Encryption.swift

    func encrypt(_ text: String) -> String? {
        guard
            let bundle = Bundle(identifier: "com.example.bundle.identifier"),
            let url = bundle.url(forResource: "certificate", withExtension: "der"),
            let certData = try? Data(contentsOf: url),
            let cert = SecCertificateCreateWithData(nil, certData as CFData) else {
                print("Couldn't find/create pinned certificate")
                return nil
        }
        var trust: SecTrust?
        guard SecTrustCreateWithCertificates([cert] as CFTypeRef, SecPolicyCreateBasicX509(), &trust) == errSecSuccess, trust != nil else {
            print("Couldn't create trust with pinned certificate")
            return nil
        }
        guard let key = SecTrustCopyPublicKey(trust!) else {
            print("Couldn't extract public key from certificate")
            return nil
        }
        let algorithm = SecKeyAlgorithm.rsaEncryptionOAEPSHA256AESGCM
        guard SecKeyIsAlgorithmSupported(key, .encrypt, algorithm) else {
            print("Algorithm \(algorithm.rawValue) not supported by key")
            return nil
        }
        guard let plainData = text.data(using: .utf8) else {
            print("Cannot convert plain text to UTF8-encoded data")
            return nil
        }
        var error: Unmanaged<CFError>?
        guard let encryptedData = SecKeyCreateEncryptedData(key, algorithm, plainData as CFData, &error) else {
            print("Encryption failed. Error: " + (error?.takeRetainedValue().localizedDescription ?? "unknown"))
            return nil
        }
        return String(data: encryptedData as Data, encoding: .utf8)
    }