---
title: aid
framework: cryptotokenkit
role: symbol
role_heading: Instance Property
path: cryptotokenkit/tksmartcardtoken/aid
---

# aid

The ISO 7816-4 application identifiers of the Smart Card.

## Declaration

```swift
var aid: Data? { get }
```

## Discussion

Discussion This value is specified in the Smart Card token extension’s NSExtensionAttributes property list by the com.apple.ctk.aid attribute. If this attribute specifies multiple AIDs, this parameter represents the application identifier found on the card that is already preselected.  If the com.apple.ctk.aid attribute is not present, no application is automatically preselected and the value of this property is nil. For more information, see App Extension Keys in Information Property List Key Reference.