---
title: "Biometric Signatures on iOS | Nutrient SDK"
canonical_url: "https://www.nutrient.io/guides/ios/signatures/digital-signatures/biometric/"
md_url: "https://www.nutrient.io/guides/ios/signatures/digital-signatures/biometric.md"
last_updated: "2026-05-15T19:10:05.036Z"
description: "Discover how biometric signatures can improve security and streamline processes. Learn the benefits and applications of this innovative technology."
---

# Biometric Signatures on iOS

A digital signature’s biometric properties are stored via [`PDFSignatureBiometricProperties`](https://www.nutrient.io/api/ios/documentation/pspdfkit/pdfsignaturebiometricproperties). This information includes things like whether or not the signature was created with a stylus, the size of the signee’s finger, and the timing and pressure information that was collected while writing the signature. Ultimately, this data can be used to create solutions that provide a higher grade of security than traditional digital signatures do. A digital signature can only contain biometric data if an ink signature was used to create it.

The following biometric properties and data points can be captured and stored in a digital signature from the signing user interface (UI):

- [`pressureList`](https://www.nutrient.io/api/ios/documentation/pspdfkit/pdfsignaturebiometricproperties/pressurelist):

  Set to the first, the middle, and the last floating-point intensity values of the created ink signature.

  - If [`inputMethod`](https://www.nutrient.io/api/ios/documentation/pspdfkit/pdfsignaturebiometricproperties/inputmethod) is set to [`.finger`](https://www.nutrient.io/api/ios/documentation/pspdfkit/drawinputmethod/finger), it’s calculated based on the velocity of the drawing.
  - If [`inputMethod`](https://www.nutrient.io/api/ios/documentation/pspdfkit/pdfsignaturebiometricproperties/inputmethod) is set to [`.applePencil`](https://www.nutrient.io/api/ios/documentation/pspdfkit/drawinputmethod/applepencil), it’s calculated based on the Apple Pencil’s azimuth and altitude toward the display.
  - If [`inputMethod`](https://www.nutrient.io/api/ios/documentation/pspdfkit/pdfsignaturebiometricproperties/inputmethod) is set to [`.thirdPartyStylus`](https://www.nutrient.io/api/ios/documentation/pspdfkit/drawinputmethod/thirdpartystylus), it’s calculated using the corresponding stylus driver.

- [`timePointsList`](https://www.nutrient.io/api/ios/documentation/pspdfkit/pdfsignaturebiometricproperties/timepointslist):

  Set to an array of the first, the middle, and the last timestamps during the creation of the ink signature. The timestamps correspond to the values in [`pressureList`](https://www.nutrient.io/api/ios/documentation/pspdfkit/pdfsignaturebiometricproperties/pressurelist) and were taken at the same point in time. They are saved as boxed `TimeInterval` values and set to `Date.timeIntervalSince1970` at the time of the drawing.

- [`touchRadius`](https://www.nutrient.io/api/ios/documentation/pspdfkit/pdfsignaturebiometricproperties/touchradius):
  - If [`inputMethod`](https://www.nutrient.io/api/ios/documentation/pspdfkit/pdfsignaturebiometricproperties/inputmethod) is set to [`.finger`](https://www.nutrient.io/api/ios/documentation/pspdfkit/drawinputmethod/finger) or [`.thirdPartyStylus`](https://www.nutrient.io/api/ios/documentation/pspdfkit/drawinputmethod/thirdpartystylus), the touch radius is set to the average radius of all touches of the created ink signature.
  - If [`inputMethod`](https://www.nutrient.io/api/ios/documentation/pspdfkit/pdfsignaturebiometricproperties/inputmethod) is set to [`.applePencil`](https://www.nutrient.io/api/ios/documentation/pspdfkit/drawinputmethod/applepencil), the altitude angle of the Apple Pencil is used instead.

- [`inputMethod`](https://www.nutrient.io/api/ios/documentation/pspdfkit/pdfsignaturebiometricproperties/inputmethod):

  Set to the most recently used input method of the created ink signature.

You can provide biometric data using a custom [`PDFSignatureBiometricProperties`](https://www.nutrient.io/api/ios/documentation/pspdfkit/pdfsignaturebiometricproperties) object in the [`SigningConfiguration`] instance. This biometric data is then saved alongside the digital signature:

```swift

// Generate the biometric data.
let biometricData = PDFSignatureBiometricProperties(pressureList: pressureList, timePointsList: timepoints, touchRadius: radius, inputMethod:.applePencil)

let signingConfiguration = SigningConfiguration(dataSigner: privateKey, certificates: certificates, biometricData: biometricData)

```

## Collecting biometric data

You can access biometric properties from a [`SignatureFormElement`](https://www.nutrient.io/api/ios/documentation/pspdfkit/signatureformelement) object after the signing process is complete by using [`SignatureFormElement.signatureBiometricProperties(_:)`](https://www.nutrient.io/api/ios/documentation/pspdfkit/signatureformelement/signaturebiometricproperties(_:)), like so:

### SWIFT

```swift

let signedSignatureFormElement: SignatureFormElement =...
var privateKey: PrivateKey =...
let pkcs12: PKCS12 =...
let (privateKey, _) = try await pkcs12.unlockCertificateChain(withPassword: password)
let biometricProperties = signedSignatureFormElement.signatureBiometricProperties(privateKey)

```

### OBJECTIVE-C

```objc

PSPDFSignatureFormElement *signedSignatureFormElement =...
PSPDFPrivateKey *privateKey =...
PSPDFPKCS12 *pkcs12 =...
[pkcs12 unlockWithPassword:password done:^(PSPDFX509 *x509, PSPDFPrivateKey *pkey, NSError *err) {
    privateKey = pkey;
}];

PSPDFSignatureBiometricProperties *biometricProperties = [signedSignatureFormElement signatureBiometricProperties:privateKey];

```
---

## Related pages

- [Signatures in iOS Viewer](/guides/ios/signatures/digital-signatures/built-in-ui.md)
- [Adding a Digital Signature to a PDF on iOS](/guides/ios/features/digital-signatures.md)
- [Sign PDFs and Add Custom Encryption on iOS](/guides/ios/signatures/digital-signatures/custom-signers.md)
- [Digital Signature Standards: CAdES and PAdES](/guides/ios/signatures/digital-signatures/standards.md)
- [Contained Digital Signatures on iOS](/guides/ios/signatures/digital-signatures/contained-signatures.md)
- [Customizing Digital Signatures on iOS](/guides/ios/signatures/digital-signatures/customization.md)
- [Secure digital signatures for iOS PDF libraries](/guides/ios/signatures/digital-signatures/supported-methods.md)
- [Validating a Digital Signature on iOS](/guides/ios/signatures/digital-signatures/validation.md)
- [Troubleshooting](/guides/ios/signatures/digital-signatures/troubleshooting.md)
- [Generate a Self-Signed Certificate for Signing on iOS](/guides/ios/signatures/digital-signatures/generate-certificate.md)