Encrypt disk cache when rendering PDF in Swift for iOS

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//
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//  Copyright © 2017-2026 PSPDFKit GmbH. All rights reserved.
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//
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//  The Nutrient sample applications are licensed with a modified BSD license.
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//  Please see License for details. This notice may not be removed from this file.
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//
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import PSPDFKit
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import PSPDFKitUI
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class EncryptedCacheExample: Example {
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    override init() {
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        super.init()
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        title = "Enable PDFCache encryption"
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        contentDescription = "Wrap cache access into an encryption layer."
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        category = .security
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    }
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    override func invoke(with delegate: ExampleRunnerDelegate) -> UIViewController {
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        let cache = SDK.shared.cache
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        // Clear existing cache
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        cache.clear()
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        // Set new cache directory so this example doesn't interfere with the other examples
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        cache.diskCache.cacheDirectory = "PSPDFKit_encrypted"
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        // In a real use case, you want to protect the password better than hard-coding it here.
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        let password: String = "unsafe-testpassword"
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        // Set up cache encryption handlers.
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        // Encrypting the images will be a 5-10% slowdown, nothing substantial.
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        cache.diskCache.encryptionHelper = { (_ renderRequest: RenderRequest, _ data: Data) in
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            return RNCryptor.encrypt(data: data, withPassword: password)
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        }
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        cache.diskCache.decryptionHelper = { (_ renderRequest: RenderRequest, _ encryptedData: Data) in
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            do {
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                return try RNCryptor.decrypt(data: encryptedData, withPassword: password)
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            } catch {
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                print("Failed to decrypt: \(error.localizedDescription)")
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                return nil
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            }
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        }
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        // Open sample document
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        let document = AssetLoader.document(for: .annualReport)
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        return PDFViewController(document: document)
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    }
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}