diff --git a/.idea/lib_um_crypto.iml b/.idea/lib_um_crypto.iml
index aeb88fa..beec96a 100644
--- a/.idea/lib_um_crypto.iml
+++ b/.idea/lib_um_crypto.iml
@@ -5,6 +5,7 @@
       <sourceFolder url="file://$MODULE_DIR$/um_wasm/src" isTestSource="false" />
       <sourceFolder url="file://$MODULE_DIR$/um_wasm/tests" isTestSource="true" />
       <sourceFolder url="file://$MODULE_DIR$/um_crypto/kuwo/src" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/um_crypto/qmc/src" isTestSource="false" />
       <excludeFolder url="file://$MODULE_DIR$/target" />
     </content>
     <orderEntry type="inheritedJdk" />
diff --git a/Cargo.lock b/Cargo.lock
index 04b7a04..040b006 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -168,6 +168,7 @@ dependencies = [
  "anyhow",
  "console_error_panic_hook",
  "umc_kuwo",
+ "umc_qmc",
  "wasm-bindgen",
  "wasm-bindgen-test",
 ]
@@ -182,6 +183,16 @@ dependencies = [
  "thiserror",
 ]
 
+[[package]]
+name = "umc_qmc"
+version = "0.1.0"
+dependencies = [
+ "anyhow",
+ "base64",
+ "itertools",
+ "thiserror",
+]
+
 [[package]]
 name = "unicode-ident"
 version = "1.0.12"
diff --git a/Cargo.toml b/Cargo.toml
index f7c94cb..a31b498 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,3 +1,7 @@
 [workspace]
 resolver = "2"
 members = ["um_crypto/*", "um_wasm"]
+
+[profile.release.package.um_wasm]
+# Tell `rustc` to optimize for small code size.
+opt-level = "s"
diff --git a/um_crypto/qmc/Cargo.toml b/um_crypto/qmc/Cargo.toml
new file mode 100644
index 0000000..70caf28
--- /dev/null
+++ b/um_crypto/qmc/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "umc_qmc"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+base64 = "0.22.1"
+itertools = "0.13.0"
+anyhow = "1.0.86"
+thiserror = "1.0.63"
diff --git a/um_crypto/qmc/src/lib.rs b/um_crypto/qmc/src/lib.rs
new file mode 100644
index 0000000..65864b6
--- /dev/null
+++ b/um_crypto/qmc/src/lib.rs
@@ -0,0 +1,7 @@
+use thiserror::Error;
+
+pub mod v1;
+pub mod v2_rc4;
+
+#[derive(Error, Debug)]
+pub enum QmcCryptoError {}
diff --git a/um_crypto/qmc/src/v1/cipher.rs b/um_crypto/qmc/src/v1/cipher.rs
new file mode 100644
index 0000000..363142f
--- /dev/null
+++ b/um_crypto/qmc/src/v1/cipher.rs
@@ -0,0 +1,14 @@
+const V1_OFFSET_BOUNDARY: usize = 0x7FFF;
+
+pub const V1_KEY_SIZE: usize = 128;
+
+#[inline]
+pub fn qmc1_transform(key: &[u8; V1_KEY_SIZE], value: u8, offset: usize) -> u8 {
+    let offset = match offset {
+        0..V1_OFFSET_BOUNDARY => offset,
+        V1_OFFSET_BOUNDARY => V1_OFFSET_BOUNDARY,
+        offset => offset % V1_OFFSET_BOUNDARY,
+    };
+
+    value ^ key[offset % V1_KEY_SIZE]
+}
diff --git a/um_crypto/qmc/src/v1/mod.rs b/um_crypto/qmc/src/v1/mod.rs
new file mode 100644
index 0000000..60e989a
--- /dev/null
+++ b/um_crypto/qmc/src/v1/mod.rs
@@ -0,0 +1,26 @@
+pub mod cipher;
+use cipher::{qmc1_transform, V1_KEY_SIZE};
+
+const V1_STATIC_KEY: [u8; V1_KEY_SIZE] = [
+    0xc3, 0x4a, 0xd6, 0xca, 0x90, 0x67, 0xf7, 0x52, 0xd8, 0xa1, 0x66, 0x62, 0x9f, 0x5b, 0x09, 0x00,
+    0xc3, 0x5e, 0x95, 0x23, 0x9f, 0x13, 0x11, 0x7e, 0xd8, 0x92, 0x3f, 0xbc, 0x90, 0xbb, 0x74, 0x0e,
+    0xc3, 0x47, 0x74, 0x3d, 0x90, 0xaa, 0x3f, 0x51, 0xd8, 0xf4, 0x11, 0x84, 0x9f, 0xde, 0x95, 0x1d,
