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# nonce

A universally unique ID (UUID) value that you define.

```
var nonce: UUID { get }
```

## Discussion

Your server generates a unique [`nonce`](/documentation/StoreKit/SKPaymentDiscount/nonce) when it creates the [`signature`](/documentation/StoreKit/SKPaymentDiscount/signature) string for the payment discount. The string representation of the [`nonce`](/documentation/StoreKit/SKPaymentDiscount/nonce) must be lowercase.

You can use a [`nonce`](/documentation/StoreKit/SKPaymentDiscount/nonce) one time; generate a new one for every buy request.

---

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