iOS: encrypting file transferred by Airdrop and export compliance

I'm using Airdrop to transfer application internal data between two phones. Because Airdrop was intended for file sharing, it could occur that user choose "save the file" to save the data file in Files app by accident. Since my app is a financial planning app, I'm considering to encrypt the file transferred by Airdrop to keep user's data secure. The encryption only applies to the temp file transferred by Airdrop. Once the app on the receiver phone receivers it, it decrypts the file immediately.

I'm referring to this thread to determine how I should answer the export compliance question if I encrypt the temp file. And I noticed these two exemption items:

(iii) your app uses, accesses, implements or incorporates encryption with key lengths not exceeding 56 bits symmetric, 512 bits asymmetric and/or 112 bit elliptic curve

(iv) your app is a mass market product with key lengths not exceeding 64 bits symmetric, or if no symmetric algorithms, not exceeding 768 bits asymmetric and/or 128 bits elliptic curve.

I don't quite understand the difference between the conditions in the two items (what is a mass market product?). But I don't think either helps, because the ciphers provided by iOS Cryptokit contains only AES and ChaChaPoly - the former takes a minimum key size of 128 bits and the latter takes 256 bits key size.

Since there are a lot of apps using Airdrop to transfer application internal data (I can tell that from the discussions on SO), I wonder how other people deal with this? Is this considered an exemption case?

BTW, I considered other options, but none is satisfying:

1. Don't encrypt the data. Obscure it instead (for example, using something like Caesar cipher). But that feels very unprofessional.
2. Don't use Airdrop. Implement my own data transfer mechanism. For example, start a tiny web server on sender side and the receiver side get the data through HTTPS, which from my understanding is an exemption case. I don't choose this approach because a) Airdrop provides a much better user experience than this approach, b) I'll need to use Bonjour to discover service, which requires local network permission. I'd like to avoid that if possible.

The answer depends on what cipher you use to encrypt the data.

Apple summarises your requirements in a couple of documents.

First, in the CryptoKit documentation

Typically, the use of encryption that’s built into the operating system—for example, when your app makes HTTPS connections using URLSession—is exempt from export documentation upload requirements, whereas the use of proprietary encryption is not. To determine whether your use of encryption is considered exempt, see Determine your export compliance requirements.

This leads you to this document which has a table, that I have shown in part:

Assuming that you use AES from Apple's Crypto Kit framework, the second clause would apply. You don't need to provide any documentation to Apple but you should submit a self classification report to the us government.

The exemptions you listed in your question do not apply since you wouldn't use a symmetric cipher with a key length of 64 or 56 bits.