diff --git a/.cargo/config b/.cargo/config.toml
similarity index 100%
rename from .cargo/config
rename to .cargo/config.toml
diff --git a/.cspell.jsonc b/.cspell.jsonc
index 9a6662c..d9a68d2 100644
--- a/.cspell.jsonc
+++ b/.cspell.jsonc
@@ -32,9 +32,7 @@
   // flagWords - list of words to be always considered incorrect
   // This is useful for offensive words and common spelling errors.
   // For example "hte" should be "the"
-  "flagWords": [
-    "hte"
-  ],
+  "flagWords": ["hte"],
   "ignorePaths": [
     ".git",
     ".github",
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 8a64bef..d773885 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -17,7 +17,7 @@ jobs:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
         toolchain: [stable, beta, nightly]
-        feature: [pure, xchacha20, "pure,aes-12bytes-nonce"]
+        feature: [openssl, pure, xchacha20]
     steps:
       - uses: actions/checkout@v3
       - uses: actions/setup-node@v3
@@ -58,18 +58,24 @@ jobs:
       - name: Check and run lint
         run: cargo check && cargo fmt && cargo clippy
 
-      - name: Run openssl tests
-        run: cargo test
-      - name: Run openssl 12 bytes nonce tests
-        run: cargo test --features aes-12bytes-nonce
-
-      - name: Run pure rust tests
+      - name: Run tests
         run: cargo test --no-default-features --features ${{ matrix.feature }}
+      - name: Run tests with std
+        run: cargo test --no-default-features --features ${{ matrix.feature }},std
+
+      - name: Run tests with 12 bytes nonce
+        run: cargo test --no-default-features --features ${{ matrix.feature }},aes-12bytes-nonce
+        if: matrix.feature != 'xchacha20'
+
+      - name: Run tests with std and 12 bytes nonce
+        run: cargo test --no-default-features --features ${{ matrix.feature }},std,aes-12bytes-nonce
+        if: matrix.feature != 'xchacha20'
 
       - name: Install wasm dep
         run: cargo install wasm-bindgen-cli || true
-      - name: Run wasm tests
+      - name: Run tests on wasm target
         run: cargo test --no-default-features --features ${{ matrix.feature }} --target=wasm32-unknown-unknown
+        if: matrix.feature != 'openssl'
 
       - name: Check cargo package
         run: cargo publish --dry-run
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 78234bb..c7c531d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,7 +1,8 @@
 # Changelog
 
-## 0.2.1 ~ 0.2.5
+## 0.2.1 ~ 0.2.6
 
+- Support `no_std`
 - Revamp documentation
 - Revamp configuration and add xchacha20-poly1305 backend
 - Add configuration for more compatibility
diff --git a/Cargo.toml b/Cargo.toml
index 448a79f..15a3755 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "ecies"
-version = "0.2.5"
+version = "0.2.6"
 # docs
 authors = ["Weiliang Li <to.be.impressive@gmail.com>"]
 description = "Elliptic Curve Integrated Encryption Scheme for secp256k1 in Rust"
@@ -20,13 +20,12 @@ homepage = "https://ecies.org/rs/"
 repository = "https://github.com/ecies/rs"
 
 [dependencies]
-hkdf = "0.12.3"
+hkdf = {version = "0.12.3", default-features = false}
 libsecp256k1 = {version = "0.7.1", default-features = false, features = ["static-context"]}
-once_cell = "1.18.0"
-sha2 = "0.10.7"
+sha2 = {version = "0.10.7", default-features = false}
 
 # openssl aes
-openssl = {version = "0.10.55", optional = true}
+openssl = {version = "0.10.55", default-features = false, optional = true}
 
 # pure rust aes
 aes-gcm = {version = "0.10.2", default-features = false, optional = true}
@@ -35,23 +34,35 @@ typenum = {version = "1.16.0", default-features = false, optional = true}
 # chacha20 cipher
 chacha20poly1305 = {version = "0.10.1", default-features = false, optional = true}
 
-[target.'cfg(target_arch = "wasm32")'.dependencies]
-getrandom = {version = "0.2.10", features = ["js"]}
-rand = {version = "0.8.5", features = ["getrandom"]}
+# random number generator
+getrandom = {version = "0.2.10", default-features = false}
+rand_core = {version = "0.6.4", default-features = false, features = ["getrandom"]}
 
