input_encrypted.md

Example code for posting encrypted data to the input/post and input/bulk API

1. Start with a request string conforming with the API options above e.g: node=emontx&data={power1:100,power2:200,power3:300}
2. Create an initialization vector.
3. Encrypt using AES-128-CBC.
4. Create a single string starting with the initialization vector followed by the cipher-text result of the AES-128-CBC encryption.
5. Convert to a base64 encoded string.
6. Generate a HMAC_HASH of the data string together, using the emoncms apikey for authorization.
7. Send the encrypted string in the POST body of a request to either input/post or input/bulk with headers properties 'Content-type' and 'Authorization' set as below.
8. Verify the result. The result is a base64 encoded sha256 hash of the json data string.

PHP Example source code:

<?php

$userid = USERID;
$apikey = "WRITE APIKEY";

$data = "node=emontx&data=100,200,300";

// Encrypt data
$iv = openssl_random_pseudo_bytes(16);
$encryptedData = $iv.openssl_encrypt($data, 'AES-128-CBC', hex2bin($apikey), OPENSSL_RAW_DATA, $iv);
$base64EncryptedData = rtrim(strtr(base64_encode($encryptedData), '+/', '-_'), '=');

// Generate hmac_hash for user authorization
$hmac = hash_hmac('sha256',$data,hex2bin($apikey));

// Generate request
$ch = curl_init();
curl_setopt($ch,CURLOPT_URL,"http://localhost/emoncms/input/post");
curl_setopt($ch,CURLOPT_POST,1);

// Set request headers Authorization & Content-Type
curl_setopt($ch,CURLOPT_HTTPHEADER, array(
  "Authorization: $userid:$hmac",
  "Content-Type: aes128cbc"
));

curl_setopt($ch,CURLOPT_POSTFIELDS,$base64EncryptedData);
curl_setopt($ch,CURLOPT_RETURNTRANSFER,true);

$result = curl_exec($ch);
curl_close($ch);

// Generate sha256 hash of data string to compare with returned sha256 hash result
$sha1 = str_replace(array('+','/'),array('-','_'), base64_encode(hash("sha256", $data, true)));

if ($sha1==$result) print "ok"; else print $result;