diff --git a/include/lib/psa/measured_boot.h b/include/lib/psa/measured_boot.h
new file mode 100644
index 0000000..bdb79d5
--- /dev/null
+++ b/include/lib/psa/measured_boot.h
@@ -0,0 +1,77 @@
+/*
+ * Copyright (c) 2022, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ */
+
+#ifndef PSA_MEASURED_BOOT_H
+#define PSA_MEASURED_BOOT_H
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#include "psa/error.h"
+
+/* Minimum measurement value size that can be requested to store */
+#define MEASUREMENT_VALUE_MIN_SIZE	32U
+/* Maximum measurement value size that can be requested to store */
+#define MEASUREMENT_VALUE_MAX_SIZE	64U
+/* Minimum signer id size that can be requested to store */
+#define SIGNER_ID_MIN_SIZE		MEASUREMENT_VALUE_MIN_SIZE
+/* Maximum signer id size that can be requested to store */
+#define SIGNER_ID_MAX_SIZE		MEASUREMENT_VALUE_MAX_SIZE
+/* The theoretical maximum image version is: "255.255.65535\0" */
+#define VERSION_MAX_SIZE		14U
+/* Example sw_type: "BL_2, BL_33, etc." */
+#define SW_TYPE_MAX_SIZE		20U
+#define NUM_OF_MEASUREMENT_SLOTS	32U
+
+
+/**
+ * Extends and stores a measurement to the requested slot.
+ *
+ * index			Slot number in which measurement is to be stored
+ * signer_id			Pointer to signer_id buffer.
+ * signer_id_size		Size of the signer_id buffer in bytes.
+ * version			Pointer to version buffer.
+ * version_size			Size of the version buffer in bytes.
+ * measurement_algo		Algorithm identifier used for measurement.
+ * sw_type			Pointer to sw_type buffer.
+ * sw_type_size			Size of the sw_type buffer in bytes.
+ * measurement_value		Pointer to measurement_value buffer.
+ * measurement_value_size	Size of the measurement_value buffer in bytes.
+ * lock_measurement		Boolean flag requesting whether the measurement
+ *				is to be locked.
+ *
+ * PSA_SUCCESS:
+ *	- Success.
+ * PSA_ERROR_INVALID_ARGUMENT:
+ *	- The size of any argument is invalid OR
+ *	- Input Measurement value is NULL OR
+ *	- Input Signer ID is NULL OR
+ *	- Requested slot index is invalid.
+ * PSA_ERROR_BAD_STATE:
+ *	- Request to lock, when slot is already locked.
+ * PSA_ERROR_NOT_PERMITTED:
+ *	- When the requested slot is not accessible to the caller.
+ */
+
+/* Not a standard PSA API, just an extension therefore use the 'rss_' prefix
+ * rather than the usual 'psa_'.
+ */
+psa_status_t
+rss_measured_boot_extend_measurement(uint8_t index,
+				     const uint8_t *signer_id,
+				     size_t signer_id_size,
+				     const uint8_t *version,
+				     size_t version_size,
+				     uint32_t measurement_algo,
+				     const uint8_t *sw_type,
+				     size_t sw_type_size,
+				     const uint8_t *measurement_value,
+				     size_t measurement_value_size,
+				     bool lock_measurement);
+
+#endif /* PSA_MEASURED_BOOT_H */