# Tag Info

4

You are correct. The $Update$ function is called after each invocation of the $Generate$ function, and this does mean that chunking affects the output. Changing both the key and the nonce of an $AES-CTR$ key stream generator to uniformly selected (pseudo) random values will, of course, make the resulting key stream uniformly independent from what it would ...

2

CTR consists of two parts: construction the key stream using a counter, and XOR-ing the output of the key stream with the plaintext/ciphertext. The key stream can be generated using a PRF, in which case it is of course not invertible. The key stream can also be created using a PRP (e.g. a block cipher like AES) in which case it is invertible. As indicated, ...

0

You may want to rethink your whole setup. Like mentioned in the comments, there is a lot more to securely storing files than throwing encryption on them. In particular, you need to be concerned with authentication (CTR without authentication is malleable). I would also look into client side encryption in anything that puts user data in the cloud. Still, ...

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