diff --git a/library/ssl_tls13_keys.c b/library/ssl_tls13_keys.c
index f1c8a12..2831313 100644
--- a/library/ssl_tls13_keys.c
+++ b/library/ssl_tls13_keys.c
@@ -699,4 +699,112 @@
     return( ret );
 }
 
+int mbedtls_ssl_tls13_populate_transform( mbedtls_ssl_transform *transform,
+                                          int endpoint,
+                                          int ciphersuite,
+                                          mbedtls_ssl_key_set const *traffic_keys,
+                                          mbedtls_ssl_context *ssl /* DEBUG ONLY */ )
+{
+    int ret;
+    mbedtls_cipher_info_t const *cipher_info;
+    const mbedtls_ssl_ciphersuite_t *ciphersuite_info;
+    unsigned char const *key_enc;
+    unsigned char const *iv_enc;
+    unsigned char const *key_dec;
+    unsigned char const *iv_dec;
+
+#if !defined(MBEDTLS_DEBUG_C)
+    ssl = NULL; /* make sure we don't use it except for those cases */
+    (void) ssl;
+#endif
+
+    ciphersuite_info = mbedtls_ssl_ciphersuite_from_id( ciphersuite );
+
+    cipher_info = mbedtls_cipher_info_from_type( ciphersuite_info->cipher );
+    if( cipher_info == NULL )
+    {
+        MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+    }
+
+    /*
+     * Setup cipher contexts in target transform
+     */
+
+    if( ( ret = mbedtls_cipher_setup( &transform->cipher_ctx_enc,
+                                      cipher_info ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_setup", ret );
+        return( ret );
+    }
+
+    if( ( ret = mbedtls_cipher_setup( &transform->cipher_ctx_dec,
+                                      cipher_info ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_setup", ret );
+        return( ret );
+    }
+
+#if defined(MBEDTLS_SSL_SRV_C)
+    if( endpoint == MBEDTLS_SSL_IS_SERVER )
+    {
+        key_enc = traffic_keys->server_write_key;
+        key_dec = traffic_keys->client_write_key;
+        iv_enc = traffic_keys->server_write_iv;
+        iv_dec = traffic_keys->client_write_iv;
+    }
+    else
+#endif /* MBEDTLS_SSL_SRV_C */
+#if defined(MBEDTLS_SSL_CLI_C)
+    if( endpoint == MBEDTLS_SSL_IS_CLIENT )
+    {
+        key_enc = traffic_keys->client_write_key;
+        key_dec = traffic_keys->server_write_key;
+        iv_enc = traffic_keys->client_write_iv;
+        iv_dec = traffic_keys->server_write_iv;
+    }
+    else
+#endif /* MBEDTLS_SSL_CLI_C */
+    {
+        /* should not happen */
+        return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+    }
+
+    memcpy( transform->iv_enc, iv_enc, traffic_keys->iv_len );
+    memcpy( transform->iv_dec, iv_dec, traffic_keys->iv_len );
+
+    if( ( ret = mbedtls_cipher_setkey( &transform->cipher_ctx_enc,
+                                       key_enc, cipher_info->key_bitlen,
+                                       MBEDTLS_ENCRYPT ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_setkey", ret );
+        return( ret );
+    }
+
+    if( ( ret = mbedtls_cipher_setkey( &transform->cipher_ctx_dec,
+                                       key_dec, cipher_info->key_bitlen,
+                                       MBEDTLS_DECRYPT ) ) != 0 )
+    {
+        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_cipher_setkey", ret );
+        return( ret );
+    }
+
+    /*
+     * Setup other fields in SSL transform
+     */
+
+    if( ( ciphersuite_info->flags & MBEDTLS_CIPHERSUITE_SHORT_TAG ) != 0 )
+        transform->taglen  = 8;
+    else
+        transform->taglen  = 16;
+
+    transform->ivlen       = traffic_keys->iv_len;
+    transform->maclen      = 0;
+    transform->fixed_ivlen = transform->ivlen;
+    transform->minlen      = transform->taglen + 1;
+    transform->minor_ver   = MBEDTLS_SSL_MINOR_VERSION_4;
+
+    return( 0 );
+}
+
 #endif /* MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL */
diff --git a/library/ssl_tls13_keys.h b/library/ssl_tls13_keys.h
index 3b96998..ca892b1 100644
--- a/library/ssl_tls13_keys.h
+++ b/library/ssl_tls13_keys.h
@@ -498,4 +498,37 @@
                                unsigned char const *transcript,
                                unsigned char *result );
 
+/**
+ * \bref Setup an SSL transform structure representing the
+ *       record protection mechanism used by TLS 1.3
+ *
+ * \param transform    The SSL transform structure to be created. This must have
+ *                     been initialized through mbedtls_ssl_transform_init() and
+ *                     not used in any other way prior to calling this function.
+ *                     In particular, this function does not clean up the
+ *                     transform structure prior to installing the new keys.
+ * \param endpoint     Indicates whether the transform is for the client
+ *                     (value #MBEDTLS_SSL_IS_CLIENT) or the server
+ *                     (value #MBEDTLS_SSL_IS_SERVER).
+ * \param ciphersuite  The numerical identifier for the ciphersuite to use.
+ *                     This must be one of the identifiers listed in
+ *                     ssl_ciphersuites.h.
+ * \param traffic_keys The key material to use. No reference is stored in
+ *                     the SSL transform being generated, and the caller
+ *                     should destroy the key material afterwards.
+ * \param ssl          (Debug-only) The SSL context to use for debug output
+ *                     in case of failure. This parameter is only needed if
+ *                     #MBEDTLS_DEBUG_C is set, and is ignored otherwise.
+ *
+ * \return             \c 0 on success. In this case, \p transform is ready to
+ *                     be used with mbedtls_ssl_transform_decrypt() and
+ *                     mbedtls_ssl_transform_encrypt().
+ * \return             A negative error code on failure.
+ */
+int mbedtls_ssl_tls13_populate_transform( mbedtls_ssl_transform *transform,
+                                          int endpoint,
+                                          int ciphersuite,
+                                          mbedtls_ssl_key_set const *traffic_keys,
+                                          mbedtls_ssl_context *ssl );
+
 #endif /* MBEDTLS_SSL_TLS1_3_KEYS_H */