-[target.'cfg(not(target_arch = "wasm32"))'.dependencies]
-rand = {version = "0.8.5"}
+# configuration
+once_cell = {version = "1.18.0", default-features = false}
+parking_lot = "0.12.1"
+
+[target.'cfg(all(target_arch = "wasm32", target_os="unknown"))'.dependencies]
+# only for js (browser or node). if it's not js, like substrate, it won't build
+getrandom = {version = "0.2.10", default-features = false, features = ["js"]}
+wasm-bindgen = {version = "0.2.87", default-features = false}
+
+[target.'cfg(all(target_arch = "wasm32", not(target_os="unknown")))'.dependencies]
+# allows wasm32-wasi to build
+once_cell = {version = "1.18.0", default-features = false, features = ["std"]}
 
 [features]
+std = ["hkdf/std", "sha2/std", "once_cell/std"]
+
 default = ["openssl"]
 
 aes-12bytes-nonce = [] # with feature "openssl" or "pure". default: 16 bytes
 pure = ["aes-gcm/aes", "typenum"]
-xchacha20 = ["chacha20poly1305/std"]
+xchacha20 = ["chacha20poly1305"]
 
 [dev-dependencies]
 criterion = {version = "0.5.1", default-features = false}
-hex = "0.4.3"
+hex = {version = "0.4.3", default-features = false, features = ["alloc"]}
 
 [target.'cfg(target_arch = "wasm32")'.dev-dependencies]
 wasm-bindgen-test = "0.3.37"
diff --git a/README.md b/README.md
index f0f5412..f6956d6 100644
--- a/README.md
+++ b/README.md
@@ -16,6 +16,12 @@ This library can be compiled to the WASM target at your option, see [WASM compat
 
