diff --git a/.coveragerc b/.coveragerc
index 876cd72..a9e3436 100644
--- a/.coveragerc
+++ b/.coveragerc
@@ -1,6 +1,6 @@
 [run]
-include =
-    ecies/__init__.py
-    ecies/utils.py
 omit =
     ecies/__main__.py
+[report]
+exclude_also =
+    raise NotImplementedError
diff --git a/.cspell.jsonc b/.cspell.jsonc
new file mode 100644
index 0000000..14b4c06
--- /dev/null
+++ b/.cspell.jsonc
@@ -0,0 +1,25 @@
+{
+  "words": [
+    "bitcointalk",
+    "Cipolla",
+    "Codacy",
+    "Codecov",
+    "coincurve",
+    "dataclass",
+    "ecdh",
+    "ecies",
+    "eciespy",
+    "fromhex",
+    "hashlib",
+    "helloworld",
+    "hexdigest",
+    "hkdf",
+    "pycryptodome",
+    "readablize",
+    "secp",
+    "urandom",
+    "xcfl",
+    "xchacha"
+  ],
+  "ignorePaths": [".cspell.jsonc", "LICENSE"]
+}
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b542294..3146876 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -13,7 +13,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
-        python-version: ["3.7", "3.8", "3.9", "3.10", "3.11"]
+        python-version: ["3.8", "3.9", "3.10", "3.11"] # "3.12-dev"
     steps:
       - uses: actions/checkout@v3
       - uses: actions/setup-python@v4
@@ -31,7 +31,10 @@ jobs:
       - run: brew install automake
         if: matrix.os == 'macos-latest'
 
-      - run: poetry install --only main
+      - run: poetry install
+
+      - name: Run test
+        run: poetry run pytest -s --cov=ecies tests --cov-report xml
 
       - run: ./scripts/ci.sh
 
diff --git a/.gitignore b/.gitignore
index 1285c9c..f061d78 100644
--- a/.gitignore
+++ b/.gitignore
@@ -106,6 +106,6 @@ venv.bak/
 .vscode/
 .DS_Store
 
-prv
-pub
+sk
+pk
 out
diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
index 0000000..5e03499
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,35 @@
+# Release Notes
+
+## 0.4.0
+
+- Drop Python 3.7
+- Revamp documentation
+- Add configuration and XChaCha20 as an optional encryption backend
+
+## 0.3.1 ~ 0.3.13
+
+- Support Python 3.8, 3.9, 3.10, 3.11
+- Drop Python 3.5, 3.6
+- Bump dependencies
+- Update documentation
+
+## 0.3.0
+
+- API change: use `HKDF-sha256` to derive shared keys instead of `sha256`
+
+## 0.2.0
+
+- API change: `ecies.encrypt` and `ecies.decrypt` now can take both hex `str` and raw `bytes`
+- Bump dependencies
+- Update documentation
+
+## 0.1.1 ~ 0.1.9
+
+- Bump dependencies
+- Update documentation
+- Switch to Circle CI
+- Change license to MIT
+
+## 0.1.0
+
+- First beta version release
diff --git a/DETAILS.md b/DETAILS.md
new file mode 100644
index 0000000..94cae07
--- /dev/null
+++ b/DETAILS.md
@@ -0,0 +1,141 @@
+# Mechanism and implementation
+
+This library combines `secp256k1` and `AES-256-GCM` (powered by [`coincurve`](https://github.com/ofek/coincurve) and [`pycryptodome`](https://github.com/Legrandin/pycryptodome)) to provide an API of encrypting with `secp256k1` public key and decrypting with `secp256k1`'s private key. It has two parts generally:
+
+1. Use [ECDH](https://en.wikipedia.org/wiki/Elliptic-curve_Diffie–Hellman) to exchange an AES session key;
+
+   > Notice that the sender public key is generated every time when `ecies.encrypt` is invoked, thus, the AES session key varies.
+   >
+   > We are using HKDF-SHA256 instead of SHA256 to derive the AES keys.
+
+2. Use this AES session key to encrypt/decrypt the data under `AES-256-GCM`.
+
+Basically the encrypted data will be like this:
+
+```plaintext
++-------------------------------+----------+----------+-----------------+
+| 65 Bytes                      | 16 Bytes | 16 Bytes | == data size    |
++-------------------------------+----------+----------+-----------------+
+| Sender Public Key (ephemeral) | Nonce/IV | Tag/MAC  | Encrypted data  |
++-------------------------------+----------+----------+-----------------+
+| sender_pk                     | nonce    | tag      | encrypted_data  |
++-------------------------------+----------+----------+-----------------+
+|           Secp256k1           |              AES-256-GCM              |
++-------------------------------+---------------------------------------+
+```
+
+## Secp256k1
+
+### Glance at ECDH
+
+So, **how** do we calculate the ECDH key under `secp256k1`? If you use a library like [`coincurve`](https://github.com/ofek/coincurve), you might just simply call `k1.ecdh(k2.public_key.format())`, then uh-huh, you got it! Let's see how to do it in simple Python snippets:
+
+```python
+>>> from coincurve import PrivateKey
+>>> k1 = PrivateKey.from_int(3)
+>>> k2 = PrivateKey.from_int(2)
+>>> k1.public_key.format(False).hex() # 65 bytes, False means uncompressed key
+'04f9308a019258c31049344f85f89d5229b531c845836f99b08601f113bce036f9388f7b0f632de8140fe337e62a37f3566500a99934c2231b6cb9fd7584b8e672'
+>>> k2.public_key.format(False).hex() # 65 bytes
+'04c6047f9441ed7d6d3045406e95c07cd85c778e4b8cef3ca7abac09b95c709ee51ae168fea63dc339a3c58419466ceaeef7f632653266d0e1236431a950cfe52a'
+>>> k1.ecdh(k2.public_key.format()).hex()
+'c7d9ba2fa1496c81be20038e5c608f2fd5d0246d8643783730df6c2bbb855cb2'
+>>> k2.ecdh(k1.public_key.format()).hex()
+'c7d9ba2fa1496c81be20038e5c608f2fd5d0246d8643783730df6c2bbb855cb2'
+```
+
+### Calculate your ecdh key manually
+
+However, as a hacker like you with strong desire to learn something, you must be curious about the magic under the ground.
+
+In one sentence, the `secp256k1`'s ECDH key of `k1` and `k2` is nothing but `sha256(k2.public_key.multiply(k1))`.
+
+```python
+>>> k1.to_int()
+3
+>>> shared = k2.public_key.multiply(k1.secret)
+>>> shared.point()
+(115780575977492633039504758427830329241728645270042306223540962614150928364886,
+ 78735063515800386211891312544505775871260717697865196436804966483607426560663)
+>>> import hashlib
+>>> h = hashlib.sha256()
+>>> h.update(shared.format())
+>>> h.hexdigest()  # here you got the ecdh key same as above!
+'c7d9ba2fa1496c81be20038e5c608f2fd5d0246d8643783730df6c2bbb855cb2'
+```
+
+> Warning: **NEVER** use small integers as private keys on any production systems or storing any valuable assets.
+>
+> Warning: **ALWAYS** use safe methods like [`os.urandom`](https://docs.python.org/3/library/os.html#os.urandom) to generate private keys.
+
+### Math on ecdh
+
+Let's discuss in details. The word _multiply_ here means multiplying a **point** of a public key on elliptic curve (like `(x, y)`) with a **scalar** (like `k`). Here `k` is the integer format of a private key, for instance, it can be `3` for `k1` here, and `(x, y)` here is an extremely large number pair like `(115780575977492633039504758427830329241728645270042306223540962614150928364886, 78735063515800386211891312544505775871260717697865196436804966483607426560663)`.
+
+> Warning: 1 \* (x, y) == (x, y) is always true, since 1 is the **identity element** for multiplication. If you take integer 1 as a private key, the public key will be the [base point](https://en.wikipedia.org/wiki/Elliptic_Curve_Digital_Signature_Algorithm#Signature_generation_algorithm).
+
+Mathematically, the elliptic curve cryptography is based on the fact that you can easily multiply point `A` (aka base point, or public key in ECDH) and scalar `k` (aka private key) to get another point `B` (aka public key), but it's almost impossible to calculate `A` from `B` reversely (which means it's a "one-way function").
+
+### Compressed and uncompressed keys
+
+A point multiplying a scalar can be regarded that this point adds itself multiple times, and the point `B` can be converted to a readable public key in a compressed or uncompressed format.
+
+- Compressed format (`x` coordinate only)
+
+```python
+>>> point = (89565891926547004231252920425935692360644145829622209833684329913297188986597, 12158399299693830322967808612713398636155367887041628176798871954788371653930)
+>>> point == k2.public_key.point()
+True
+>>> prefix = '02' if point[1] % 2 == 0 else '03'
+>>> compressed_key_hex = prefix + hex(point[0])[2:]
+>>> compressed_key = bytes.fromhex(compressed_key_hex)
+>>> compressed_key.hex()
+'02c6047f9441ed7d6d3045406e95c07cd85c778e4b8cef3ca7abac09b95c709ee5'
+```
+
+- Uncompressed format (`(x, y)` coordinate)
+
+```python
+>>> uncompressed_key_hex = '04' + hex(point[0])[2:] + hex(point[1])[2:]
+>>> uncompressed_key = bytes.fromhex(uncompressed_key_hex)
+>>> uncompressed_key.hex()
+'04c6047f9441ed7d6d3045406e95c07cd85c778e4b8cef3ca7abac09b95c709ee51ae168fea63dc339a3c58419466ceaeef7f632653266d0e1236431a950cfe52a'
+```
+
+The format is depicted by the image below from the [bitcoin book](https://github.com/bitcoinbook/bitcoinbook).
+
+![EC public key format](https://raw.githubusercontent.com/bitcoinbook/bitcoinbook/develop/images/mbc2_0407.png)
+
+> If you want to convert the compressed format to uncompressed, basically, you need to calculate `y` from `x` by solving the equation using [Cipolla's Algorithm](https://en.wikipedia.org/wiki/Cipolla's_algorithm):
+>
+> ![y^2=(x^3 + 7) mod p, where p=2^{256}-2^{32}-2^{9}-2^{8}-2^{7}-2^{6}-2^{4}-1](<https://tex.s2cms.ru/svg/%20y%5E2%3D(x%5E3%20%2B%207)%20%5Cbmod%20p%2C%5C%20where%5C%20p%3D2%5E%7B256%7D-2%5E%7B32%7D-2%5E%7B9%7D-2%5E%7B8%7D-2%5E%7B7%7D-2%5E%7B6%7D-2%5E%7B4%7D-1%20>)
+>
+> You can check the [bitcoin wiki](https://en.bitcoin.it/wiki/Secp256k1) and this thread on [bitcointalk.org](https://bitcointalk.org/index.php?topic=644919.msg7205689#msg7205689) for more details.
+
+Then, the shared key between `k1` and `k2` is the `sha256` hash of the **compressed** ECDH public key. It's better to use the compressed format, since you can always get `x` from `x` or `(x, y)` without any calculation.
+
+You may want to ask, what if we don't hash it? Briefly, hash can:
+
+1. Make the shared key's length fixed;
+2. Make it safer since hash functions can remove "weak bits" in the original computed key. Check the introduction section of this [paper](http://cacr.uwaterloo.ca/techreports/1998/corr98-05.pdf) for more details.
+
+> Warning: According to some recent research, although widely used, the `sha256` key derivation function is [not secure enough](https://github.com/ecies/py/issues/82).
+
+## AES
+
+Now we have the shared key, and we can use the `nonce` and `tag` to decrypt. This is quite straight, and the example derives from `pycryptodome`'s [documentation](https://pycryptodome.readthedocs.io/en/latest/src/examples.html#encrypt-data-with-aes).
+
+```python
+>>> from Crypto.Cipher import AES
+>>> key = b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
+>>> nonce = b'\xf3\xe1\xba\x81\r,\x89\x00\xb1\x13\x12\xb7\xc7%V_'
+>>> tag = b'\xec;q\xe1|\x11\xdb\xe3\x14\x84\xda\x94P\xed\xcfl'
+>>> data = b'\x02\xd2\xff\xed\x93\xb8V\xf1H\xb9'
+>>> decipher = AES.new(key, AES.MODE_GCM, nonce=nonce)
+>>> decipher.decrypt_and_verify(data, tag)
+b'helloworld'
+```
+
+> Strictly speaking, `nonce` != `iv`, but this is a little bit off topic, if you are curious, you can check [the comment in `utils/symmetric.py`](./ecies/utils/symmetric.py#L79).
+>
+> Warning: it's dangerous to reuse nonce, if you don't know what you are doing, just follow the default setting.
diff --git a/LICENSE b/LICENSE
index d5c0187..437b2f4 100644
--- a/LICENSE
+++ b/LICENSE
@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2018-2021 Weiliang Li
+Copyright (c) 2018-2023 Weiliang Li
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
diff --git a/README.md b/README.md
index 341e18f..bd11551 100644
--- a/README.md
+++ b/README.md
@@ -20,7 +20,7 @@ You can also check a FastAPI web backend demo [here](https://github.com/kigawas/
 
