Add config and test for AES SCA countermeasures
- Add configuration for AES_SCA_COUNTERMEASURES to config.h. By
default the feature is disabled.
- Add AES_SCA_COUNTERMEASURES configuration check to check_config.h
- Add AES_SCA_COUNTERMEASURES test to all.sh
diff --git a/include/mbedtls/check_config.h b/include/mbedtls/check_config.h
index fe9c594..40647d5 100644
--- a/include/mbedtls/check_config.h
+++ b/include/mbedtls/check_config.h
@@ -70,6 +70,10 @@
#error "MBEDTLS_AESNI_C defined, but not all prerequisites"
#endif
+#if defined(MBEDTLS_AES_SCA_COUNTERMEASURES) && !defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
+#error "MBEDTLS_AES_SCA_COUNTERMEASURES defined, but not all prerequisites"
+#endif
+
#if defined(MBEDTLS_CTR_DRBG_C) && !defined(MBEDTLS_AES_C)
#error "MBEDTLS_CTR_DRBG_C defined, but not all prerequisites"
#endif
diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index 87012da..1a2de9a 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -635,6 +635,23 @@
//#define MBEDTLS_AES_ONLY_ENCRYPT
/**
+ * \def MBEDTLS_AES_SCA_COUNTERMEASURES
+ *
+ * Add countermeasures against possible side-channel-attack to AES calculation.
+ *
+ * Uncommenting this macro adds three additional calculation rounds to AES
+ * calculation. Additional rounds are using random data and can occur in any
+ * AES calculation round.
+ *
+ * Tradeoff: Uncommenting this increases ROM footprint by ~800 bytes.
+ * The performance loss is 3/11= 27% with 128 bit AES.
+ *
+ * This option is dependent of \c MBEDTLS_ENTROPY_HARDWARE_ALT.
+ *
+ */
+//#define MBEDTLS_AES_SCA_COUNTERMEASURES
+
+/**
* \def MBEDTLS_CAMELLIA_SMALL_MEMORY
*
* Use less ROM for the Camellia implementation (saves about 768 bytes).