+    0xc3, 0xc6, 0x09, 0xd5, 0x9f, 0xfa, 0x66, 0xf9, 0xd8, 0xf0, 0xf7, 0xa0, 0x90, 0xa1, 0xd6, 0xf3,
+    0xc3, 0xf3, 0xd6, 0xa1, 0x90, 0xa0, 0xf7, 0xf0, 0xd8, 0xf9, 0x66, 0xfa, 0x9f, 0xd5, 0x09, 0xc6,
+    0xc3, 0x1d, 0x95, 0xde, 0x9f, 0x84, 0x11, 0xf4, 0xd8, 0x51, 0x3f, 0xaa, 0x90, 0x3d, 0x74, 0x47,
+    0xc3, 0x0e, 0x74, 0xbb, 0x90, 0xbc, 0x3f, 0x92, 0xd8, 0x7e, 0x11, 0x13, 0x9f, 0x23, 0x95, 0x5e,
+    0xc3, 0x00, 0x09, 0x5b, 0x9f, 0x62, 0x66, 0xa1, 0xd8, 0x52, 0xf7, 0x67, 0x90, 0xca, 0xd6, 0x4a,
+];
+
+pub fn decrypt(data: &mut [u8], offset: usize) {
+    for (i, datum) in data.iter_mut().enumerate() {
+        *datum = qmc1_transform(&V1_STATIC_KEY, *datum, offset + i);
+    }
+}
+
+#[test]
+fn test_decryption() {
+    let mut data = *b"\xab\x2f\xba\xa6\xff\x47\x80\x3d\xaa\xcd\x02";
+    decrypt(&mut data, 0);
+    assert_eq!(data, *b"hello world");
+}
diff --git a/um_crypto/qmc/src/v2_rc4/cipher.rs b/um_crypto/qmc/src/v2_rc4/cipher.rs
new file mode 100644
index 0000000..43fdd51
--- /dev/null
+++ b/um_crypto/qmc/src/v2_rc4/cipher.rs
@@ -0,0 +1,86 @@
+use crate::v2_rc4::hash::hash;
+use crate::v2_rc4::rc4::RC4;
+use crate::v2_rc4::segment_key::get_segment_key;
+use std::cmp::min;
+
+const FIRST_SEGMENT_SIZE: usize = 0x0080;
+const OTHER_SEGMENT_SIZE: usize = 0x1400;
+const RC4_STREAM_CACHE_SIZE: usize = OTHER_SEGMENT_SIZE + 512;
+
+#[derive(Debug, Clone)]
+pub struct QMC2RC4 {
+    hash: f64,
+    key: Box<[u8]>,
+    key_stream: [u8; RC4_STREAM_CACHE_SIZE],
+}
+
+impl QMC2RC4 {
+    pub fn new(key: &[u8]) -> Self {
+        let mut rc4 = RC4::new(key);
+        let mut key_stream = [0u8; RC4_STREAM_CACHE_SIZE];
+        rc4.derive(&mut key_stream);
+
+        Self {
+            hash: hash(key),
+            key: key.into(),
+            key_stream,
+        }
+    }
+
+    fn transform_first_segment(&mut self, offset: usize, dst: &mut [u8]) {
+        let n = self.key.len();
+
+        for (value, offset) in dst.iter_mut().zip(offset..) {
+            let idx = get_segment_key(offset as u64, self.key[offset % n], self.hash);
+            *value ^= self.key[idx % n];
+        }
+    }
+
+    fn transform_other_segment(&mut self, offset: usize, data: &mut [u8]) {
+        let n = self.key.len();
+
+        let id = offset / OTHER_SEGMENT_SIZE;
+        let block_offset = offset % OTHER_SEGMENT_SIZE;
+
+        let skip = get_segment_key(id as u64, self.key[block_offset % n], self.hash);
+
+        debug_assert!(data.len() <= OTHER_SEGMENT_SIZE - block_offset);
+        let key_stream = self.key_stream.iter().skip(skip + block_offset);
+        for (datum, &key) in data.iter_mut().zip(key_stream) {
+            *datum ^= key;
+        }
+    }
+
+    pub fn transform(&mut self, start_offset: usize, data: &mut [u8]) {
+        let mut offset = start_offset;
+        let mut buffer = data;
+        if offset < FIRST_SEGMENT_SIZE {
+            let n = min(FIRST_SEGMENT_SIZE - offset, buffer.len());
+            let (block, rest) = buffer.split_at_mut(n);
+            buffer = rest;
+            self.transform_first_segment(offset, block);
+            offset += n;
+        }
+
+        match offset % OTHER_SEGMENT_SIZE {
+            0 => {} // we are already in the boundary, nothing to do.