 ## Install
 
-Install with `pip install eciespy` under Python 3.7+.
+`pip install eciespy`
 
 ## Quick Start
 
@@ -98,183 +98,62 @@ Address: 0x47e801184B3a8ea8E6A4A7A4CFEfEcC76809Da72
 ### Encrypt with public key and decrypt with private key
 
 ```console
-$ echo '0x95d3c5e483e9b1d4f5fc8e79b2deaf51362980de62dbb082a9a4257eef653d7d' > prv
-$ echo '0x98afe4f150642cd05cc9d2fa36458ce0a58567daeaf5fde7333ba9b403011140a4e28911fcf83ab1f457a30b4959efc4b9306f514a4c3711a16a80e3b47eb58b' > pub
-$ echo 'helloworld' | eciespy -e -k pub | eciespy -d -k prv
-helloworld
+$ echo '0x95d3c5e483e9b1d4f5fc8e79b2deaf51362980de62dbb082a9a4257eef653d7d' > sk
+$ echo '0x98afe4f150642cd05cc9d2fa36458ce0a58567daeaf5fde7333ba9b403011140a4e28911fcf83ab1f457a30b4959efc4b9306f514a4c3711a16a80e3b47eb58b' > pk
+$ echo 'hello ecies' | eciespy -e -k pk | eciespy -d -k sk
+hello ecies
 $ echo 'data to encrypt' > data
-$ eciespy -e -k pub -D data -O enc_data
-$ eciespy -d -k prv -D enc_data
+$ eciespy -e -k pk -D data -O enc_data
+$ eciespy -d -k sk -D enc_data
 data to encrypt
-$ rm prv pub data enc_data
+$ rm sk pk data enc_data
 ```
 
-## Mechanism and implementation details
+## Configuration
 
-This library combines `secp256k1` and `AES-256-GCM` (powered by [`coincurve`](https://github.com/ofek/coincurve) and [`pycryptodome`](https://github.com/Legrandin/pycryptodome)) to provide an API of encrypting with `secp256k1` public key and decrypting with `secp256k1`'s private key. It has two parts generally:
+Ephemeral key format in the payload and shared key in the key derivation can be configured as compressed or uncompressed format.
 
-1. Use [ECDH](https://en.wikipedia.org/wiki/Elliptic-curve_Diffie–Hellman) to exchange an AES session key;
+```py
+SymmetricAlgorithm = Literal["aes-256-gcm", "xchacha20"]
+NonceLength = Literal[12, 16]  # only for aes-256-gcm, xchacha20 will always be 24
 
-   > Notice that the sender public key is generated every time when `ecies.encrypt` is invoked, thus, the AES session key varies.
-   >
-   > We are using HKDF-SHA256 instead of SHA256 to derive the AES keys.
+COMPRESSED_PUBLIC_KEY_SIZE = 33
+UNCOMPRESSED_PUBLIC_KEY_SIZE = 65
 
-2. Use this AES session key to encrypt/decrypt the data under `AES-256-GCM`.
 
-Basically the encrypted data will be like this:
+@dataclass()
+class Config:
+    is_ephemeral_key_compressed: bool = False
+    is_hkdf_key_compressed: bool = False
+    symmetric_algorithm: SymmetricAlgorithm = "aes-256-gcm"
+    symmetric_nonce_length: NonceLength = 16
 
-```plaintext
-+-------------------------------+----------+----------+-----------------+
-| 65 Bytes                      | 16 Bytes | 16 Bytes | == data size    |
-+-------------------------------+----------+----------+-----------------+
-| Sender Public Key (ephemeral) | Nonce/IV | Tag/MAC  | Encrypted data  |
-+-------------------------------+----------+----------+-----------------+
-| sender_pk                     | nonce    | tag      | encrypted_data  |
-+-------------------------------+----------+----------+-----------------+
-|           Secp256k1           |              AES-256-GCM              |
-+-------------------------------+---------------------------------------+
-```
-
-### Secp256k1
-
-#### Glance at ECDH
-
-So, **how** do we calculate the ECDH key under `secp256k1`? If you use a library like [`coincurve`](https://github.com/ofek/coincurve), you might just simply call `k1.ecdh(k2.public_key.format())`, then uh-huh, you got it! Let's see how to do it in simple Python snippets:
-
-```python
->>> from coincurve import PrivateKey
->>> k1 = PrivateKey.from_int(3)
->>> k2 = PrivateKey.from_int(2)
->>> k1.public_key.format(False).hex() # 65 bytes, False means uncompressed key
-'04f9308a019258c31049344f85f89d5229b531c845836f99b08601f113bce036f9388f7b0f632de8140fe337e62a37f3566500a99934c2231b6cb9fd7584b8e672'
->>> k2.public_key.format(False).hex() # 65 bytes
-'04c6047f9441ed7d6d3045406e95c07cd85c778e4b8cef3ca7abac09b95c709ee51ae168fea63dc339a3c58419466ceaeef7f632653266d0e1236431a950cfe52a'
->>> k1.ecdh(k2.public_key.format()).hex()
-'c7d9ba2fa1496c81be20038e5c608f2fd5d0246d8643783730df6c2bbb855cb2'
->>> k2.ecdh(k1.public_key.format()).hex()
-'c7d9ba2fa1496c81be20038e5c608f2fd5d0246d8643783730df6c2bbb855cb2'
-```
-
-#### Calculate your ecdh key manually
-
-However, as a hacker like you with strong desire to learn something, you must be curious about the magic under the ground.
-
-In one sentence, the `secp256k1`'s ECDH key of `k1` and `k2` is nothing but `sha256(k2.public_key.multiply(k1))`.
-
-```python
->>> k1.to_int()
-3
->>> shared_pub = k2.public_key.multiply(k1.secret)
->>> shared_pub.point()
-(115780575977492633039504758427830329241728645270042306223540962614150928364886,
- 78735063515800386211891312544505775871260717697865196436804966483607426560663)
->>> import hashlib
->>> h = hashlib.sha256()
->>> h.update(shared_pub.format())
->>> h.hexdigest()  # here you got the ecdh key same as above!
-'c7d9ba2fa1496c81be20038e5c608f2fd5d0246d8643783730df6c2bbb855cb2'
-```
-
-> Warning: **NEVER** use small integers as private keys on any production systems or storing any valuable assets.
->
-> Warning: **ALWAYS** use safe methods like [`os.urandom`](https://docs.python.org/3/library/os.html#os.urandom) to generate private keys.
-
-#### Math on ecdh
-
-Let's discuss in details. The word _multiply_ here means multiplying a **point** of a public key on elliptic curve (like `(x, y)`) with a **scalar** (like `k`). Here `k` is the integer format of a private key, for instance, it can be `3` for `k1` here, and `(x, y)` here is an extremely large number pair like `(115780575977492633039504758427830329241728645270042306223540962614150928364886, 78735063515800386211891312544505775871260717697865196436804966483607426560663)`.
-
-> Warning: 1 \* (x, y) == (x, y) is always true, since 1 is the **identity element** for multiplication. If you take integer 1 as a private key, the public key will be the [base point](https://en.wikipedia.org/wiki/Elliptic_Curve_Digital_Signature_Algorithm#Signature_generation_algorithm).
-
-Mathematically, the elliptic curve cryptography is based on the fact that you can easily multiply point `A` (aka base point, or public key in ECDH) and scalar `k` (aka private key) to get another point `B` (aka public key), but it's almost impossible to calculate `A` from `B` reversely (which means it's a "one-way function").
-
-#### Compressed and uncompressed keys
-
-A point multiplying a scalar can be regarded that this point adds itself multiple times, and the point `B` can be converted to a readable public key in a compressed or uncompressed format.
+    @property
+    def ephemeral_key_size(self):
+        return (
+            COMPRESSED_PUBLIC_KEY_SIZE
+            if self.is_ephemeral_key_compressed
+            else UNCOMPRESSED_PUBLIC_KEY_SIZE
+        )
 
