Shield Platform Encryption and the Lightning Experience

Shield Platform Encryption works the same way in the Lightning Experience as it does in Salesforce Classic, with a few minor exceptions.
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.

Notes
Note previews in Lightning are not encrypted.
File Encryption Icon
The icon that indicates that a file is encrypted doesn’t appear in Lightning.