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CC3135MOD: Encrypted SPI/UART communications between CC3135MOD and Host micro

Mueller
Prodigy 120 points

Part Number: CC3135MOD
Other Parts Discussed in Thread: CC3135

Hey ya'll,

I used a logic analyzer to monitor the SPI traffic between my host microcontroller and the CC3135MOD and was able to capture the SSID and password of the Access Point that I am connecting to in plain text.  For example, using the following to connect to an access point named TestAccessPoint:

SlWlanSecParams_t connectionSecurity;
connectionSecurity.Type = SL_WLAN_SEC_TYPE_WPA_WPA2;
connectionSecurity.Key = "TestPW";
connectionSecurity.KeyLen = sizeof("TestPW");
sl_WlanConnect("TestAccessPoint", sizeof("TestAccessPoint"), 0x01234567, &connectionSecurity, NULL)

The SPI traffic plainly displays "TestAccessPoint" followed by "TestPW".

I am guessing that all communications are transmitted across SPI in plain text including back end credentials, etc.

Are there any options for encrypted or obfuscated communications between the CC3135 and the host microcontroller?  Are there options for storing these values (or any secret values) in the CC3135MODs Flash so they do not need to be sent over SPI during run-time?

  • 0
    Guru 80805 points

    Hi,

    There is no way how to encrypt communication between host and CC3135MOD (SPI or UART). You have options:

    • use can save your WLAN credential into the connection profile(s). But you will need to use automatic connection instead manual connection by sl_WlanConnect() API.
    • use some kind of tamper protection of your product (storing keys into SRAM protected by tamper switch of your cover, etc.)
    • you can migrate to CC3235MOD. This module integrates host MCU (Cortex-M4) and network processor at one silicone. From this reason is SPI bus between host MCU and network processor not accessible to end user.

    Jan