-- Compressed format (`x` coordinate only)
 
-```python
->>> point = (89565891926547004231252920425935692360644145829622209833684329913297188986597, 12158399299693830322967808612713398636155367887041628176798871954788371653930)
->>> point == k2.public_key.point()
-True
->>> prefix = '02' if point[1] % 2 == 0 else '03'
->>> compressed_key_hex = prefix + hex(point[0])[2:]
->>> compressed_key = bytes.fromhex(compressed_key_hex)
->>> compressed_key.hex()
-'02c6047f9441ed7d6d3045406e95c07cd85c778e4b8cef3ca7abac09b95c709ee5'
-```
-
-- Uncompressed format (`(x, y)` coordinate)
-
-```python
->>> uncompressed_key_hex = '04' + hex(point[0])[2:] + hex(point[1])[2:]
->>> uncompressed_key = bytes.fromhex(uncompressed_key_hex)
->>> uncompressed_key.hex()
-'04c6047f9441ed7d6d3045406e95c07cd85c778e4b8cef3ca7abac09b95c709ee51ae168fea63dc339a3c58419466ceaeef7f632653266d0e1236431a950cfe52a'
-```
-
-The format is depicted by the image below from the [bitcoin book](https://github.com/bitcoinbook/bitcoinbook).
-
-![EC public key format](https://raw.githubusercontent.com/bitcoinbook/bitcoinbook/develop/images/mbc2_0407.png)
-
-> If you want to convert the compressed format to uncompressed, basically, you need to calculate `y` from `x` by solving the equation using [Cipolla's Algorithm](https://en.wikipedia.org/wiki/Cipolla's_algorithm):
->
-> ![y^2=(x^3 + 7) mod p, where p=2^{256}-2^{32}-2^{9}-2^{8}-2^{7}-2^{6}-2^{4}-1](<https://tex.s2cms.ru/svg/%20y%5E2%3D(x%5E3%20%2B%207)%20%5Cbmod%20p%2C%5C%20where%5C%20p%3D2%5E%7B256%7D-2%5E%7B32%7D-2%5E%7B9%7D-2%5E%7B8%7D-2%5E%7B7%7D-2%5E%7B6%7D-2%5E%7B4%7D-1%20>)
->
-> You can check the [bitcoin wiki](https://en.bitcoin.it/wiki/Secp256k1) and this thread on [bitcointalk.org](https://bitcointalk.org/index.php?topic=644919.msg7205689#msg7205689) for more details.
-
-Then, the shared key between `k1` and `k2` is the `sha256` hash of the **compressed** ECDH public key. It's better to use the compressed format, since you can always get `x` from `x` or `(x, y)` without any calculation.
-
-You may want to ask, what if we don't hash it? Briefly, hash can:
-
-1. Make the shared key's length fixed;
-2. Make it safer since hash functions can remove "weak bits" in the original computed key. Check the introduction section of this [paper](http://cacr.uwaterloo.ca/techreports/1998/corr98-05.pdf) for more details.
-
-> Warning: According to some recent research, although widely used, the `sha256` key derivation function is [not secure enough](https://github.com/ecies/py/issues/82).
-
-### AES
-
-Now we have the shared key, and we can use the `nonce` and `tag` to decrypt. This is quite straight, and the example derives from `pycryptodome`'s [documentation](https://pycryptodome.readthedocs.io/en/latest/src/examples.html#encrypt-data-with-aes).
-
-```python
->>> from Crypto.Cipher import AES
->>> key = b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
->>> iv = b'\xf3\xe1\xba\x81\r,\x89\x00\xb1\x13\x12\xb7\xc7%V_'
->>> tag = b'\xec;q\xe1|\x11\xdb\xe3\x14\x84\xda\x94P\xed\xcfl'
->>> data = b'\x02\xd2\xff\xed\x93\xb8V\xf1H\xb9'
->>> decipher = AES.new(key, AES.MODE_GCM, nonce=iv)
->>> decipher.decrypt_and_verify(data, tag)
-b'helloworld'
+ECIES_CONFIG = Config()
 ```
 
-> Strictly speaking, `nonce` != `iv`, but this is a little bit off topic, if you are curious, you can check [the comment in `utils.py`](https://github.com/ecies/py/blob/master/ecies/utils.py#L213).
-
-## Release Notes
-
-### 0.3.1 ~ 0.3.13
-
-- Support Python 3.8, 3.9, 3.10, 3.11
-- Drop Python 3.5, 3.6
-- Bump dependencies
-- Update documentation
+For example, if you set `is_ephemeral_key_compressed = true`, the payload would be like: `33 Bytes + AES` instead of `65 Bytes + AES`.
 
-### 0.3.0
+If you set `is_hkdf_key_compressed = true`, the hkdf key would be derived from `ephemeral public key (compressed) + shared public key (compressed)` instead of `ephemeral public key (uncompressed) + shared public key (uncompressed)`.
 
-- API change: use `HKDF-sha256` to derive shared keys instead of `sha256`
+If you set `symmetric_algorithm = "xchacha20"`, plaintext data will encrypted with XChaCha20-Poly1305.
 
-### 0.2.0
+If you set `symmetric_nonce_length = 12`, then the nonce of aes-256-gcm would be 12 bytes. XChaCha20-Poly1305's nonce is always 24 bytes.
 
-- API change: `ecies.encrypt` and `ecies.decrypt` now can take both hex `str` and raw `bytes`
-- Bump dependencies
-- Update documentation
+For compatibility, make sure different applications share the same configuration.
 
-### 0.1.1 ~ 0.1.9
+## Technical details
 
-- Bump dependencies
-- Update documentation
-- Switch to Circle CI
-- Change license to MIT
+They are moved to [DETAILS.md](./DETAILS.md).
 
-### 0.1.0
+## Changelog
 
-- First beta version release
+See [CHANGELOG.md](./CHANGELOG.md).
diff --git a/ecies/__init__.py b/ecies/__init__.py
index 4f50bca..2a41ebf 100644
--- a/ecies/__init__.py
+++ b/ecies/__init__.py
@@ -1,9 +1,19 @@
 from typing import Union
 
 from coincurve import PrivateKey, PublicKey
-from ecies.utils import generate_key, hex2prv, hex2pub, encapsulate, decapsulate, aes_encrypt, aes_decrypt
 
-__all__ = ["encrypt", "decrypt"]
+from .config import ECIES_CONFIG
+from .utils import (
+    decapsulate,
+    encapsulate,
+    generate_key,
+    hex2pk,
+    hex2sk,
+    sym_decrypt,
+    sym_encrypt,
+)
+
+__all__ = ["encrypt", "decrypt", "ECIES_CONFIG"]
 
 
 def encrypt(receiver_pk: Union[str, bytes], msg: bytes) -> bytes:
@@ -22,17 +32,21 @@ def encrypt(receiver_pk: Union[str, bytes], msg: bytes) -> bytes:
     bytes
         Encrypted data
     """
-    ephemeral_key = generate_key()
     if isinstance(receiver_pk, str):
-        receiver_pubkey = hex2pub(receiver_pk)
+        pk = hex2pk(receiver_pk)
     elif isinstance(receiver_pk, bytes):
-        receiver_pubkey = PublicKey(receiver_pk)
+        pk = PublicKey(receiver_pk)
     else:
         raise TypeError("Invalid public key type")
 
-    aes_key = encapsulate(ephemeral_key, receiver_pubkey)
-    cipher_text = aes_encrypt(aes_key, msg)
-    return ephemeral_key.public_key.format(False) + cipher_text
+    ephemeral_sk = generate_key()
+    ephemeral_pk = ephemeral_sk.public_key.format(
+        ECIES_CONFIG.is_ephemeral_key_compressed
+    )
+
+    sym_key = encapsulate(ephemeral_sk, pk)
+    encrypted = sym_encrypt(sym_key, msg)
+    return ephemeral_pk + encrypted
 
 
 def decrypt(receiver_sk: Union[str, bytes], msg: bytes) -> bytes:
@@ -52,15 +66,14 @@ def decrypt(receiver_sk: Union[str, bytes], msg: bytes) -> bytes:
         Plain text
     """
     if isinstance(receiver_sk, str):
-        private_key = hex2prv(receiver_sk)
+        sk = hex2sk(receiver_sk)
     elif isinstance(receiver_sk, bytes):
-        private_key = PrivateKey(receiver_sk)
+        sk = PrivateKey(receiver_sk)
     else:
         raise TypeError("Invalid secret key type")
 
-    pubkey = msg[0:65]  # uncompressed pubkey's length is 65 bytes
-    encrypted = msg[65:]
-    ephemeral_public_key = PublicKey(pubkey)
+    key_size = ECIES_CONFIG.ephemeral_key_size
+    ephemeral_pk, encrypted = PublicKey(msg[0:key_size]), msg[key_size:]
 
-    aes_key = decapsulate(ephemeral_public_key, private_key)
-    return aes_decrypt(aes_key, encrypted)
+    sym_key = decapsulate(ephemeral_pk, sk)
+    return sym_decrypt(sym_key, encrypted)
diff --git a/ecies/__main__.py b/ecies/__main__.py
index 97d2f9a..e58a618 100644
--- a/ecies/__main__.py
+++ b/ecies/__main__.py
@@ -12,7 +12,7 @@
 import argparse
 import sys
 
-from ecies import encrypt, decrypt
+from ecies import decrypt, encrypt
 from ecies.utils import generate_eth_key
 
 __description__ = "Elliptic Curve Integrated Encryption Scheme for secp256k1 in Python"
@@ -68,12 +68,12 @@ def main():
     args = parser.parse_args()
     if args.generate:
         k = generate_eth_key()
-        prv, pub, addr = (
+        sk, pub, addr = (
             k.to_hex(),
             k.public_key.to_hex(),
             k.public_key.to_checksum_address(),
         )
-        print("Private: {}\nPublic: {}\nAddress: {}".format(prv, pub, addr))
