DEV-15573 datasheet(22/31 Pages) SPARKFUN

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The Code

The fresh code that you see when you open up Example3_Verify.ino has place holders. Notice how all the bytes

in each array is simply a bunch of 0x00 s.

uint8_t publicKeyExternal[64] = {

0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,

0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00

};

uint8_t message[32] = {

0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,

0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00

};

uint8_t signature[64] = {

0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,

0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00

};

You will need to delete these and paste in your own unique arrays. You could type them in manually, but it will be

much easier to copy and paste them from the terminal output from Example 2.

Also note, when you highlight text within an Arduino serial monitor window, you must use the keyboard to actually

copy them ( Ctrl + C ). It won't let you right-click to copy.

And the actual verification of the signature happens as a single function call. It is located at the bottom of setup().

// Let's verirfy!

if (atecc.verifySignature(message, signature, publicKeyExternal)) Serial.println("Success! Signa

ture Verified.");

else Serial.println("Verification failure.");

atecc.verifySignature(message, signature, publicKeyExternal) is the actual call. This function will return a

boolean true if all three things are good, and a false if something doesn't add up. If you change a single bit in any

three of the arguments, then it won't verify.

Two nice things to thing about:

1. The only place in the world that could create the signature that will verify (using this public key) is inside

your one unique co-processor. No one else in the world would ever be able to impersonate it. Pretty cool

huh!

2. If any of the message was changed (even just a single bit flipped), then this verification would fail. This

means that you can be very confident that the message was transmitted and received properly. In this way it

is acting as a very robust checksum. It also means that if someone actually intercepted this message, they

won't be able to change anything in the message. Sweet!

Example 4: From Alice to Bob

DEV-15573 Datasheet(PDF) 22 Page - SparkFun Electronics