(Click to Enlarge)

For any new authentication cycle, Alice will initiate. User must reset Alice and send a "y" over serial at 115200.

"time-to-live token", because it will become invalid after a set amount of time. Bob sends the token to Alice. Alice

will sign the token using her private ECC key, then send the signature to Bob. Bob will use the token, the

signature, and Alice's Public Key to verify everything.

By creating a new random token, Bob now has the ability to control how long he thinks that token should be valid.

This means that if an attacker intercepted the message, and they tried to send it later, it would no longer be valid.

Bob will also invalidate the token after a set amount of time. For our example it will be 150ms. This prevents any

attacker from intercepting the message, and hanging on to it for later use. So if Alice doesn't respond within the set

window of time (150ms), then Bob will clear out the token, and Alice must ask for another.

Because the token is unique every time, that means that Alice's signature will be unique every time. This prevents

an attacker from trying to impersonate Alice by recording communications, and then later sending one.

Troubleshooting

Need help?

If your product is not working as you expected or you need technical assistance or information, head on over

to the SparkFun Technical Assistance page for some initial troubleshooting.

If you don't find what you need there, the SparkFun Forums are a great place to find and ask for help. If this

is your first visit, you'll need to create a Forum Account to search product forums and post questions.

For extra guidance, checkout the product video, which also includes the examples, laid out in this tutorial.

Resources and Going Further

Now that you've sent signed message between two systems, you are ready to integrate some security into your

projects! In these examples we have used hard-wired serial messages between two Arduinos. That

communication channel could be anything: Bluetooth, RFM69s, Wifi and the internet, you name it! Good luck!

Schematic (PDF)

Eagle Files (ZIP)

Github (Hardware)

Github (Arduino Library)

Microchip ATECC508A DataSheet (PDF)

CryptoAuthLib - Microchip CryptoAuthentication Library (includes python support)

Board Dimensions (PDF) or (PNG)

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