+        print("Private: {}\nPublic: {}\nAddress: {}".format(sk, pub, addr))
         return
 
     if args.encrypt == args.decrypt:
@@ -86,18 +86,18 @@ def main():
 
     key = args.key.read().strip()
     if args.encrypt:
-        plaintext = args.data.read()
-        if isinstance(plaintext, str):
-            plaintext = plaintext.encode()
-        data = encrypt(key, plaintext)
+        plain_text = args.data.read()
+        if isinstance(plain_text, str):
+            plain_text = plain_text.encode()
+        data = encrypt(key, plain_text)
         if args.out == sys.stdout:
             data = data.hex()
     else:
-        ciphertext = args.data.read()
-        if isinstance(ciphertext, str):
+        cipher_text = args.data.read()
+        if isinstance(cipher_text, str):
             # if not bytes, suppose hex string
-            ciphertext = bytes.fromhex(ciphertext.strip())
-        data = decrypt(key, ciphertext)
+            cipher_text = bytes.fromhex(cipher_text.strip())
+        data = decrypt(key, cipher_text)
         if args.out == sys.stdout:
             # if binary data, print hex; if not, print utf8
             data = readablize(data)
diff --git a/ecies/config.py b/ecies/config.py
new file mode 100644
index 0000000..9fc47fc
--- /dev/null
+++ b/ecies/config.py
@@ -0,0 +1,27 @@
+from dataclasses import dataclass
+from typing import Literal
+
+SymmetricAlgorithm = Literal["aes-256-gcm", "xchacha20"]
+NonceLength = Literal[12, 16]  # only for aes-256-gcm, xchacha20 will always be 24
+
+COMPRESSED_PUBLIC_KEY_SIZE = 33
+UNCOMPRESSED_PUBLIC_KEY_SIZE = 65
+
+
+@dataclass()
+class Config:
+    is_ephemeral_key_compressed: bool = False
+    is_hkdf_key_compressed: bool = False
+    symmetric_algorithm: SymmetricAlgorithm = "aes-256-gcm"
+    symmetric_nonce_length: NonceLength = 16
+
+    @property
+    def ephemeral_key_size(self):
+        return (
+            COMPRESSED_PUBLIC_KEY_SIZE
+            if self.is_ephemeral_key_compressed
+            else UNCOMPRESSED_PUBLIC_KEY_SIZE
+        )
+
+
+ECIES_CONFIG = Config()
diff --git a/ecies/utils.py b/ecies/utils.py
deleted file mode 100644
index b77a092..0000000
--- a/ecies/utils.py
+++ /dev/null
@@ -1,218 +0,0 @@
-import hashlib
-import codecs
-
-from Crypto.Cipher import AES
-from Crypto.Protocol.KDF import HKDF
-from Crypto.Hash import SHA256
-from coincurve import PrivateKey, PublicKey
-from coincurve.utils import get_valid_secret
-from eth_keys import keys
-
-AES_CIPHER_MODE = AES.MODE_GCM
-AES_KEY_BYTES_LEN = 32
-
-__all__ = [
-    "sha256",
-    "generate_key",
-    "generate_eth_key",
-    "hex2prv",
-    "hex2pub",
-    "aes_encrypt",
-    "aes_decrypt",
-]
-
-
-def remove_0x(s: str) -> str:
-    if s.startswith("0x") or s.startswith("0X"):
-        return s[2:]
-    return s
-
-
-def decode_hex(s: str) -> bytes:
-    return codecs.decode(remove_0x(s), "hex")  # type: ignore
-
-
-def sha256(msg: bytes) -> bytes:
-    """
-    Calculate sha256 hash.
-
-    Parameters
-    ----------
-    msg: bytes
-        message to hash
-
-    Returns
-    -------
-    bytes
-        sha256 hash in bytes
-
-    >>> sha256(b'0'*16).hex()[:8] == 'fcdb4b42'
-    True
-    """
-    return hashlib.sha256(msg).digest()
-
-
-def generate_key() -> PrivateKey:
-    """
-    Generate random (or disposable) EC private key
-
-    Returns
-    -------
-    coincurve.PrivateKey
-        A secp256k1 key
-
-    >>> k = generate_key()
-    """
-    return PrivateKey(get_valid_secret())
-
-
-def generate_eth_key() -> keys.PrivateKey:
-    """
-    Generate random eth private key
-
-    Returns
-    -------
-    eth_keys.keys.PrivateKey
-        An ethereum key
-
-    >>> k = generate_eth_key()
-    """
-    return keys.PrivateKey(get_valid_secret())
-
-
-def hex2pub(pub_hex: str) -> PublicKey:
-    """
-    Convert ethereum hex to EllipticCurvePublicKey
-    The hex should be 65 bytes, but ethereum public key only has 64 bytes
-    So have to add \x04
-
-    Parameters
-    ----------
-    pub_hex: str
-        Public key hex string
-
-    Returns
-    -------
-    coincurve.PublicKey
-        A secp256k1 public key
-
-    >>> data = b'0'*32
-    >>> data_hash = sha256(data)
-    >>> eth_prv = generate_eth_key()
-    >>> cc_prv = hex2prv(eth_prv.to_hex())
-    >>> eth_prv.sign_msg_hash(data_hash).to_bytes() == cc_prv.sign_recoverable(data)
-    True
-    >>> pk_hex = eth_prv.public_key.to_hex()
-    >>> computed_pub = hex2pub(pk_hex)
-    >>> computed_pub == cc_prv.public_key
-    True
-    """
-    uncompressed = decode_hex(pub_hex)
-    if len(uncompressed) == 64:  # eth public key format
-        uncompressed = b"\x04" + uncompressed
-
-    return PublicKey(uncompressed)
-
-
-def hex2prv(prv_hex: str) -> PrivateKey:
-    """
-    Convert ethereum hex to EllipticCurvePrivateKey
-
-    Parameters
-    ----------
-    prv_hex: str
-        Private key hex string
-
-    Returns
-    -------
-    coincurve.PrivateKey
-        A secp256k1 private key
-
-    >>> k = generate_eth_key()
-    >>> sk_hex = k.to_hex()
-    >>> pk_hex = k.public_key.to_hex()
-    >>> computed_prv = hex2prv(sk_hex)
-    >>> computed_prv.to_int() == int(k.to_hex(), 16)
-    True
-    """
-    return PrivateKey(decode_hex(prv_hex))
-
-
-def encapsulate(private_key: PrivateKey, peer_public_key: PublicKey) -> bytes:
-    shared_point = peer_public_key.multiply(private_key.secret)
-    master = private_key.public_key.format(compressed=False) + shared_point.format(
-        compressed=False
-    )
-    derived = HKDF(master, AES_KEY_BYTES_LEN, b"", SHA256)
-    return derived  # type: ignore
-
-
-def decapsulate(public_key: PublicKey, peer_private_key: PrivateKey) -> bytes:
-    shared_point = public_key.multiply(peer_private_key.secret)
-    master = public_key.format(compressed=False) + shared_point.format(compressed=False)
-    derived = HKDF(master, AES_KEY_BYTES_LEN, b"", SHA256)
-    return derived  # type: ignore
-
-
-def aes_encrypt(key: bytes, plain_text: bytes) -> bytes:
-    """
-    AES-GCM encryption
-
-    Parameters
-    ----------
-    key: bytes
-        AES session key, which derived from two secp256k1 keys
-    plain_text: bytes
-        Plain text to encrypt
-
-    Returns
-    -------
-    bytes
-        nonce(16 bytes) + tag(16 bytes) + encrypted data
-    """
-    aes_cipher = AES.new(key, AES_CIPHER_MODE)
-
-    encrypted, tag = aes_cipher.encrypt_and_digest(plain_text)  # type: ignore
-    cipher_text = bytearray()
-    cipher_text.extend(aes_cipher.nonce)  # type: ignore
-    cipher_text.extend(tag)
-    cipher_text.extend(encrypted)
-    return bytes(cipher_text)
-
-
-def aes_decrypt(key: bytes, cipher_text: bytes) -> bytes:
-    """
-    AES-GCM decryption
-
-    Parameters
-    ----------
-    key: bytes
-        AES session key, which derived from two secp256k1 keys
-    cipher_text: bytes
-        Encrypted text:
-            iv(16 bytes) + tag(16 bytes) + encrypted data
-
-    Returns
-    -------
-    bytes
-        Plain text
-
-    >>> data = b'this is test data'
-    >>> key = get_valid_secret()
-    >>> aes_decrypt(key, aes_encrypt(key, data)) == data
-    True
-    >>> import os
-    >>> key = os.urandom(32)
-    >>> aes_decrypt(key, aes_encrypt(key, data)) == data
-    True
-    """
-    iv = cipher_text[:16]
-    tag = cipher_text[16:32]
-    ciphered_data = cipher_text[32:]
-
-    # NOTE
-    # pycryptodome's aes gcm takes nonce as iv
-    # but actually nonce (12 bytes) should be used to generate iv (16 bytes) and iv should be sequential
-    # See https://crypto.stackexchange.com/a/71219
-    aes_cipher = AES.new(key, AES_CIPHER_MODE, nonce=iv)
-    return aes_cipher.decrypt_and_verify(ciphered_data, tag)  # type: ignore
diff --git a/ecies/utils/__init__.py b/ecies/utils/__init__.py
new file mode 100644
index 0000000..afec4df
--- /dev/null
+++ b/ecies/utils/__init__.py
@@ -0,0 +1,23 @@
+from .elliptic import (
+    decapsulate,
+    encapsulate,
+    generate_eth_key,
+    generate_key,
+    hex2pk,
+    hex2sk,
+)
+from .hex import decode_hex, sha256
