(Excel) Payeezy HMAC Computation

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

Download Excel Class Modules Chilkat Excel Class Modules

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

Dim crypt As Chilkat.Crypt2
Set crypt = Chilkat.NewCrypt2
Dim prng As Chilkat.Prng
Set prng = Chilkat.NewPrng

' An API key such as y6pWAJNyJyjGv66IsVuWnklkKUPFbb0a

apiKey = "my_api_key"
' An API secret such as 86fbae7030253af3cd15faef2a1f4b67353e41fb6799f576b5093ae52901e6f7

apiSecret = "my_api_secret"
' A token such as fdoa-a480ce8951daa73262734cf102641994c1e55e7cdf4c02b6

token = "my_merchant_token"

' The nonce is a random number (bytes), something like "6057786719490086000"

nonce = prng.GenRandom(8,"decimal")
Debug.Print "nonce = "; nonce

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

timestamp = sbTimestamp.GetAsString()
Debug.Print "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 Chilkat.JsonObject
Set json = Chilkat.NewJsonObject
success = json.UpdateString("merchant_ref","Astonishing-Sale")
success = json.UpdateString("transaction_type","authorize")
success = json.UpdateString("method","token")
success = json.UpdateString("amount","200")
success = json.UpdateString("currency_code","USD")
success = json.UpdateString("token.token_type","FDToken")
success = json.UpdateString("token.token_data.type","visa")
success = json.UpdateString("token.token_data.value","2537446225198291")
success = json.UpdateString("token.token_data.cardholder_name","JohnSmith")
success = json.UpdateString("token.token_data.exp_date","1030")
success = json.UpdateString("token.token_data.special_payment","B")

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

' HMAC the data to produce a hex string.
crypt.EncodingMode = "hexlower"
crypt.MacAlgorithm = "hmac"
success = crypt.SetMacKeyString(apiSecret)
crypt.HashAlgorithm = "sha256"
crypt.Charset = "utf-8"

hexHash = crypt.MacStringENC(sbHmacData.GetAsString())

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

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