This repository contains a fully working Proof of Concept (PoC) that demonstrates how to reconstruct CyberSource Credit/Debit Card encryption as used on websites such as pokemoncenter.com.

📖 Technical write-up

The implementation mirrors CyberSource’s Flex Microform flow and produces a valid payment token (jti) that can be used during checkout automation.

⚠️ Disclaimer
This project is for educational and research purposes only. You are responsible for complying with all applicable laws, merchant terms of service, and PCI requirements.

Below is a basic example showing how to tokenize a card using a valid Capture Context JWT provided by CyberSource.

func TestTokenizeCard(t *testing.T) {
	client := NewFlexClient()

	// You need a valid capture context JWT from CyberSource
	captureContextJWT := "JWT_TOKEN_HERE"

	card := CardDetails{
		Number:          "4111111111111111",
		SecurityCode:    "123",
		Type:            CardTypeVisa,
		ExpirationMonth: "12",
		ExpirationYear:  "2026",
	}

	token, err := client.TokenizeCard(captureContextJWT, card)
	if err != nil {
		fmt.Printf("Error: %v\n", err)
		return
	}

	fmt.Printf("Token: %s\n", token)
}

Important notes

• client.TokenizeCard makes a direct request to the CyberSource API.
• If you plan to integrate this into a bot or automation flow, you should:
  • Add proxy support, or
  • Avoid the network request entirely and use the CreateCardJWE function instead.

Token Format

The returned value is a JWT that contains the encrypted payment information.

After decoding the JWT (for example using jwt.io), you will see a payload similar to the following:

The jti claim is the payment token required for checkout automation.

To automatically extract the payment token (jti) from the returned JWT, use the following helper function:

import "github.com/golang-jwt/jwt/v5"

func parsePaymentToken(encoded string) (string, error) {
	token, _, err := jwt.NewParser().ParseUnverified(encoded, jwt.MapClaims{})
	if err != nil {
		return "", err
	}

	claims := token.Claims.(jwt.MapClaims)
	jti, ok := claims["jti"]
	if !ok {
		return "", fmt.Errorf("payment token not found")
	}

	parsed, ok := jti.(string)
	if !ok {
		return "", fmt.Errorf("failed to parse payment token")
	}

	return parsed, nil
}

The Capture Context JWT is a short-lived token issued by CyberSource. It defines the encryption keys and parameters used to encrypt card data.

Each merchant may expose this token differently.

On pokemoncenter.com, the Capture Context JWT is returned directly from the following endpoint:

GET /tpci-ecommweb-api/get-payment-iframe-key?microform=true&locale=en-GB
Host: www.pokemoncenter.com

Response

{
  "keyId": "eyJ....."
}

The value of keyId is the Capture Context JWT required for card encryption.

High-level Flow

┌──────────────┐
│   Merchant   │
│   Website    │
└──────┬───────┘
       │
       │ 1. GET Capture Context JWT
       ▼
┌──────────────────────────┐
│ Merchant Backend / API   │
│ (e.g. Pokemon Center)    │
└──────┬───────────────────┘
       │
       │  Capture Context JWT
       ▼
┌──────────────────────────┐
│        Client / PoC      │
│ (This repository)        │
└──────┬───────────────────┘
       │
       │ 2. Encrypt card data
       │    using context JWT
       ▼
┌──────────────────────────┐
│     CyberSource Flex     │
│     Tokenization API    │
└──────┬───────────────────┘
       │
       │ 3. payment JWT
       ▼
┌──────────────────────────┐
│        Client / PoC      │
│  Decode JWT, extract jti │
└──────────┬───────────────┘
           │
           │ 4. paymentToken (jti)
           ▼
┌──────────────────────────┐
│   Checkout / Automation  │
└──────────────────────────┘

Step-by-step Breakdown

• Retrieve Capture Context
  • Client requests a Capture Context JWT from the merchant endpoint.
• Encrypt Card Details
  • Card number, CVV, and expiry are encrypted using the public key defined in the Capture Context JWT.
  • A JWE payload is created.
• Tokenize with CyberSource
  • The encrypted payload is sent to the CyberSource Flex API.
  • CyberSource validates and tokenizes the card data.
• Extract Payment Token
  • CyberSource returns a JWT.
  • The jti claim inside this JWT is the payment token required for checkout.