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I’m trying to come up with a way to verify the authenticity of a file that I’m downloading from a server to an embedded system. I’m thinking of using a hash (SHA256 preferably). My main concern is that the file size might be too large to l… Continue reading Hashing a large file on an embedded system
From an embedded systems point of view it is inefficient to put the alg ID after TBS data in a certificate since an embedded system may not have a lot of hashing implementation and thus may not be able to verify the signature… Continue reading Why, in a certificate, TBS is before alg id?
My company develops a WiFi-connected IoT product. I want to make sure that the process of getting the user’s WiFi credentials into the device is as safe as possible. At the moment, the product is in a prototype stage, so we can (and will) … Continue reading How can I properly secure the WiFi setup process of an IoT device?
I am curious if Microcontrolers are effected by the vulnerabilities of Meltdown and Spectre. These devices are not specifically CPUs, and do not run Operating Systems per-say. I’m not really sure I understand the whole specul… Continue reading Are MCUs (Like arduinos) effected by Meltdown?
Firmware over the air (FOTA) is a generic name for performing firmware updates remotely.
Assuming that I have a microcontroller with RW memory and a bootloader, what is the best paradigm to upgrade firmware securely over Bluetooth or simil… Continue reading What are the best practices to implement secured remote firmware updates over-the-air (OTA)?
Currently I have a native PC application that builds and uploads a configuration to an embedded Linux device (i.e. the client). This device connects to Google Calendar via their OAuth2 API. The configuration requires:
A res… Continue reading Is there a good way to store OAuth2 tokens for a native application?
I am trying to build a light web server on an embedded device, and trying to add HTTPS to it by introducing mbedTLS.
I can use Firefox or IE to make connections without any problem.
However, when using Chrome/Chromium/Op… Continue reading HTTPS connection issue on Chrome/Chromium/Opera
I wish to transfer data securely from an arduino (a microcontroller) to a server.
The obvious solution is probably to use TLS, but arduino does not have the capability to run it.
I did not find any other lightweight imple… Continue reading Sending data securely from a microcontroller to a server
I was looking to find to do a project that mixes two of my interests which are IOT and security, after some thinking I came up with an rpi wap that connects to your existing WIFI connection but routes all data through tor. Af… Continue reading iot privacy hub thoughts on features and additions
I am reviewing the security of an embedded system, specifically how it uses the TLS or DTLS protocol to communicate securely. The system implements as few features of the protocol as it can get away with. It doesn’t deviate from the protocol as such, but it may not always be strictly compliant with all applicable RFC. My objective is to determine whether the choice of security parameters are safe.
I will have to do this again for other similar systems, hence my question is somewhat general rather than being about a specific system.
The security objectives of using (D)TLS are the usual one: an attacker could intercept network traffic (active man-in-the-middle). We want to ensure that the client is talking to the server it thinks it’s talking to and that a third party cannot obtain or modify transmitted data (confidentiality and integrity of traffic on the connection). Client authentication is sometimes desired as well.
These are embedded (IoT) systems with very few resources, and usually interacting in controlled ecosystems. At least, we control the legitimate peers, so compatibility with diverse antique clients and servers is not an issue — the concerns are very different from using TLS on the web. A typical endpoint client only speaks one or two ciphersuites (“classic” signature-based server authentication, pre-shared key, or one of each). Depending on the scenario, the PKI may or may not be a closed system: some devices live in a world where we can trust CAs to only deliver certificates of a certain form, while others may trust a “public web” CA.
These are devices with stringent constraints on available computing power, RAM size and code size. So they’re generally running stripped down TLS libraries with as few features as possible. I’m talking microcontroller with 128–512kB of RAM, not higher-end devices running Linux.
Are there (D)TLS or X.509 extensions that are important? I’m not concerned with the choice of ciphersuites (nobody uses DES, RC4 or MD5 in my world, or ciphersuites without server authentication) or with key sizes. What I’m worried about is, for example, an implementation that skips checks on certificates (e.g. key usage restriction) which would allow a certificate to be misused. Or a missing check during the handshake that allow some kind of downgrade attack (an endpoint device usually only speaks a single protocol version, but the servers it talks to may support multiple versions). Or a missing extension that allows an active MitM to convince the two parties to settle on mismatched security parameters, or to renegotiate insecurely.
What should I be looking for when reviewing the TLS configuration on a small embedded device?
Continue reading Minimum set of TLS features for an embedded device