refactor: use task_id to derive key instead of constructing nonce

- Now the pieces of one task use the same key and nonce
- Key is derived from (the primary key, task_id), so every task uses different key
- EncryptReader will seek corresponding offset to encrypt piece plaintext
- When export encrypted files, we can decrypt whole file stream instead of decrypting every single piece

Signed-off-by: chohee <cc5281@126.com>

Author: ChoHee15

Cargo.lock

@@ -34,12 +34,16 @@ bincode = "1.3.3"
 walkdir = "2.5.0"
 
 # encryption
-# chacha20poly1305 = { version = "0.10", features = ["std"] }
 aes = "0.8"
 ctr = "0.9"
-# chacha20 = "0.9.1"
 cipher = "0.4"
 rand = "0.8" 
+hkdf = "0.12.4"
+sha2 = "0.10.9"
+# TODO: version
+generic-array = "0.14.7"
+# [patch.crates-io]
+# generic-array = { version = "0.14.7" }
 
 [dev-dependencies]
 tempfile.workspace = true