only one
+ * transaction may be active at a time):
+ *
+ * -# Call psa_crypto_prepare_transaction() to initialize the transaction
+ *    object in memory and declare the type of transaction that is starting.
+ * -# Fill in the type-specific fields of #psa_crypto_transaction.
+ * -# Call psa_crypto_save_transaction() to start the transaction. This
+ *    saves the transaction data to internal storage.
+ * -# If there are intermediate stages in the transaction, update
+ *    the fields of #psa_crypto_transaction and call
+ *    psa_crypto_save_transaction() again when each stage is reached.
+ * -# When the transaction is over, whether it has been committed or aborted,
+ *    call psa_crypto_stop_transaction() to remove the transaction data in
+ *    storage and in memory.
+ *
+ * If the system crashes while a transaction is in progress, psa_crypto_init()
+ * calls psa_crypto_load_transaction() and takes care of completing or
+ * rewinding the transaction.
+ */
+typedef union
+{
+    /* Each element of this union must have the following properties
+     * to facilitate serialization and deserialization:
+     *
+     * - The element is a struct.
+     * - The first field of the struct is `psa_crypto_transaction_type_t type`.
+     * - Elements of the struct are arranged such a way that there is
+     *   no padding.
+     */
+    struct psa_crypto_transaction_unknown_s
+    {
+        psa_crypto_transaction_type_t type;
+    } unknown;
+} psa_crypto_transaction_t;
+
+/** The single active transaction.
+ */
+extern psa_crypto_transaction_t psa_crypto_transaction;
+
+/** Prepare for a transaction.
+ *
+ * There must not be an ongoing transaction.
+ *
+ * \param type          The type of transaction to start.
+ */
+static inline void psa_crypto_prepare_transaction(
+    psa_crypto_transaction_type_t type )
+{
+    psa_crypto_transaction.unknown.type = type;
+}
+
+/** Save the transaction data to storage.
+ *
+ * You may call this function multiple times during a transaction to
+ * atomically update the transaction state.
+ *
+ * \retval #PSA_SUCCESS
+ * \retval #PSA_ERROR_INSUFFICIENT_STORAGE
+ * \retval #PSA_ERROR_STORAGE_FAILURE
+ */
+psa_status_t psa_crypto_save_transaction( void );
+
+/** Load the transaction data from storage, if any.
+ *
+ * This function is meant to be called from psa_crypto_init() to recover
+ * in case a transaction was interrupted by a system crash.
+ *
+ * \retval #PSA_SUCCESS
+ *         The data about the ongoing transaction has been loaded to
+ *         #psa_crypto_transaction.
+ * \retval #PSA_ERROR_DOES_NOT_EXIST
+ *         There is no ongoing transaction.
+ * \retval #PSA_ERROR_STORAGE_FAILURE
+ */
+psa_status_t psa_crypto_load_transaction( void );
+
+/** Indicate that the current transaction is finished.
+ *
+ * Call this function at the very end of transaction processing, whether
+ * the transaction has been committed or aborted.
+ *
+ * This function erases the transaction data in storage (if any) and
+ * resets the transaction data in memory.
+ *
+ * \retval #PSA_SUCCESS
+ *         There was transaction data in storage.
+ * \retval #PSA_ERROR_DOES_NOT_EXIST
+ *         There was no transaction data in storage.
+ * \retval #PSA_ERROR_STORAGE_FAILURE
+ *         It was impossible to determine whether there was transaction data
+ *         in storage, or the transaction data could not be erased.
+ */
+psa_status_t psa_crypto_stop_transaction( void );
+
+/** The ITS file identifier for the transaction data.
+ *
+ * 0xffffffNN = special file; 0x74 = 't' for transaction.
+ */
+#define PSA_CRYPTO_ITS_TRANSACTION_UID ( (psa_key_id_t) 0xffffff74 )
+
+#endif /* PSA_CRYPTO_STORAGE_HAS_TRANSACTIONS */
+
 #if defined(MBEDTLS_PSA_INJECT_ENTROPY)
 /** Backend side of mbedtls_psa_inject_entropy().
  *