Encrypt Custom Fields in Installed Managed Packages

If an installed managed package supports Shield Platform Encryption, you can encrypt custom fields in that package. Turn on encryption for custom fields in installed managed packages from the Encryption Settings page, and then apply encryption to custom fields in your installed managed package.
Available in both Salesforce Classic (not available in all orgs) and Lightning Experience.
Available as an add-on subscription in: Enterprise, Performance, and Unlimited Editions. Requires purchasing Salesforce Shield or Shield Platform Encryption. Available in Developer Edition at no charge.

User Permissions Needed
To view setup: View Setup and Configuration
To encrypt files: Customize Application
  1. From Setup, in the Quick Find box, enter Encryption Settings, and then select Encryption Settings.
  2. In the Advanced Encryption Settings section, turn on Encrypt Custom Fields in Managed Packages.
    You can also enable encryption for managed packages programmatically. For more information, see PlatformEncryptionSettings in Metadata API Developer Guide.
    From now on, if an installed managed package supports encryption, you can encrypt custom fields in that package. Don’t know if your application supports encrypted fields? Look for the Designed to Work With Salesforce Shield marker in your application’s AppExchange listing.
    Salesforce Shield compatibility icon in AppExchange
    If you don’t see this marker, talk to your app vendor.