Add signing example

Author: sandeepmistry

examples/ECCX08Signing/ECCX08Signing.ino

@@ -0,0 +1,93 @@
+/*
+  ECCX08 Signing
+
+  This sketch uses the ECC508 or ECC608 to sign some data
+  using the private key of a key slot, the signature
+  is printed to the Serial monitor. Then the signature is
+  verified using the public key of the slot.
+
+  NOTE: the input data must be 64 bytes in length!
+
+  Circuit:
+   - MKR board with ECC508 or ECC608 on board
+
+  created 5 November 2019
+  by Sandeep Mistry
+*/
+
+#include <ArduinoECCX08.h>
+
+const byte input[64] = {
+  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
+  0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
+  0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f,
+  0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f
+};
+
+const int slot = 0;
+
+void setup() {
+  Serial.begin(9600);
+  while (!Serial);
+
+  Serial.println("ECCX08 Signing");
+  Serial.println();
+
+  if (!ECCX08.begin()) {
+    Serial.println("Failed to communicate with ECC508/ECC608!");
+    while (1);
+  }
+
+  if (!ECCX08.locked()) {
+    Serial.println("The ECC508/ECC608 is not locked!");
+    while (1);
+  }
+
+  // print the input
+  Serial.print("Input is:                  ");
+  printBufferHex(input, sizeof(input));
+
+  // retrieve the public key
+  byte publicKey[64];
+  ECCX08.generatePublicKey(slot, publicKey);
+
+  // print the public key
+  Serial.print("Public key of slot ");
+  Serial.print(slot);
+  Serial.print(" is:   ");
+  printBufferHex(publicKey, sizeof(publicKey));
+
+  // calculate the signature, input MUST be 64-byte array
+  byte signature[64];
+  ECCX08.ecSign(slot, input, signature);
+
+  // print the signature
+  Serial.print("Signature using slot ");
+  Serial.print(slot);
+  Serial.print(" is: ");
+  printBufferHex(signature, sizeof(signature));
+
+  Serial.println();
+
+  // To make the signature verifcation fail, uncomment the next line:
+  //  signature[0] = 0x00;
+
+  // validate the signature
+  if (ECCX08.ecdsaVerify(input, signature, publicKey)) {
+    Serial.println("Verified signature successfully :D");
+  } else {
+    Serial.println("oh no! failed to verify signature :(");
+  }
+}
+
+void loop() {
+  // do nothing
+}
+
+void printBufferHex(const byte input[], int inputLength) {
+  for (int i = 0; i < inputLength; i++) {
+    Serial.print(input[i] >> 4, HEX);
+    Serial.print(input[i] & 0x0f, HEX);
+  }
+  Serial.println();
+}