Update README

README.md

@@ -2,9 +2,9 @@
 
 AEA OTA/IPSW decryption
 
-## `get_key.py`
+## Grabbing keys with `get_key.py`
 
-Gets a key from an AEA (non OTA; for OTAs, use the key that is provided with your response).
+Gets a key from an AEA (non OTA; for OTAs, use the key that is provided with your response, as they generally do not have embedded key acquisition metadata).
 
 ```shell
 pip3 install -r requirements.txt
@@ -20,41 +20,47 @@ pip3 install -r requirements.txt  # only needed once
 python3 get_key.py <path to AEA>
 ```
 
-## Decrypting/extracting an AEA
-
-### Non-OTAs (IPSWs)
-
-ie. `090-34187-052.dmg.aea`
+## Decrypting an AEA
 
 ```shell
 aea decrypt -i <path to AEA> -o <decrypted output file> -key-value 'base64:<key in base64>'
 ```
 
-### OTAs
+For IPSWs, you will get the unwrapped file (ie. `090-34187-052.dmg.aea` will decrypt to `090-34187-052.dmg`).
+
+For assets, you will get specially crafted AppleArchives (see next section).
+
+## Extracting assets
+
+Assets (including OTA updates) are constructed specially and cannot be extracted with standard (`aa`) tooling. They can be decrypted normally, which will result in an AppleArchive that is not extractable with `aa` (we will call these "asset archives"). `aastuff` must be used to extract them.
 
 ```shell
-make
-./aastuff <path to AEA> <output folder> <key in base64>
+# Decrypt if necessary
+aea decrypt -i <path to AEA> -o <decrypted asset archive> -key-value 'base64:<key in base64>'
+./aastuff <decrypted asset archive> <output folder>
 ```
 
-`aastuff` can also handle unencrypted OTAs:
+`aastuff` can also handle asset archives that are not already decrypted:
 
 ```shell
-aea decrypt -i <path to AEA> -o <decrypted AAR>  -key-value 'base64:<key in base64>'
-./aastuff <decrypted AAR> <output folder>
+./aastuff <path to AEA> <output folder> <key in base64>
 ```
 
 ## Notes
 
+`aastuff` uses `AAAssetExtractor`, functions from `libAppleArchive` in order to extract asset archives. However, it is a pretty barren API and does not offer things like selective extraction.
+
+`aastuff_standalone` uses (mostly) standard `libAppleArchive` functions to extract asset archives. In the future (but not currently), it will be able to offer things such as file listings and selective extraction.
 
+For now, both are built and used in the same way. Once `aastuff_standalone` is fully functional and validated, `aastuff` will be deprecated.
 
 ## Related Projects
 
 - [aea1meta - Siguza](https://github.com/Siguza/aea1meta)
 
 ## Credits
 
-- Siguza - auth data parsing strategy
+- Siguza - auth data parsing strategy, AppleArchive extraction sample code
 - Nicolas - original HPKE code
 - Snoolie - auth data parsing strategy
 - Flagers - AppleArchive assistance