+from .symmetric import sym_decrypt, sym_encrypt
+
+__all__ = [
+    "sha256",
+    "decode_hex",
+    "sym_encrypt",
+    "sym_decrypt",
+    "generate_key",
+    "generate_eth_key",
+    "hex2sk",
+    "hex2pk",
+    "decapsulate",
+    "encapsulate",
+]
diff --git a/ecies/utils/elliptic.py b/ecies/utils/elliptic.py
new file mode 100644
index 0000000..bef9fa7
--- /dev/null
+++ b/ecies/utils/elliptic.py
@@ -0,0 +1,111 @@
+from coincurve import PrivateKey, PublicKey
+from coincurve.utils import get_valid_secret
+from eth_keys import keys
+
+from ..config import ECIES_CONFIG
+from .hex import decode_hex
+from .symmetric import derive_key
+
+
+def generate_key() -> PrivateKey:
+    """
+    Generate a random coincurve.PrivateKey`
+
+    Returns
+    -------
+    coincurve.PrivateKey
+        A secp256k1 key
+
+    >>> k = generate_key()
+    """
+    return PrivateKey(get_valid_secret())
+
+
+def generate_eth_key() -> keys.PrivateKey:
+    """
+    Generate a random `eth_keys.keys.PrivateKey`
+
+    Returns
+    -------
+    eth_keys.keys.PrivateKey
+        An ethereum key
+
+    >>> k = generate_eth_key()
+    """
+    return keys.PrivateKey(get_valid_secret())
+
+
+def hex2pk(pk_hex: str) -> PublicKey:
+    """
+    Convert ethereum hex to `coincurve.PublicKey`
+    The hex should be 65 bytes (uncompressed) or 33 bytes (compressed), but ethereum public key has 64 bytes.
+    `0x04` will be appended if it's an ethereum public key.
+
+    Parameters
+    ----------
+    pk_hex: str
+        Public key hex string
+
+    Returns
+    -------
+    coincurve.PublicKey
+        A secp256k1 public key
+
+    >>> from ecies.utils import sha256
+    >>> data = b'0' * 32
+    >>> data_hash = sha256(data)
+    >>> eth_sk = generate_eth_key()
+    >>> cc_sk = hex2sk(eth_sk.to_hex())
+    >>> eth_sk.sign_msg_hash(data_hash).to_bytes() == cc_sk.sign_recoverable(data)
+    True
+    >>> pk_hex = eth_sk.public_key.to_hex()
+    >>> computed_pk = hex2pk(pk_hex)
+    >>> computed_pk == cc_sk.public_key
+    True
+    """
+    uncompressed = decode_hex(pk_hex)
+    if len(uncompressed) == 64:  # eth public key format
+        uncompressed = b"\x04" + uncompressed
+
+    return PublicKey(uncompressed)
+
+
+def hex2sk(sk_hex: str) -> PrivateKey:
+    """
+    Convert ethereum hex to `coincurve.PrivateKey`
+
+    Parameters
+    ----------
+    sk_hex: str
+        Private key hex string
+
+    Returns
+    -------
+    coincurve.PrivateKey
+        A secp256k1 private key
+
+    >>> k = generate_eth_key()
+    >>> sk_hex = k.to_hex()
+    >>> pk_hex = k.public_key.to_hex()
+    >>> computed_sk = hex2sk(sk_hex)
+    >>> computed_sk.to_int() == int(k.to_hex(), 16)
+    True
+    """
+    return PrivateKey(decode_hex(sk_hex))
+
+
+# private below
+def encapsulate(private_key: PrivateKey, peer_public_key: PublicKey) -> bytes:
+    is_compressed = ECIES_CONFIG.is_hkdf_key_compressed
+    shared_point = peer_public_key.multiply(private_key.secret)
+    master = private_key.public_key.format(is_compressed) + shared_point.format(
+        is_compressed
+    )
+    return derive_key(master)
+
+
+def decapsulate(public_key: PublicKey, peer_private_key: PrivateKey) -> bytes:
+    is_compressed = ECIES_CONFIG.is_hkdf_key_compressed
+    shared_point = public_key.multiply(peer_private_key.secret)
+    master = public_key.format(is_compressed) + shared_point.format(is_compressed)
+    return derive_key(master)
diff --git a/ecies/utils/hex.py b/ecies/utils/hex.py
new file mode 100644
index 0000000..35ca2a3
--- /dev/null
+++ b/ecies/utils/hex.py
@@ -0,0 +1,49 @@
+import codecs
+import hashlib
+
+
+def sha256(msg: bytes) -> bytes:
+    """
+    Calculate sha256 hash.
+
+    Parameters
+    ----------
+    msg: bytes
+        message to hash
+
+    Returns
+    -------
+    bytes
+        sha256 hash in bytes
+
+    >>> sha256(b'0'*16).hex()[:8] == 'fcdb4b42'
+    True
+    """
+    return hashlib.sha256(msg).digest()
+
+
+def decode_hex(s: str) -> bytes:
+    """
+    Decode hex string to bytes. `0x` prefix is optional.
+
+    Parameters
+    ----------
+    s: str
+        hex string
+
+    Returns
+    -------
+    bytes
+        decoded bytes
+
+    >>> decode_hex('0x7468697320697320612074657374') == b'this is a test'
+    True
+    """
+    return codecs.decode(remove_0x(s), "hex")
+
+
+# private below
+def remove_0x(s: str) -> str:
+    if s.startswith("0x") or s.startswith("0X"):
+        return s[2:]
+    return s
diff --git a/ecies/utils/symmetric.py b/ecies/utils/symmetric.py
new file mode 100644
index 0000000..8fe3a23
--- /dev/null
+++ b/ecies/utils/symmetric.py
@@ -0,0 +1,108 @@
+import os
+
+from Crypto.Cipher import AES, ChaCha20_Poly1305
+from Crypto.Hash import SHA256
+from Crypto.Protocol.KDF import HKDF
+
+from ..config import ECIES_CONFIG
+
+AES_CIPHER_MODE = AES.MODE_GCM
+AEAD_TAG_LENGTH = 16
+XCHACHA20_NONCE_LENGTH = 24
+
+
+def sym_encrypt(key: bytes, plain_text: bytes) -> bytes:
+    """
+    Symmetric encryption. AES-256-GCM or XChaCha20-Poly1305.
+
+    Nonce may be 12/16 bytes on AES, 24 bytes on XChaCha. Default is AES-256-GCM with 16 bytes nonce.
+
+    Parameters
+    ----------
+    key: bytes
+        Symmetric encryption session key, which derived from two secp256k1 keys
+    plain_text: bytes
+        Plain text to encrypt
+
+    Returns
+    -------
+    bytes
+        nonce + tag(16 bytes) + encrypted data
+    """
+    algorithm = ECIES_CONFIG.symmetric_algorithm
+    if algorithm == "aes-256-gcm":
+        nonce_length = ECIES_CONFIG.symmetric_nonce_length
+        nonce = os.urandom(nonce_length)
+        cipher = AES.new(key, AES_CIPHER_MODE, nonce)
+    elif algorithm == "xchacha20":
+        nonce = os.urandom(XCHACHA20_NONCE_LENGTH)
+        cipher = ChaCha20_Poly1305.new(key=key, nonce=nonce)  # type:ignore
+    else:
+        raise NotImplementedError
+
+    encrypted, tag = cipher.encrypt_and_digest(plain_text)
+    cipher_text = bytearray()
+    cipher_text.extend(nonce)
+    cipher_text.extend(tag)
+    cipher_text.extend(encrypted)
+    return bytes(cipher_text)
+
+
+def sym_decrypt(key: bytes, cipher_text: bytes) -> bytes:
+    """
+    AES-GCM decryption. AES-256-GCM or XChaCha20-Poly1305.
+
+    Parameters
+    ----------
+    key: bytes
+        Symmetric encryption session key, which derived from two secp256k1 keys
+    cipher_text: bytes
+        Encrypted text:
+            nonce + tag(16 bytes) + encrypted data
+
+    Returns
+    -------
+    bytes
+        Plain text
+
+    >>> from coincurve.utils import get_valid_secret
+    >>> data = b'this is test data'
+    >>> key = get_valid_secret()
+    >>> sym_decrypt(key, sym_encrypt(key, data)) == data
+    True
+    >>> import os
+    >>> key = os.urandom(32)
+    >>> sym_decrypt(key, sym_encrypt(key, data)) == data
+    True
+    """
+
+    # NOTE
+    # pycryptodome's aes gcm takes nonce as iv
+    # but actually nonce (12 bytes) should be used to generate iv (16 bytes) and iv should be sequential
+    # See https://crypto.stackexchange.com/a/71219
+    # You can configure to use 12 bytes nonce by setting `ECIES_CONFIG.symmetric_nonce_length = 12`
+    # If it's 12 bytes, the nonce can be incremented by 1 for each encryption
+    # If it's 16 bytes, the nonce will be used to hash, so it's meaningless to increment
+
+    algorithm = ECIES_CONFIG.symmetric_algorithm
+    if algorithm == "aes-256-gcm":
+        nonce_length = ECIES_CONFIG.symmetric_nonce_length
+        nonce_tag_length = nonce_length + AEAD_TAG_LENGTH
+        nonce = cipher_text[:nonce_length]
+        tag = cipher_text[nonce_length:nonce_tag_length]
+        ciphered_data = cipher_text[nonce_tag_length:]
+        cipher = AES.new(key, AES_CIPHER_MODE, nonce)
+    elif algorithm == "xchacha20":
+        nonce_tag_length = XCHACHA20_NONCE_LENGTH + AEAD_TAG_LENGTH
+        nonce = cipher_text[:XCHACHA20_NONCE_LENGTH]
+        tag = cipher_text[XCHACHA20_NONCE_LENGTH:nonce_tag_length]
+        ciphered_data = cipher_text[nonce_tag_length:]
