(VB.NET UWP/WinRT) Payeezy HMAC Computation

Demonstrates how to calculate the HMAC for a Payeezy REST request.

Chilkat Universal Windows Platform (UWP) / WinRT Downloads Chilkat for the Universal Windows Platform (UWP)

' This example requires the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

Dim crypt As New Chilkat.Crypt2
Dim prng As New Chilkat.Prng
Dim success As Boolean

' An API key such as y6pWAJNyJyjGv66IsVuWnklkKUPFbb0a
Dim apiKey As String = "my_api_key"
' An API secret such as 86fbae7030253af3cd15faef2a1f4b67353e41fb6799f576b5093ae52901e6f7
Dim apiSecret As String = "my_api_secret"
' A token such as fdoa-a480ce8951daa73262734cf102641994c1e55e7cdf4c02b6
Dim token As String = "my_merchant_token"

' The nonce is a random number (bytes), something like "6057786719490086000"
Dim nonce As String = prng.GenRandom(8,"decimal")
Debug.WriteLine("nonce = " & nonce)

Dim dtNow As New Chilkat.CkDateTime
dtNow.SetFromCurrentSystemTime()
Dim sbTimestamp As New Chilkat.StringBuilder
' Get the epoch timestamp in seconds
sbTimestamp.Append(dtNow.GetAsUnixTimeStr(False))
' Change it to milliseconds
sbTimestamp.Append("000")
' The timestamp is a number similar to this: 1546011905000 (which is a timestamp taken on 28-Dec-2018).
Dim timestamp As String = sbTimestamp.GetAsString()
Debug.WriteLine("timestamp = " & timestamp)

' Generate the following JSON request body:
' 	{
' 	  "merchant_ref": "Astonishing-Sale",
' 	  "transaction_type": "authorize",
' 	  "method": "token",
' 	  "amount": "200",
' 	  "currency_code": "USD",
' 	  "token": {
' 	    "token_type": "FDToken",
' 	    "token_data": {
' 	      "type": "visa",
' 	      "value": "2537446225198291",
' 	      "cardholder_name": "JohnSmith",
' 	      "exp_date": "1030",
' 	      "special_payment": "B"
' 	    }
' 	  }
' 	}

Dim json As New Chilkat.JsonObject
json.UpdateString("merchant_ref","Astonishing-Sale")
json.UpdateString("transaction_type","authorize")
json.UpdateString("method","token")
json.UpdateString("amount","200")
json.UpdateString("currency_code","USD")
json.UpdateString("token.token_type","FDToken")
json.UpdateString("token.token_data.type","visa")
json.UpdateString("token.token_data.value","2537446225198291")
json.UpdateString("token.token_data.cardholder_name","JohnSmith")
json.UpdateString("token.token_data.exp_date","1030")
json.UpdateString("token.token_data.special_payment","B")

' string hashData = apiKey + nonce + timestamp + token + jsonString;
Dim sbHmacData As New Chilkat.StringBuilder
sbHmacData.Append(apiKey)
sbHmacData.Append(nonce)
sbHmacData.Append(timestamp)
sbHmacData.Append(token)
sbHmacData.Append(json.Emit())

' HMAC the data to produce a hex string.
crypt.EncodingMode = "hexlower"
crypt.MacAlgorithm = "hmac"
crypt.SetMacKeyString(apiSecret)
crypt.HashAlgorithm = "sha256"
crypt.Charset = "utf-8"
Dim hexHash As String = crypt.MacStringENC(sbHmacData.GetAsString())

' Now base64 encode the hex string:
Dim sbBase64Hash As New Chilkat.StringBuilder
sbBase64Hash.Append(hexHash)
sbBase64Hash.Encode("base64","utf-8")

Debug.WriteLine("This is the Authorization header to be sent with the payeezy request:")
Debug.WriteLine("Authorization: " & sbBase64Hash.GetAsString())