ESP32 Forum

Hello Guys,
Can you tell mi if this setting o efuses is secure for use.
What I do:
1. Generate key on my host
2. Burn key to efuses
3. Flash plain text app image to device(Enable release mode flash encryption)
4. On first boot soft is automatically encrypted and some efuses are burn

And almost everything is ok but i get serial output like that:

E (630) flash_encrypt: Flash encryption settings error: app is configured for RELEASE but efuses are set for DEVELOPMENT
E (641) flash_encrypt: Mismatch found in security options in bootloader menuconfig and efuse settings. Device is not secure.

It's happen because of Write protection not set for FLASH_CRYPT_CNT, but this register is already set to 0x7f so future writings can't change them effectively.

I can handle this error with BURNING Write protection to FLASH_CRYPT_CNT but question is if is that safe if I won’t burn write protection for this bits.

So summarizing is this below efuses configuration is safe for RELEASE??

Thank you in advance for your help

It’s my summary of bits:

EFUSE_NAME Description = [Meaningful Value] [Readable/Writeable] (Hex Value)
----------------------------------------------------------------------------------------
Security fuses:
FLASH_CRYPT_CNT Flash encryption mode counter = 127 R/W (0x7f)
UART_DOWNLOAD_DIS Disable UART download mode (ESP32 rev3 only) = 0 R/W (0x0)
FLASH_CRYPT_CONFIG Flash encryption config (key tweak bits) = 15 R/W (0xf)
CONSOLE_DEBUG_DISABLE Disable ROM BASIC interpreter fallback = 1 R/W (0x1)
ABS_DONE_0 secure boot enabled for bootloader = 0 R/W (0x0)
ABS_DONE_1 secure boot abstract 1 locked = 0 R/W (0x0)
JTAG_DISABLE Disable JTAG = 1 R/W (0x1)
DISABLE_DL_ENCRYPT Disable flash encryption in UART bootloader = 1 R/W (0x1)
DISABLE_DL_DECRYPT Disable flash decryption in UART bootloader = 1 R/W (0x1)
DISABLE_DL_CACHE Disable flash cache in UART bootloader = 1 R/W (0x1)
BLK1 Flash encryption key
= ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? -/-
BLK2 Secure boot key
= 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 R/W
BLK3 Variable Block 3
= 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 R/W

Efuse fuses:
WR_DIS Efuse write disable mask = 128 R/W (0x80)
RD_DIS Efuse read disablemask = 1 R/W (0x1)
CODING_SCHEME Efuse variable block length scheme = 0 R/W (0x0)
KEY_STATUS Usage of efuse block 3 (reserved) = 0 R/W (0x0)

Config fuses:
XPD_SDIO_FORCE Ignore MTDI pin (GPIO12) for VDD_SDIO on reset = 0 R/W (0x0)
XPD_SDIO_REG If XPD_SDIO_FORCE, enable VDD_SDIO reg on reset = 0 R/W (0x0)
XPD_SDIO_TIEH If XPD_SDIO_FORCE & XPD_SDIO_REG, 1=3.3V 0=1.8V = 0 R/W (0x0)
CLK8M_FREQ 8MHz clock freq override = 52 R/W (0x34)
SPI_PAD_CONFIG_CLK Override SD_CLK pad (GPIO6/SPICLK) = 0 R/W (0x0)
SPI_PAD_CONFIG_Q Override SD_DATA_0 pad (GPIO7/SPIQ) = 0 R/W (0x0)
SPI_PAD_CONFIG_D Override SD_DATA_1 pad (GPIO8/SPID) = 0 R/W (0x0)
SPI_PAD_CONFIG_HD Override SD_DATA_2 pad (GPIO9/SPIHD) = 0 R/W (0x0)
SPI_PAD_CONFIG_CS0 Override SD_CMD pad (GPIO11/SPICS0) = 0 R/W (0x0)
DISABLE_SDIO_HOST Disable SDIO host = 0 R/W (0x0)

Identity fuses:
MAC Factory MAC Address
= b8:f0:09:a9:6c:c0 (CRC 0x36 OK) R/W
CHIP_VER_REV1 Silicon Revision 1 = 1 R/W (0x1)
CHIP_VER_REV2 Silicon Revision 2 = 0 R/W (0x0)
CHIP_VERSION Reserved for future chip versions = 2 R/W (0x2)
CHIP_PACKAGE Chip package identifier = 1 R/W (0x1)

Calibration fuses:
BLK3_PART_RESERVE BLOCK3 partially served for ADC calibration data = 0 R/W (0x0)
ADC_VREF Voltage reference calibration = 1107 R/W (0x1)

Flash voltage (VDD_SDIO) determined by GPIO12 on reset (High for 1.8V, Low/NC for 3.3V).

Thank you WiFive, this error was bit confusing.

For sure I’m not an expert, but maybe function which determine if flash encryption is secure should also check if Flash_crypt_cnt is max to avoid displaying this error

It has been fixed in the latest idf https://github.com/espressif/esp-idf/co ... 3fc52c3051