check.rb

HASH_KEY = YOUR_KEY
HASH_IV  = YOUR_IV
STORE    = YOUR_STORE_ID

# 假定你有 web 傳回的 params
Digest::SHA256.hexdigest("HashIV=#{HASH_IV}&InvoiceTransNo=#{params[:InvoiceTransNo]}&MerchantID=#{params[:MerchantID]}&MerchantOrderNo=#{params[:MerchantOrderNo]}&RandomNum=#{params[:RandomNum]}&TotalAmt=#{params[:TotalAmt]}&HashKey=#{HASH_KEY}").upcase

issue.rb

HASH_KEY = YOUR_KEY
HASH_IV  = YOUR_IV
STORE    = YOUR_STORE_ID

query = {
  "RespondType" => "JSON",
  "Version" => "1.1",
  "TimeStamp" => "1444963784", # 請以 time() 格式 
  "TransNum" => "",
  "MerchantOrderNo" => "201409170000001",
  "BuyerName" => "王大品",
  "BuyerUBN" => "99112233",
  "BuyerAddress" => "台北市南港區南港路一段 99 號", 
  "BuyerEmail" => "[email protected]",
  "BuyerPhone" => "0955221144", 
  "Category" => "B2B", 
  "TaxType" => "1",
  "TaxRate" => "5",
  "Amt" => "490", 
  "TaxAmt" => "10", 
  "TotalAmt" => "500", 
  "CarrierType" => "",
  "CarrierNum" => "", 
  "LoveCode" => "",
  "PrintFlag" => "Y",
  "ItemName" => "商品一|商品二", # 多項商品時，以「|」分開
  "ItemCount" => "1|2", # 多項商品時，以「|」分開 
  "ItemUnit" => "個|個", # 多項商品時，以「|」分開 
  "ItemPrice" => "300|100", # 多項商品時，以「|」分開 
  "ItemAmt" => "300|200", # 多項商品時，以「|」分開 
  "Comment" => "TEST，備註說明",
  "Status" => "1", # 1=立即開立，0=待開立，3=延遲開立 
  "CreateStatusTime" => "",
  "NotifyEmail" => "1", # 1=通知，0=不通知
}.to_query

cipher = OpenSSL::Cipher::AES256.new(:CBC)
cipher.encrypt
cipher.key = HASH_KEY
cipher.iv  = HASH_IV
crypt = cipher.update(query) + cipher.final

encrypt_data = crypt.unpack("H*").first

uri = URI("https://inv.pay2go.com/API/invoice_issue")

req = Net::HTTP::Post.new(uri.path)
req.set_form_data(:MerchantID_ => STORE,
                    :PostData_ => encrypt_data)
sock = Net::HTTP.new(uri.host, uri.port)
sock.use_ssl = true
res = sock.start {|http| http.request(req) }