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nvs_flash: Update documentation at different places to indicate NVS encryotion is supported

This commit is contained in:
Sagar Bijwe 2018-10-04 13:06:23 +05:30
parent 594dcd525b
commit 454b69d2ea
2 changed files with 4 additions and 4 deletions
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4
components/nvs_flash/README.rst
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@ -47,9 +47,9 @@ Please note that the namespaces with same name in different NVS partitions are c
Security, tampering, and robustness
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
NVS library doesn't implement tamper prevention measures. It is possible for anyone with physical access to the flash chip to alter, erase, or add key-value pairs.
NVS is not directly compatible with the ESP32 flash encryption system. However, data can still be stored in encrypted form if NVS encryption is used together with ESP32 flash encryption. Please refer to :ref:`nvs_encryption` for more details.
NVS is not currently compatible with the ESP32 flash encryption system.
If NVS encryption is not used, it is possible for anyone with physical access to the flash chip to alter, erase, or add key-value pairs. With NVS encryption enabled, it is not possible to alter or add a key-value pair and get recognized as a valid pair without knowing corresponding NVS encryption keys. However, there is no tamper-resistance against erase operation.
The library does try to recover from conditions when flash memory is in an inconsistent state. In particular, one should be able to power off the device at any point and time and then power it back on. This should not result in loss of data, expect for the new key-value pair if it was being written at the moment of power off. The library should also be able to initialize properly with any random data present in flash memory.

4
docs/en/security/flash-encryption.rst
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@ -25,7 +25,7 @@ Background
- All "app" type partitions
- Any partition marked with the "encrypted" flag in the partition table
It may be desirable for some data partitions to remain unencrypted for ease of access, or to use flash-friendly update algorithms that are ineffective if the data is encrypted. "NVS" partitions for non-volatile storage cannot be encrypted.
It may be desirable for some data partitions to remain unencrypted for ease of access, or to use flash-friendly update algorithms that are ineffective if the data is encrypted. NVS partitions for non-volatile storage cannot be encrypted since NVS library is not directly compatible with flash encryption. Refer to :ref:`NVS Encryption <nvs_encryption>` for more details.
- The flash encryption key is stored in efuse key block 1, internal to the ESP32 chip. By default, this key is read- and write-protected so software cannot access it or change it.
@ -104,7 +104,7 @@ Data which is read via other SPI read APIs are not decrypted:
- Data read via :func:`esp_spi_flash_read` is not decrypted
- Data read via ROM function :func:`SPIRead` is not decrypted (this function is not supported in esp-idf apps).
- Data stored using the Non-Volatile Storage (NVS) API is always stored and read decrypted.
- Data stored using the Non-Volatile Storage (NVS) API is always stored and read decrypted from the perspective of Flash Encryption. It is up to the library to provide encryption feature if required. Refer to :ref:`NVS Encryption <nvs_encryption>` for more details.
Writing Encrypted Flash