 ## Quick Start
 
+`no_std` is enabled by default. You can enable `std` with `std` feature.
+
+```toml
+ecies = {version = "0.2", features = ["std"]}
+```
+
 ```rust
 use ecies::{decrypt, encrypt, utils::generate_keypair};
 
diff --git a/src/compat.rs b/src/compat.rs
new file mode 100644
index 0000000..3f32299
--- /dev/null
+++ b/src/compat.rs
@@ -0,0 +1,5 @@
+#[cfg(feature = "std")]
+pub(crate) use std::vec::Vec;
+
+#[cfg(not(feature = "std"))]
+pub(crate) use alloc::vec::Vec;
diff --git a/src/config.rs b/src/config.rs
index f10f18b..99949bd 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -1,6 +1,5 @@
-use std::sync::Mutex;
-
 use once_cell::sync::Lazy;
+use parking_lot::RwLock;
 
 use crate::consts::{COMPRESSED_PUBLIC_KEY_SIZE, UNCOMPRESSED_PUBLIC_KEY_SIZE};
 
@@ -12,14 +11,14 @@ pub struct Config {
 }
 
 /// Global config variable
-pub static ECIES_CONFIG: Lazy<Mutex<Config>> = Lazy::new(|| {
+pub static ECIES_CONFIG: Lazy<RwLock<Config>> = Lazy::new(|| {
     let config: Config = Config::default();
-    Mutex::new(config)
+    RwLock::new(config)
 });
 
 /// Update global config
 pub fn update_config(config: Config) {
-    *ECIES_CONFIG.lock().unwrap() = config;
+    *ECIES_CONFIG.write() = config;
 }
 
 /// Reset global config to default
@@ -29,7 +28,7 @@ pub fn reset_config() {
 
 /// Get ephemeral key compressed or not
 pub fn is_ephemeral_key_compressed() -> bool {
-    ECIES_CONFIG.lock().unwrap().is_ephemeral_key_compressed
+    ECIES_CONFIG.read().is_ephemeral_key_compressed
 }
 
 /// Get ephemeral key size: compressed(33) or uncompressed(65)
@@ -43,5 +42,5 @@ pub fn get_ephemeral_key_size() -> usize {
 
 /// Get hkdf key derived from compressed shared point or not
 pub fn is_hkdf_key_compressed() -> bool {
-    ECIES_CONFIG.lock().unwrap().is_hkdf_key_compressed
+    ECIES_CONFIG.read().is_hkdf_key_compressed
 }
diff --git a/src/lib.rs b/src/lib.rs
index 9333c26..85f4ec1 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,4 +1,11 @@
 #![doc = include_str!("../README.md")]
+#![no_std]
+
+#[cfg(feature = "std")]
+extern crate std;
+
+#[cfg(not(feature = "std"))]
+extern crate alloc;
 
 pub use libsecp256k1::{Error as SecpError, PublicKey, SecretKey};
 
@@ -11,10 +18,14 @@ pub mod symmetric;
 /// Utility functions
 pub mod utils;
 
+mod compat;
+
 use config::{get_ephemeral_key_size, is_ephemeral_key_compressed};
 use symmetric::{sym_decrypt, sym_encrypt};
 use utils::{decapsulate, encapsulate, generate_keypair};
 
+use crate::compat::Vec;
+
 /// Encrypt a message by a public key
 ///
 /// # Arguments
diff --git a/src/symmetric/mod.rs b/src/symmetric/mod.rs
index a5e0258..fe7b44f 100644
--- a/src/symmetric/mod.rs
+++ b/src/symmetric/mod.rs
@@ -12,6 +12,8 @@ use pure_aes::{decrypt, encrypt};
 #[cfg(feature = "xchacha20")]
 use xchacha20::{decrypt, encrypt};
 
+use crate::compat::Vec;
+
 /// Symmetric encryption wrapper. Openssl AES-256-GCM, pure Rust AES-256-GCM, or XChaCha20-Poly1305
 pub fn sym_encrypt(key: &[u8], msg: &[u8]) -> Option<Vec<u8>> {
     encrypt(key, msg)
@@ -25,7 +27,7 @@ pub fn sym_decrypt(key: &[u8], encrypted_msg: &[u8]) -> Option<Vec<u8>> {
 #[cfg(test)]
 pub(crate) mod tests {
     use hex::decode; // dev dep
-    use rand::{thread_rng, Rng};
+    use rand_core::{OsRng, RngCore};
 
     use super::*;
 
@@ -52,7 +54,7 @@ pub(crate) mod tests {
     fn test_random_key() {
         let text = b"this is a text";
         let mut key = [0u8; 32];
-        thread_rng().fill(&mut key);
+        OsRng.fill_bytes(&mut key);
 
         assert_eq!(
             text,
diff --git a/src/symmetric/openssl_aes.rs b/src/symmetric/openssl_aes.rs
index 6e8fa1f..9562038 100644
--- a/src/symmetric/openssl_aes.rs
+++ b/src/symmetric/openssl_aes.rs
@@ -1,7 +1,8 @@
 use openssl::symm::{decrypt_aead, encrypt_aead, Cipher};
-use rand::{thread_rng, Rng};
+use rand_core::{OsRng, RngCore};
 
 use crate::consts::{AEAD_TAG_LENGTH, AES_NONCE_LENGTH, EMPTY_BYTES};
+use crate::Vec;
 
 const NONCE_TAG_LENGTH: usize = AES_NONCE_LENGTH + AEAD_TAG_LENGTH;
 
@@ -10,7 +11,7 @@ pub fn encrypt(key: &[u8], msg: &[u8]) -> Option<Vec<u8>> {
     let cipher = Cipher::aes_256_gcm();
 
     let mut iv = [0u8; AES_NONCE_LENGTH];
-    thread_rng().fill(&mut iv);
+    OsRng.fill_bytes(&mut iv);
 
     let mut tag = [0u8; AEAD_TAG_LENGTH];
 
diff --git a/src/symmetric/pure_aes.rs b/src/symmetric/pure_aes.rs
index 9457dce..0ccbfd7 100644
--- a/src/symmetric/pure_aes.rs
+++ b/src/symmetric/pure_aes.rs
@@ -3,10 +3,11 @@ use aes_gcm::{
     aes::Aes256,
     AesGcm, KeyInit,
 };