+        cipher = ChaCha20_Poly1305.new(key=key, nonce=nonce)  # type:ignore
+    else:
+        raise NotImplementedError
+    return cipher.decrypt_and_verify(ciphered_data, tag)
+
+
+def derive_key(master: bytes) -> bytes:
+    derived = HKDF(master, 32, b"", SHA256)
+    return derived  # type: ignore
diff --git a/poetry.lock b/poetry.lock
index 9221c5f..2443607 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -96,17 +96,6 @@ d = ["aiohttp (>=3.7.4)"]
 jupyter = ["ipython (>=7.8.0)", "tokenize-rt (>=3.2.0)"]
 uvloop = ["uvloop (>=0.15.2)"]
 
-[[package]]
-name = "cached-property"
-version = "1.5.2"
-description = "A decorator for caching properties in classes."
-optional = false
-python-versions = "*"
-files = [
-    {file = "cached-property-1.5.2.tar.gz", hash = "sha256:9fa5755838eecbb2d234c3aa390bd80fbd3ac6b6869109bfc1b499f7bd89a130"},
-    {file = "cached_property-1.5.2-py2.py3-none-any.whl", hash = "sha256:df4f613cf7ad9a588cc381aaf4a512d26265ecebd5eb9e1ba12f1319eb85a6a0"},
-]
-
 [[package]]
 name = "cffi"
 version = "1.15.1"
@@ -263,6 +252,81 @@ files = [
     {file = "colorama-0.4.6.tar.gz", hash = "sha256:08695f5cb7ed6e0531a20572697297273c47b8cae5a63ffc6d6ed5c201be6e44"},
 ]
 
+[[package]]
+name = "coverage"
+version = "7.2.7"
+description = "Code coverage measurement for Python"
+optional = false
+python-versions = ">=3.7"
+files = [
+    {file = "coverage-7.2.7-cp310-cp310-macosx_10_9_x86_64.whl", hash = "sha256:d39b5b4f2a66ccae8b7263ac3c8170994b65266797fb96cbbfd3fb5b23921db8"},
+    {file = "coverage-7.2.7-cp310-cp310-macosx_11_0_arm64.whl", hash = "sha256:6d040ef7c9859bb11dfeb056ff5b3872436e3b5e401817d87a31e1750b9ae2fb"},
+    {file = "coverage-7.2.7-cp310-cp310-manylinux_2_17_aarch64.manylinux2014_aarch64.whl", hash = "sha256:ba90a9563ba44a72fda2e85302c3abc71c5589cea608ca16c22b9804262aaeb6"},
+    {file = "coverage-7.2.7-cp310-cp310-manylinux_2_5_i686.manylinux1_i686.manylinux_2_17_i686.manylinux2014_i686.whl", hash = "sha256:e7d9405291c6928619403db1d10bd07888888ec1abcbd9748fdaa971d7d661b2"},
+    {file = "coverage-7.2.7-cp310-cp310-manylinux_2_5_x86_64.manylinux1_x86_64.manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:31563e97dae5598556600466ad9beea39fb04e0229e61c12eaa206e0aa202063"},
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+    {file = "coverage-7.2.7-cp39-cp39-win_amd64.whl", hash = "sha256:eb393e5ebc85245347950143969b241d08b52b88a3dc39479822e073a1a8eb27"},
+    {file = "coverage-7.2.7-pp37.pp38.pp39-none-any.whl", hash = "sha256:b7b4c971f05e6ae490fef852c218b0e79d4e52f79ef0c8475566584a8fb3e01d"},
+    {file = "coverage-7.2.7.tar.gz", hash = "sha256:924d94291ca674905fe9481f12294eb11f2d3d3fd1adb20314ba89e94f44ed59"},
+]
+
+[package.dependencies]
+tomli = {version = "*", optional = true, markers = "python_full_version <= \"3.11.0a6\" and extra == \"toml\""}
+
+[package.extras]
+toml = ["tomli"]
+
 [[package]]
 name = "cytoolz"
 version = "0.12.2"
@@ -452,7 +516,6 @@ files = [
 ]
 
 [package.dependencies]
-cached-property = {version = ">=1.5.2,<2", markers = "python_version < \"3.8\""}
 cytoolz = {version = ">=0.10.1", markers = "implementation_name == \"cpython\""}
 eth-hash = ">=0.3.1"
 eth-typing = ">=3.0.0"
@@ -464,6 +527,20 @@ doc = ["sphinx (>=5.0.0)", "sphinx-rtd-theme (>=1.0.0)", "towncrier (>=21,<22)"]
 lint = ["black (>=23)", "flake8 (==3.8.3)", "isort (>=5.11.0)", "mypy (==0.971)", "pydocstyle (>=5.0.0)", "types-setuptools"]
 test = ["hypothesis (>=4.43.0)", "mypy (==0.971)", "pytest (>=7.0.0)", "pytest-xdist (>=2.4.0)", "types-setuptools"]
 
+[[package]]
+name = "exceptiongroup"
+version = "1.1.2"
+description = "Backport of PEP 654 (exception groups)"
+optional = false
+python-versions = ">=3.7"
+files = [
+    {file = "exceptiongroup-1.1.2-py3-none-any.whl", hash = "sha256:e346e69d186172ca7cf029c8c1d16235aa0e04035e5750b4b95039e65204328f"},
+    {file = "exceptiongroup-1.1.2.tar.gz", hash = "sha256:12c3e887d6485d16943a309616de20ae5582633e0a2eda17f4e10fd61c1e8af5"},
+]
+
+[package.extras]
+test = ["pytest (>=6)"]
+
 [[package]]
 name = "executing"
 version = "1.2.0"
@@ -480,19 +557,30 @@ tests = ["asttokens", "littleutils", "pytest", "rich"]
 
 [[package]]
 name = "flake8"
-version = "6.0.0"
+version = "6.1.0"
 description = "the modular source code checker: pep8 pyflakes and co"
 optional = false
 python-versions = ">=3.8.1"
 files = [
-    {file = "flake8-6.0.0-py2.py3-none-any.whl", hash = "sha256:3833794e27ff64ea4e9cf5d410082a8b97ff1a06c16aa3d2027339cd0f1195c7"},
-    {file = "flake8-6.0.0.tar.gz", hash = "sha256:c61007e76655af75e6785a931f452915b371dc48f56efd765247c8fe68f2b181"},
+    {file = "flake8-6.1.0-py2.py3-none-any.whl", hash = "sha256:ffdfce58ea94c6580c77888a86506937f9a1a227dfcd15f245d694ae20a6b6e5"},
+    {file = "flake8-6.1.0.tar.gz", hash = "sha256:d5b3857f07c030bdb5bf41c7f53799571d75c4491748a3adcd47de929e34cd23"},
 ]
 
 [package.dependencies]
 mccabe = ">=0.7.0,<0.8.0"
-pycodestyle = ">=2.10.0,<2.11.0"
-pyflakes = ">=3.0.0,<3.1.0"
+pycodestyle = ">=2.11.0,<2.12.0"
+pyflakes = ">=3.1.0,<3.2.0"
+
+[[package]]
+name = "iniconfig"
+version = "2.0.0"
+description = "brain-dead simple config-ini parsing"
+optional = false
+python-versions = ">=3.7"
+files = [
+    {file = "iniconfig-2.0.0-py3-none-any.whl", hash = "sha256:b6a85871a79d2e3b22d2d1b94ac2824226a63c6b741c88f7ae975f18b6778374"},
+    {file = "iniconfig-2.0.0.tar.gz", hash = "sha256:2d91e135bf72d31a410b17c16da610a82cb55f6b0477d1a902134b24a455b8b3"},
+]
 
 [[package]]
 name = "ipython"
@@ -535,21 +623,21 @@ test-extra = ["curio", "matplotlib (!=3.2.0)", "nbformat", "numpy (>=1.21)", "pa
 
 [[package]]
 name = "jedi"
-version = "0.18.2"
+version = "0.19.0"
 description = "An autocompletion tool for Python that can be used for text editors."
 optional = false
 python-versions = ">=3.6"
 files = [
-    {file = "jedi-0.18.2-py2.py3-none-any.whl", hash = "sha256:203c1fd9d969ab8f2119ec0a3342e0b49910045abe6af0a3ae83a5764d54639e"},
-    {file = "jedi-0.18.2.tar.gz", hash = "sha256:bae794c30d07f6d910d32a7048af09b5a39ed740918da923c6b780790ebac612"},
+    {file = "jedi-0.19.0-py2.py3-none-any.whl", hash = "sha256:cb8ce23fbccff0025e9386b5cf85e892f94c9b822378f8da49970471335ac64e"},
+    {file = "jedi-0.19.0.tar.gz", hash = "sha256:bcf9894f1753969cbac8022a8c2eaee06bfa3724e4192470aaffe7eb6272b0c4"},
 ]
 
 [package.dependencies]
-parso = ">=0.8.0,<0.9.0"
+parso = ">=0.8.3,<0.9.0"
 
 [package.extras]
 docs = ["Jinja2 (==2.11.3)", "MarkupSafe (==1.1.1)", "Pygments (==2.8.1)", "alabaster (==0.7.12)", "babel (==2.9.1)", "chardet (==4.0.0)", "commonmark (==0.8.1)", "docutils (==0.17.1)", "future (==0.18.2)", "idna (==2.10)", "imagesize (==1.2.0)", "mock (==1.0.1)", "packaging (==20.9)", "pyparsing (==2.4.7)", "pytz (==2021.1)", "readthedocs-sphinx-ext (==2.1.4)", "recommonmark (==0.5.0)", "requests (==2.25.1)", "six (==1.15.0)", "snowballstemmer (==2.1.0)", "sphinx (==1.8.5)", "sphinx-rtd-theme (==0.4.3)", "sphinxcontrib-serializinghtml (==1.1.4)", "sphinxcontrib-websupport (==1.2.4)", "urllib3 (==1.26.4)"]
-qa = ["flake8 (==3.8.3)", "mypy (==0.782)"]
+qa = ["flake8 (==5.0.4)", "mypy (==0.971)", "types-setuptools (==67.2.0.1)"]
 testing = ["Django (<3.1)", "attrs", "colorama", "docopt", "pytest (<7.0.0)"]
 
 [[package]]
@@ -615,7 +703,6 @@ files = [
 [package.dependencies]
 mypy-extensions = ">=1.0.0"
 tomli = {version = ">=1.1.0", markers = "python_version < \"3.11\""}
-typed-ast = {version = ">=1.4.0,<2", markers = "python_version < \"3.8\""}
 typing-extensions = ">=4.1.0"
 
 [package.extras]
@@ -663,13 +750,13 @@ testing = ["docopt", "pytest (<6.0.0)"]
 
 [[package]]
 name = "pathspec"
-version = "0.11.1"
+version = "0.11.2"
 description = "Utility library for gitignore style pattern matching of file paths."
 optional = false
 python-versions = ">=3.7"
 files = [
-    {file = "pathspec-0.11.1-py3-none-any.whl", hash = "sha256:d8af70af76652554bd134c22b3e8a1cc46ed7d91edcdd721ef1a0c51a84a5293"},
-    {file = "pathspec-0.11.1.tar.gz", hash = "sha256:2798de800fa92780e33acca925945e9a19a133b715067cf165b8866c15a31687"},
