Using EToken based currency as a payment method

This guide provides a simple way to integrate any EToken cryptocurrency to your website using the Ambisafe Notificator.

Integration steps

Let's say that we want to work with CryptoCarbon currency.

1. Create payment address

First you need to register new cryptocurrency wallet. For this we recommend to go to MyEtherWallet and register new account. Your goal is to finish registration, make a backup of generated keys, and receive a valid address to receive payments. After registration steps you need to find your wallet address - 42 symbols hexadecimal string. It looks like this: 0x38d3d9abbdba8305ebb8b729961xe51bf785aed0

2. Subscribe to notifications

Now you are almost ready to receive payments, but first you need to subscribe to events to know that payment has happened.
Move to your Ambisafe account (sign up here if you don’t have one) and click on "Notificator Service" in account menu and then "Add Filter". There are several templates and by default "EToken" is active, that is what we need.

First field is a Name of filter. You can create many filters, so adequate name can help you to distinguish one filter from another.

Currency symbol. Here we need to choose our desired currency CryptoCarbon (CC) from dropdown menu.

There are prod and stage EToken contracts, so you can create filters for different environments. Currently we want prod.

Event name. EToken has many events, we will look at them in the advanced tutorials, but currently we need only one - Transfer event.

Confirmations means how many blocks need to appear in the network before you will receive notification. If you want start receiving notifications immediately, you can leave this field empty - it has 1 block confirmation by default.

Use the Callback URL field to set URL endpoint from your website or other webservice. It will be used to send POST request with notification in JSON format.

Filtered by section holds additional rules for our filter to make it more specific.
Rule is very straightforward. Every event has several fields and we can filter it by some values. Currently we need only one rule to receive all notifications. Transfer event has field to, that is, recipient. This is our wallet address that we have created before. So we just need to click on "+" button and add new rule with the value “to equal [YOUR_ADDRESS]” using dropdown menus.
All rules are combined by AND operator, so be careful (more about rules you can read in the advanced tutorial).

Click "Save" and be ready to receive notifications!

3. Invoices and payments

In order to make a payment, user should know the next information:
- YOUR_ADDRESS is your wallet address;
- AMOUNT is the price in the chosen currency to be paid;
- INVOICE_ID is the unique ID of invoice at your choice, e.g. from database.

Example: User submits the payment request and selects CryptoCarbon as a payment method. The confirmation page says:
"Payment instructions: please send [AMOUNT] CC to address [YOUR_ADDRESS] and specify this invoice: [INVOICE_ID] as a comment to your transaction".

4. Handle notifications

Notification Service will send notifications to your endpoints on each successful user payment according to your filters information. This notifications will be HTTP POST request with json body like this (PHP example here):

{  
  "from":"0x1ff21eca1c3ba96ed53783ab9c92ffbf77862584",
  "eventName":"Transfer",
  "eventData":{  
    "reference":"[USER_INVOICE_ID]",
    "version":1,
    "symbol":"CC",
    "from":"0x1ff21eca1c3ba96ed53783ab9c92ffbf77862584",
    "to":"[YOUR_ADDRESS]",
    "value":3000
  },
  "transactionHash":"0xb8ad15e40cc01695ac996ddbecb3c1f5536dbd2c3d07d140387f71017ff8cb57",
  "timestamp":1465909825,
  "value":0,
  "blockNumber":1702807,
  "to":"[YOUR_ADDRESS]",
  "logIndex":2,
  "transactionIndex":0,
  "confirmations":1
}

NOTE: value are presented in a base currency units, e.g. CryptoCarbon has base unit 6 means that 3000 tokens should be treated as 0.003.

After receiving notification you can verify it by checking signature. Signature is a Base64 encoded SHA256 HMAC of HTTP body by your secret key. It is stored in Signature HTTP Header.

There are many fields, but currently we are interested in eventData section: to, reference and value fields.
In to we can see our wallet address and in reference an invoice id generated for user. You need to check the value and if all the information is correct, mark this invoice as successful.
Ta-da! You've received your first payment to your address and can finally send the desired stuff to user!