diff --git a/plat/arm/board/tc/plat_tc_mbedtls_config.h b/plat/arm/board/tc/plat_tc_mbedtls_config.h
index f0aa60b..773629c 100644
--- a/plat/arm/board/tc/plat_tc_mbedtls_config.h
+++ b/plat/arm/board/tc/plat_tc_mbedtls_config.h
@@ -22,11 +22,7 @@
 #endif
 
 #define MBEDTLS_PSA_CRYPTO_C
-#define MBEDTLS_HMAC_DRBG_C
-#define MBEDTLS_ENTROPY_C
-#define MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES
-#define MBEDTLS_NO_PLATFORM_ENTROPY
-#define MBEDTLS_TEST_NULL_ENTROPY
+#define MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG
 #define MBEDTLS_ECP_C
 #define MBEDTLS_ECP_DP_SECP384R1_ENABLED
 
diff --git a/plat/arm/board/tc/tc_bl31_setup.c b/plat/arm/board/tc/tc_bl31_setup.c
index ff7809d..80e5370 100644
--- a/plat/arm/board/tc/tc_bl31_setup.c
+++ b/plat/arm/board/tc/tc_bl31_setup.c
@@ -9,6 +9,7 @@
 #include <libfdt.h>
 #include <tc_plat.h>
 
+#include <arch_helpers.h>
 #include <common/bl_common.h>
 #include <common/debug.h>
 #include <drivers/arm/css/css_mhu_doorbell.h>
@@ -19,6 +20,34 @@
 #include <plat/arm/common/plat_arm.h>
 #include <plat/common/platform.h>
 
+#include <psa/crypto_platform.h>
+#include <psa/crypto_types.h>
+#include <psa/crypto_values.h>
+
+#ifdef PLATFORM_TEST_TFM_TESTSUITE
+/*
+ * We pretend using an external RNG (through MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG
+ * mbedTLS config option) so we need to provide an implementation of
+ * mbedtls_psa_external_get_random(). Provide a fake one, since we do not
+ * actually use any of external RNG and this function is only needed during
+ * the execution of TF-M testsuite during exporting the public part of the
+ * delegated attestation key.
+ */
+psa_status_t mbedtls_psa_external_get_random(
+			mbedtls_psa_external_random_context_t *context,
+			uint8_t *output, size_t output_size,
+			size_t *output_length)
+{
+	for (size_t i = 0U; i < output_size; i++) {
+		output[i] = (uint8_t)(read_cntpct_el0() & 0xFFU);
+	}
+
+	*output_length = output_size;
+
+	return PSA_SUCCESS;
+}
+#endif /* PLATFORM_TEST_TFM_TESTSUITE */
+
 static scmi_channel_plat_info_t tc_scmi_plat_info[] = {
 	{
 		.scmi_mbx_mem = CSS_SCMI_PAYLOAD_BASE,