+    {file = "pathspec-0.11.2-py3-none-any.whl", hash = "sha256:1d6ed233af05e679efb96b1851550ea95bbb64b7c490b0f5aa52996c11e92a20"},
+    {file = "pathspec-0.11.2.tar.gz", hash = "sha256:e0d8d0ac2f12da61956eb2306b69f9469b42f4deb0f3cb6ed47b9cce9996ced3"},
 ]
 
 [[package]]
@@ -699,18 +786,33 @@ files = [
 
 [[package]]
 name = "platformdirs"
-version = "3.9.1"
+version = "3.10.0"
 description = "A small Python package for determining appropriate platform-specific dirs, e.g. a \"user data dir\"."
 optional = false
 python-versions = ">=3.7"
 files = [
-    {file = "platformdirs-3.9.1-py3-none-any.whl", hash = "sha256:ad8291ae0ae5072f66c16945166cb11c63394c7a3ad1b1bc9828ca3162da8c2f"},
-    {file = "platformdirs-3.9.1.tar.gz", hash = "sha256:1b42b450ad933e981d56e59f1b97495428c9bd60698baab9f3eb3d00d5822421"},
+    {file = "platformdirs-3.10.0-py3-none-any.whl", hash = "sha256:d7c24979f292f916dc9cbf8648319032f551ea8c49a4c9bf2fb556a02070ec1d"},
+    {file = "platformdirs-3.10.0.tar.gz", hash = "sha256:b45696dab2d7cc691a3226759c0d3b00c47c8b6e293d96f6436f733303f77f6d"},
 ]
 
 [package.extras]
-docs = ["furo (>=2023.5.20)", "proselint (>=0.13)", "sphinx (>=7.0.1)", "sphinx-autodoc-typehints (>=1.23,!=1.23.4)"]
-test = ["appdirs (==1.4.4)", "covdefaults (>=2.3)", "pytest (>=7.3.1)", "pytest-cov (>=4.1)", "pytest-mock (>=3.10)"]
+docs = ["furo (>=2023.7.26)", "proselint (>=0.13)", "sphinx (>=7.1.1)", "sphinx-autodoc-typehints (>=1.24)"]
+test = ["appdirs (==1.4.4)", "covdefaults (>=2.3)", "pytest (>=7.4)", "pytest-cov (>=4.1)", "pytest-mock (>=3.11.1)"]
+
+[[package]]
+name = "pluggy"
+version = "1.2.0"
+description = "plugin and hook calling mechanisms for python"
+optional = false
+python-versions = ">=3.7"
+files = [
+    {file = "pluggy-1.2.0-py3-none-any.whl", hash = "sha256:c2fd55a7d7a3863cba1a013e4e2414658b1d07b6bc57b3919e0c63c9abb99849"},
+    {file = "pluggy-1.2.0.tar.gz", hash = "sha256:d12f0c4b579b15f5e054301bb226ee85eeeba08ffec228092f8defbaa3a4c4b3"},
+]
+
+[package.extras]
+dev = ["pre-commit", "tox"]
+testing = ["pytest", "pytest-benchmark"]
 
 [[package]]
 name = "prompt-toolkit"
@@ -753,13 +855,13 @@ tests = ["pytest"]
 
 [[package]]
 name = "pycodestyle"
-version = "2.10.0"
+version = "2.11.0"
 description = "Python style guide checker"
 optional = false
-python-versions = ">=3.6"
+python-versions = ">=3.8"
 files = [
-    {file = "pycodestyle-2.10.0-py2.py3-none-any.whl", hash = "sha256:8a4eaf0d0495c7395bdab3589ac2db602797d76207242c17d470186815706610"},
-    {file = "pycodestyle-2.10.0.tar.gz", hash = "sha256:347187bdb476329d98f695c213d7295a846d1152ff4fe9bacb8a9590b8ee7053"},
+    {file = "pycodestyle-2.11.0-py2.py3-none-any.whl", hash = "sha256:5d1013ba8dc7895b548be5afb05740ca82454fd899971563d2ef625d090326f8"},
+    {file = "pycodestyle-2.11.0.tar.gz", hash = "sha256:259bcc17857d8a8b3b4a2327324b79e5f020a13c16074670f9c8c8f872ea76d0"},
 ]
 
 [[package]]
@@ -816,13 +918,13 @@ files = [
 
 [[package]]
 name = "pyflakes"
-version = "3.0.1"
+version = "3.1.0"
 description = "passive checker of Python programs"
 optional = false
-python-versions = ">=3.6"
+python-versions = ">=3.8"
 files = [
-    {file = "pyflakes-3.0.1-py2.py3-none-any.whl", hash = "sha256:ec55bf7fe21fff7f1ad2f7da62363d749e2a470500eab1b555334b67aa1ef8cf"},
-    {file = "pyflakes-3.0.1.tar.gz", hash = "sha256:ec8b276a6b60bd80defed25add7e439881c19e64850afd9b346283d4165fd0fd"},
+    {file = "pyflakes-3.1.0-py2.py3-none-any.whl", hash = "sha256:4132f6d49cb4dae6819e5379898f2b8cce3c5f23994194c24b77d5da2e36f774"},
+    {file = "pyflakes-3.1.0.tar.gz", hash = "sha256:a0aae034c444db0071aa077972ba4768d40c830d9539fd45bf4cd3f8f6992efc"},
 ]
 
 [[package]]
@@ -839,6 +941,46 @@ files = [
 [package.extras]
 plugins = ["importlib-metadata"]
 
+[[package]]
+name = "pytest"
+version = "7.4.0"
+description = "pytest: simple powerful testing with Python"
+optional = false
+python-versions = ">=3.7"
+files = [
+    {file = "pytest-7.4.0-py3-none-any.whl", hash = "sha256:78bf16451a2eb8c7a2ea98e32dc119fd2aa758f1d5d66dbf0a59d69a3969df32"},
+    {file = "pytest-7.4.0.tar.gz", hash = "sha256:b4bf8c45bd59934ed84001ad51e11b4ee40d40a1229d2c79f9c592b0a3f6bd8a"},
+]
+
+[package.dependencies]
+colorama = {version = "*", markers = "sys_platform == \"win32\""}
+exceptiongroup = {version = ">=1.0.0rc8", markers = "python_version < \"3.11\""}
+iniconfig = "*"
+packaging = "*"
+pluggy = ">=0.12,<2.0"
+tomli = {version = ">=1.0.0", markers = "python_version < \"3.11\""}
+
+[package.extras]
+testing = ["argcomplete", "attrs (>=19.2.0)", "hypothesis (>=3.56)", "mock", "nose", "pygments (>=2.7.2)", "requests", "setuptools", "xmlschema"]
+
+[[package]]
+name = "pytest-cov"
+version = "4.1.0"
+description = "Pytest plugin for measuring coverage."
+optional = false
+python-versions = ">=3.7"
+files = [
+    {file = "pytest-cov-4.1.0.tar.gz", hash = "sha256:3904b13dfbfec47f003b8e77fd5b589cd11904a21ddf1ab38a64f204d6a10ef6"},
+    {file = "pytest_cov-4.1.0-py3-none-any.whl", hash = "sha256:6ba70b9e97e69fcc3fb45bfeab2d0a138fb65c4d0d6a41ef33983ad114be8c3a"},
+]
+
+[package.dependencies]
+coverage = {version = ">=5.2.1", extras = ["toml"]}
+pytest = ">=4.6"
+
+[package.extras]
+testing = ["fields", "hunter", "process-tests", "pytest-xdist", "six", "virtualenv"]
+
 [[package]]
 name = "six"
 version = "1.16.0"
@@ -906,56 +1048,6 @@ files = [
 docs = ["myst-parser", "pydata-sphinx-theme", "sphinx"]
 test = ["argcomplete (>=2.0)", "pre-commit", "pytest", "pytest-mock"]
 
-[[package]]
-name = "typed-ast"
-version = "1.5.5"
-description = "a fork of Python 2 and 3 ast modules with type comment support"
-optional = false
-python-versions = ">=3.6"
-files = [
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-    {file = "typed_ast-1.5.5-cp310-cp310-macosx_11_0_arm64.whl", hash = "sha256:5f7a8c46a8b333f71abd61d7ab9255440d4a588f34a21f126bbfc95f6049e686"},
-    {file = "typed_ast-1.5.5-cp310-cp310-manylinux_2_17_aarch64.manylinux2014_aarch64.whl", hash = "sha256:597fc66b4162f959ee6a96b978c0435bd63791e31e4f410622d19f1686d5e769"},
-    {file = "typed_ast-1.5.5-cp310-cp310-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:d41b7a686ce653e06c2609075d397ebd5b969d821b9797d029fccd71fdec8e04"},
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-    {file = "typed_ast-1.5.5-cp39-cp39-win_amd64.whl", hash = "sha256:335f22ccb244da2b5c296e6f96b06ee9bed46526db0de38d2f0e5a6597b81155"},
-    {file = "typed_ast-1.5.5.tar.gz", hash = "sha256:94282f7a354f36ef5dbce0ef3467ebf6a258e370ab33d5b40c249fa996e590dd"},
-]
-
 [[package]]
 name = "typing-extensions"
 version = "4.7.1"
@@ -980,5 +1072,5 @@ files = [
 
 [metadata]
 lock-version = "2.0"
-python-versions = "^3.7.2"
-content-hash = "9e792624757bc5f5183b737bf6728308ead482d963081ba04ab8a0daf982e8c6"
+python-versions = "^3.8"
+content-hash = "1cb351cf1dac9317996368eea5ed7fe63556a825732e2811f3c469bce469e83d"
diff --git a/pyproject.toml b/pyproject.toml
index d6b818c..11a9890 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -3,7 +3,7 @@ name = "eciespy"
 packages = [
   {include = "ecies"},
 ]
-version = "0.3.13"
+version = "0.4.0"
 # docs
 authors = ["Weiliang Li <to.be.impressive@gmail.com>"]
 description = "Elliptic Curve Integrated Encryption Scheme for secp256k1 in Python"
@@ -33,18 +33,20 @@ keywords = [
 include = ["ecies/py.typed"]
 
 [tool.poetry.dependencies]
-python = "^3.7.2"
+python = "^3.8"
 
 # 3rd party
 coincurve = ">=13,<19"
 eth-keys = "^0.4.0"
-pycryptodome = "^3.15.0"
+pycryptodome = "^3.18.0"
 
 [tool.poetry.group.dev.dependencies]
 black = {version = "^23.7", python = "^3.9"}
 flake8 = {version = "^6.0.0", python = "^3.9"}
 ipython = {version = "^8.14.0", python = "^3.9"}
 mypy = "^1.4.1"
+pytest = "^7.4.0"
+pytest-cov = "^4.1.0"
 
 [tool.poetry.scripts]
 eciespy = "ecies.__main__:main"
@@ -52,3 +54,10 @@ eciespy = "ecies.__main__:main"
 [build-system]
 build-backend = "poetry.core.masonry.api"
 requires = ["poetry-core>=1.0.0"]
+
+[tool.isort]
+multi_line_output = 3
+profile = "black"
+
+[tool.pytest.ini_options]
+addopts = "--doctest-modules"
diff --git a/scripts/ci.sh b/scripts/ci.sh