-use rand::{thread_rng, Rng};
+use rand_core::{OsRng, RngCore};
 #[allow(unused_imports)]
 use typenum::consts::{U12, U16};
 
+use crate::compat::Vec;
 use crate::consts::{AEAD_TAG_LENGTH, AES_NONCE_LENGTH, EMPTY_BYTES};
 
 #[cfg(not(feature = "aes-12bytes-nonce"))]
@@ -23,7 +24,7 @@ pub fn encrypt(key: &[u8], msg: &[u8]) -> Option<Vec<u8>> {
     let aead = Aes256Gcm::new(key);
 
     let mut iv = [0u8; AES_NONCE_LENGTH];
-    thread_rng().fill(&mut iv);
+    OsRng.fill_bytes(&mut iv);
     let nonce = GenericArray::from_slice(&iv);
 
     let mut out = Vec::with_capacity(msg.len());
diff --git a/src/symmetric/xchacha20.rs b/src/symmetric/xchacha20.rs
index 850ebcf..0c1a5ee 100644
--- a/src/symmetric/xchacha20.rs
+++ b/src/symmetric/xchacha20.rs
@@ -2,8 +2,9 @@ use chacha20poly1305::{
     aead::{generic_array::GenericArray, AeadInPlace},
     KeyInit, XChaCha20Poly1305,
 };
-use rand::{thread_rng, Rng};
+use rand_core::{OsRng, RngCore};
 
+use crate::compat::Vec;
 use crate::consts::{AEAD_TAG_LENGTH, EMPTY_BYTES, XCHACHA20_NONCE_LENGTH};
 
 const NONCE_TAG_LENGTH: usize = XCHACHA20_NONCE_LENGTH + AEAD_TAG_LENGTH;
@@ -14,7 +15,7 @@ pub fn encrypt(key: &[u8], msg: &[u8]) -> Option<Vec<u8>> {
     let aead = XChaCha20Poly1305::new(key);
 
     let mut iv = [0u8; XCHACHA20_NONCE_LENGTH];
-    thread_rng().fill(&mut iv);
+    OsRng.fill_bytes(&mut iv);
     let nonce = GenericArray::from_slice(&iv);
 
     let mut out = Vec::with_capacity(msg.len());
diff --git a/src/utils.rs b/src/utils.rs
index 8ff186b..b3e456f 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -1,8 +1,9 @@
 use hkdf::Hkdf;
 use libsecp256k1::{Error as SecpError, PublicKey, SecretKey};
-use rand::thread_rng;
+use rand_core::OsRng;
 use sha2::Sha256;
 
+use crate::compat::Vec;
 use crate::config::{get_ephemeral_key_size, is_hkdf_key_compressed};
 use crate::consts::EMPTY_BYTES;
 
@@ -11,7 +12,7 @@ pub type SharedSecret = [u8; 32];
 
 /// Generate a `(SecretKey, PublicKey)` pair
 pub fn generate_keypair() -> (SecretKey, PublicKey) {
-    let sk = SecretKey::random(&mut thread_rng());
+    let sk = SecretKey::random(&mut OsRng);
     (sk, PublicKey::from_secret_key(&sk))
 }
 
diff --git a/tests/integration.rs b/tests/integration.rs
index c051323..e8f69df 100644
--- a/tests/integration.rs
+++ b/tests/integration.rs
@@ -8,8 +8,7 @@ use hex::decode;
 
 const MSG: &str = "helloworld🌍";
 
-#[test]
-fn can_change_behavior_with_config() {
+fn check_config_hkdf_key() {
     let mut two = [0u8; 32];
     let mut three = [0u8; 32];
     two[31] = 2u8;
@@ -25,34 +24,56 @@ fn can_change_behavior_with_config() {
         ..Config::default()
     });
 
-    assert_eq!(encapsulate(&sk2, &pk3), decapsulate(&pk2, &sk3));
+    let encapsulated = encapsulate(&sk2, &pk3).unwrap();
 
+    assert_eq!(encapsulated, decapsulate(&pk2, &sk3).unwrap());
     assert_eq!(
-        encapsulate(&sk2, &pk3).unwrap().to_vec(),
+        encapsulated.to_vec(),
         decode("b192b226edb3f02da11ef9c6ce4afe1c7e40be304e05ae3b988f4834b1cb6c69").unwrap()
     );
+}
+
+fn check_config_ephemeral_key() {
+    let (sk, pk) = generate_keypair();
+    let (sk, pk) = (&sk.serialize(), &pk.serialize_compressed());
+    let encrypted_1 = encrypt(pk, MSG.as_bytes()).unwrap();
+    assert_eq!(MSG.as_bytes(), decrypt(sk, &encrypted_1).unwrap().as_slice());
 
     update_config(Config {
         is_ephemeral_key_compressed: true,
-        is_hkdf_key_compressed: true,
+        ..Config::default()
     });
 
-    let (sk, pk) = generate_keypair();
-    let (sk, pk) = (&sk.serialize(), &pk.serialize_compressed());
-
-    assert_eq!(
-        MSG.as_bytes(),
-        decrypt(sk, &encrypt(pk, MSG.as_bytes()).unwrap()).unwrap().as_slice()
-    );
+    let encrypted_2 = encrypt(pk, MSG.as_bytes()).unwrap();
+    assert_eq!(encrypted_1.len() - encrypted_2.len(), 32);
+    assert_eq!(MSG.as_bytes(), decrypt(sk, &encrypted_2).unwrap().as_slice());
 
     reset_config();
 }
 
+#[test]
+fn can_change_behavior_with_config() {
+    check_config_hkdf_key();
+    check_config_ephemeral_key();
+}
+
+#[cfg(all(test, target_arch = "wasm32"))]
+mod wasm_tests {
+    use super::*;
+    use wasm_bindgen_test::*;
+
+    #[wasm_bindgen_test]
+    fn can_change_behavior_with_config() {
+        check_config_hkdf_key();
+        check_config_ephemeral_key();
+    }
+}
+
 #[test]
 #[cfg(all(
     not(target_arch = "wasm32"),
     not(feature = "aes-12bytes-nonce"),
-    not(feature = "xchacha20")
+    not(feature = "xchacha20"),
 ))]
 fn is_compatible_with_python() {
     use futures_util::FutureExt;