---
title: signature
framework: storekit
role: symbol
role_heading: Instance Property
path: storekit/skpaymentdiscount/signature
---

# signature

A string representing the properties of a specific promotional offer, cryptographically signed.

## Declaration

```swift
var signature: String { get }
```

## Mentioned in

Implementing promotional offers in your app

## Discussion

Discussion The signature is a string signed with your private key that represents the properties of a specific promotional offer. To keep your private key secure, generate the signature on a server. Generate the signature using the Elliptic Curve Digital Signature Algorithm (ECDSA) with SHA 256. For more information, see Generating a signature for promotional offers.

## See Also

### Validating the Discount

- [nonce](storekit/skpaymentdiscount/nonce.md)
- [timestamp](storekit/skpaymentdiscount/timestamp.md)