index 458be90..20d6c53 100755
--- a/scripts/ci.sh
+++ b/scripts/ci.sh
@@ -1,17 +1,10 @@
 #!/bin/sh
 
-# test
-poetry run pip install coverage
-poetry run python -m doctest -v ecies/utils.py
-poetry run coverage run -m unittest discover .
-poetry run coverage report
-poetry run coverage xml
-
 # test cli
 poetry run eciespy -h
 poetry run eciespy -g
-echo '0x95d3c5e483e9b1d4f5fc8e79b2deaf51362980de62dbb082a9a4257eef653d7d' > prv
-echo '0x98afe4f150642cd05cc9d2fa36458ce0a58567daeaf5fde7333ba9b403011140a4e28911fcf83ab1f457a30b4959efc4b9306f514a4c3711a16a80e3b47eb58b' > pub
-echo 'helloworld' | poetry run eciespy -e -k pub -O out
-poetry run eciespy -d -k prv -D out
-rm prv pub out
+echo '0x95d3c5e483e9b1d4f5fc8e79b2deaf51362980de62dbb082a9a4257eef653d7d' > sk
+echo '0x98afe4f150642cd05cc9d2fa36458ce0a58567daeaf5fde7333ba9b403011140a4e28911fcf83ab1f457a30b4959efc4b9306f514a4c3711a16a80e3b47eb58b' > pk
+echo 'hello ecies' | poetry run eciespy -e -k pk -O out
+poetry run eciespy -d -k sk -D out
+rm sk pk out
diff --git a/setup.cfg b/setup.cfg
index 43927b6..d07b120 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -1,4 +1,5 @@
 [flake8]
-ignore = E501, W605
+ignore = E501, W605, E203, W503
 exclude = .git,__pycache__,docs/source/conf.py,old,build,dist,venv
 max-complexity = 10
+max-line-length = 88
diff --git a/tests/test_crypt.py b/tests/test_crypt.py
index ba468f4..a34d656 100644
--- a/tests/test_crypt.py
+++ b/tests/test_crypt.py
@@ -1,75 +1,64 @@
-import os
-import unittest
-
+import pytest
 from coincurve import PrivateKey
-from Crypto.Protocol.KDF import HKDF
-from Crypto.Hash import SHA256
-
-from ecies import encrypt, decrypt
-from ecies.utils import (
-    sha256,
-    encapsulate,
-    decapsulate,
-    generate_eth_key,
-    generate_key,
-    aes_encrypt,
-    aes_decrypt,
-)
-
-
-class TestCrypt(unittest.TestCase):
-    def setUp(self):
-        self.test_string = b"this is a test"
-        self.big_data = b"0" * 1024 * 1024 * 100  # 100 MB
-
-    def test_hash(self):
-        self.assertEqual(sha256(b"0" * 16).hex()[:8], "fcdb4b42")
-
-    def test_hdkf(self):
-        derived = HKDF(b"secret", 32, b"", SHA256).hex()
-        self.assertEqual(
-            derived, "2f34e5ff91ec85d53ca9b543683174d0cf550b60d5f52b24c97b386cfcf6cbbf"
-        )
-
-        k1 = PrivateKey(secret=bytes([2]))
-        self.assertEqual(k1.to_int(), 2)
-
-        k2 = PrivateKey(secret=bytes([3]))
-        self.assertEqual(k2.to_int(), 3)
-
-        self.assertEqual(encapsulate(k1, k2.public_key), decapsulate(k1.public_key, k2))
-        self.assertEqual(
-            encapsulate(k1, k2.public_key).hex(),
-            "6f982d63e8590c9d9b5b4c1959ff80315d772edd8f60287c9361d548d5200f82",
-        )
-
-    def test_elliptic(self):
-        data = self.test_string
-        k = generate_eth_key()
-        sk_hex = k.to_hex()
+from eth_keys import keys
+
+from ecies import ECIES_CONFIG, decrypt, encrypt
+from ecies.utils import generate_eth_key, generate_key
+from ecies.utils.hex import decode_hex
+
+data = b"this is a test"
+
+
+def __check(k, compressed=False):
+    sk_hex = k.to_hex()
+    if isinstance(k, PrivateKey):
+        pk_hex = k.public_key.format(compressed).hex()
+    elif isinstance(k, keys.PrivateKey):
         pk_hex = k.public_key.to_hex()
-        self.assertEqual(data, decrypt(sk_hex, encrypt(pk_hex, data)))
-
-        k = generate_key()
-        sk_hex = k.to_hex()
-        pk_hex = k.public_key.format(False).hex()
-        self.assertEqual(data, decrypt(sk_hex, encrypt(pk_hex, data)))
-        self.assertEqual(
-            data, decrypt(bytes.fromhex(sk_hex), encrypt(bytes.fromhex(pk_hex), data))
-        )
-
-        k = generate_key()
-        sk_hex = k.to_hex()
-        pk_hex = k.public_key.format(True).hex()
-        self.assertEqual(data, decrypt(sk_hex, encrypt(pk_hex, data)))
-        self.assertEqual(
-            data, decrypt(bytes.fromhex(sk_hex), encrypt(bytes.fromhex(pk_hex), data))
-        )
-
-        self.assertRaises(TypeError, encrypt, 1, data)
-        self.assertRaises(TypeError, decrypt, 1, encrypt(bytes.fromhex(pk_hex), data))
-
-    def test_aes(self):
-        data = self.big_data
-        key = os.urandom(16)
-        self.assertEqual(data, aes_decrypt(key, aes_encrypt(key, data)))
+    else:
+        raise NotImplementedError
+    assert data == decrypt(sk_hex, encrypt(pk_hex, data))
+    sk_bytes = decode_hex(sk_hex)
+    pk_bytes = decode_hex(pk_hex)
+    if len(pk_bytes) == 64:  # eth
+        pk_bytes = b"\x04" + pk_bytes
+    assert data == decrypt(sk_bytes, encrypt(pk_bytes, data))
+
+
+def test_elliptic():
+    __check(generate_eth_key())
+    __check(generate_key())
+    __check(generate_key(), True)
+
+    with pytest.raises(TypeError):
+        encrypt(1, data)
+
+    k = generate_key()
+    pk_hex = k.public_key.format(True).hex()
+
+    with pytest.raises(TypeError):
+        decrypt(1, encrypt(bytes.fromhex(pk_hex), data))
+
+
+def test_hkdf_config():
+    ECIES_CONFIG.is_hkdf_key_compressed = True
+    __check(generate_key())
+    ECIES_CONFIG.is_hkdf_key_compressed = False
+
+
+def test_ephemeral_key_config():
+    ECIES_CONFIG.is_ephemeral_key_compressed = True
+    __check(generate_key())
+    ECIES_CONFIG.is_ephemeral_key_compressed = False
+
+
+def test_aes_nonce_config():
+    ECIES_CONFIG.symmetric_nonce_length = 12
+    __check(generate_key())
+    ECIES_CONFIG.symmetric_nonce_length = 16
+
+
+def test_sym_config():
+    ECIES_CONFIG.symmetric_algorithm = "xchacha20"
+    __check(generate_key())
+    ECIES_CONFIG.symmetric_algorithm = "aes-256-gcm"
diff --git a/tests/test_utils.py b/tests/test_utils.py
new file mode 100644
index 0000000..0907b8c
--- /dev/null
+++ b/tests/test_utils.py
@@ -0,0 +1,80 @@
+import os
+
+from coincurve import PrivateKey
+
+from ecies import ECIES_CONFIG
+from ecies.utils import (
+    decapsulate,
+    decode_hex,
+    encapsulate,
+    sha256,
+    sym_decrypt,
+    sym_encrypt,
+)
+from ecies.utils.symmetric import derive_key
+
+
+def __check_symmetric_random(data: bytes):
+    key = os.urandom(32)
+    sym_decrypt(key, sym_encrypt(key, data)) == data
+
+
+def test_hash():
+    assert sha256(b"0" * 16).hex()[:8] == "fcdb4b42"
+
+
+def test_hkdf():
+    derived = derive_key(b"secret").hex()
+    assert derived == "2f34e5ff91ec85d53ca9b543683174d0cf550b60d5f52b24c97b386cfcf6cbbf"
+
+
+def test_encapsulate():
+    k1 = PrivateKey(secret=bytes([2]))
+    assert k1.to_int() == 2
+
+    k2 = PrivateKey(secret=bytes([3]))
+    assert k2.to_int() == 3
+
+    assert encapsulate(k1, k2.public_key) == decapsulate(k1.public_key, k2)
+    assert (
+        encapsulate(k1, k2.public_key).hex()
+        == "6f982d63e8590c9d9b5b4c1959ff80315d772edd8f60287c9361d548d5200f82"
+    )
+
+
+def test_aes():
+    # test random
+    __check_symmetric_random("helloworld🌍".encode())
+
+    # test big
+    data = b"1" * 1024 * 1024 * 100  # 100 MB
+    __check_symmetric_random(data)
+
+    # test known
+    key = decode_hex("0000000000000000000000000000000000000000000000000000000000000000")
+    nonce = decode_hex("0xf3e1ba810d2c8900b11312b7c725565f")
+    tag = decode_hex("0Xec3b71e17c11dbe31484da9450edcf6c")
+    encrypted = decode_hex("02d2ffed93b856f148b9")
+    data = b"".join([nonce, tag, encrypted])
+    assert b"helloworld" == sym_decrypt(key, data)
+
+
+def test_xchacha20():
+    ECIES_CONFIG.symmetric_algorithm = "xchacha20"
+
+    # test random
+    __check_symmetric_random("helloworld🌍".encode())
+
+    # test big
+    data = b"1" * 1024 * 1024 * 100  # 100 MB
+    __check_symmetric_random(data)
+
+    # test known
+    key = decode_hex("27bd6ec46292a3b421cdaf8a3f0ca759cbc67bcbe7c5855aa0d1e0700fd0e828")
+    nonce = decode_hex("0xfbd5dd10431af533c403d6f4fa629931e5f31872d2f7e7b6")
+    tag = decode_hex("0X5b5ccc27324af03b7ca92dd067ad6eb5")
+    encrypted = decode_hex("aa0664f3c00a09d098bf")
+    data = b"".join([nonce, tag, encrypted])
+    assert b"helloworld" == sym_decrypt(key, data)
+
+    ECIES_CONFIG.symmetric_algorithm = "aes-256-gcm"