File content as of revision 0:bed9ac8a7beb:

// https://github.com/rjw245/crypto-in-a-box
#include "mbed.h"
#include "tweetnacl.h"

// standalone test
static const uint8_t secretkey[crypto_secretbox_KEYBYTES] = {
  0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
  0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
  0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
  0, 1
};

static const uint8_t nonce[crypto_secretbox_NONCEBYTES] = {
  0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
  0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
  0, 1, 2, 3
};

// Need crypto_secretbox_ZEROBYTES of room at the beginning
// AND crypto_secretbox_BOXZEROBYTES at the end.
// The crypto_secretbox_BOXZEROBYTES allows an encrypted input to fit
// in the buffer when storage STARTS at index [crypto_secretbox_ZEROBYTES]
#define BUFFER_SIZE (256 + \
                     crypto_secretbox_ZEROBYTES + \
                     crypto_secretbox_BOXZEROBYTES)

static unsigned char input_buffer[BUFFER_SIZE], outdata[BUFFER_SIZE];
static uint8_t input_len = 0;

static const uint8_t msg[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12};



Timer tmr;

main() {
  int r;
  uint32_t us;

  tmr.start();
  memset(input_buffer, 0, sizeof(input_buffer));
  input_len = sizeof(msg);
  memcpy(input_buffer + crypto_secretbox_ZEROBYTES, msg, input_len);
  // encrypt
  us = tmr.read_us();
  r = crypto_secretbox(outdata,
                       input_buffer,
                       input_len + crypto_secretbox_ZEROBYTES,
                       nonce,
                       secretkey);
  us = tmr.read_us() - us;
  printf("r= %d  %d us\n",r,us);


  //decrypt
  memset(input_buffer, 0, sizeof(input_buffer));
  us = tmr.read_us();
  r = crypto_secretbox_open(input_buffer,
                            outdata,
                            input_len + crypto_secretbox_ZEROBYTES,
                            nonce,
                            secretkey);
  us = tmr.read_us() - us;
  printf("r= %d  %d us\n",r,us);
  for (int i = 0; i < 4; i++) printf("%d ",input_buffer[crypto_secretbox_ZEROBYTES + i]);
  printf("\n");
  r = memcmp(msg, input_buffer + crypto_secretbox_ZEROBYTES, input_len);
  printf("result %d\n",r);
}