+            excess => {
+                let n = min(OTHER_SEGMENT_SIZE - excess, buffer.len());
+                let (block, rest) = buffer.split_at_mut(n);
+                buffer = rest;
+                self.transform_other_segment(offset, block);
+                offset += n;
+            }
+        };
+
+        while !buffer.is_empty() {
+            let n = min(OTHER_SEGMENT_SIZE, buffer.len());
+            let (block, rest) = buffer.split_at_mut(n);
+            buffer = rest;
+            self.transform_other_segment(offset, block);
+            offset += n;
+        }
+    }
+}
+
+// TODO: Add tests here
diff --git a/um_crypto/qmc/src/v2_rc4/hash.rs b/um_crypto/qmc/src/v2_rc4/hash.rs
new file mode 100644
index 0000000..e7b39e8
--- /dev/null
+++ b/um_crypto/qmc/src/v2_rc4/hash.rs
@@ -0,0 +1,24 @@
+pub fn hash<T: AsRef<[u8]>>(key: T) -> f64 {
+    let mut hash = 1u32;
+    for &v in key.as_ref().iter() {
+        if v == 0 {
+            continue;
+        }
+
+        let next_hash = hash.wrapping_mul(v as u32);
+        if next_hash == 0 || next_hash <= hash {
+            break;
+        }
+
+        hash = next_hash;
+    }
+
+    hash.into()
+}
+
+#[test]
+fn test_hash() {
+    let expected = 4045008896.0;
+    let actual = hash(b"hello world");
+    assert_eq!(expected, actual);
+}
diff --git a/um_crypto/qmc/src/v2_rc4/mod.rs b/um_crypto/qmc/src/v2_rc4/mod.rs
new file mode 100644
index 0000000..d40c93e
--- /dev/null
+++ b/um_crypto/qmc/src/v2_rc4/mod.rs
@@ -0,0 +1,4 @@
+pub mod cipher;
+pub mod hash;
+pub mod rc4;
+pub mod segment_key;
diff --git a/um_crypto/qmc/src/v2_rc4/rc4.rs b/um_crypto/qmc/src/v2_rc4/rc4.rs
new file mode 100644
index 0000000..c7724e1
--- /dev/null
+++ b/um_crypto/qmc/src/v2_rc4/rc4.rs
@@ -0,0 +1,62 @@
+use std::ops::Rem;
+
+#[derive(Debug, Clone)]
+pub struct RC4 {
+    state: Box<[u8]>,
+    i: usize,
+    j: usize,
+}
+
+fn init_state(key: &[u8]) -> Box<[u8]> {
+    let n = key.len();
+    let mut state: Box<[u8]> = (0..n).map(|i| i as u8).collect();
+
+    let mut j = 0usize;
+    for i in 0..state.len() {
+        j = (j + usize::from(state[i]) + usize::from(key[i % n])) % n;
+        state.swap(i, j);
+    }
+
+    state
+}
+
+impl RC4 {
+    pub fn new<K: AsRef<[u8]>>(key: K) -> Self {
+        Self {
+            state: init_state(key.as_ref()),
+            i: 0,
+            j: 0,
+        }
+    }
+
+    pub fn generate(&mut self) -> u8 {
+        let n = self.state.len();
+        self.i = self.i.wrapping_add(1).rem(n);
+        self.j = self.j.wrapping_add(self.state[self.i].into()).rem(n);
+        self.state.swap(self.i, self.j);
+
+        let i = usize::from(self.state[self.i]);
+        let j = usize::from(self.state[self.j]);
+        let index = (i + j) % n;
+
+        self.state[index]
+    }
+
+    pub fn derive(&mut self, buffer: &mut [u8]) {
+        for item in buffer.iter_mut() {
+            *item ^= self.generate();
+        }
+    }
+}
+
+#[test]
+fn test_rc4() {
+    let mut rc4 = RC4::new(b"this is a test key");
+    let rc4_copy = rc4.clone();
+
+    let mut data = *b"hello world";
+    rc4.derive(&mut data[..]);
+
+    assert_ne!(rc4.state, rc4_copy.state);
+    assert_eq!(&data, b"\x68\x75\x6b\x64\x64\x24\x7f\x60\x7c\x7d\x60")
+}
diff --git a/um_crypto/qmc/src/v2_rc4/segment_key.rs b/um_crypto/qmc/src/v2_rc4/segment_key.rs
new file mode 100644
index 0000000..b4ed76b
--- /dev/null
+++ b/um_crypto/qmc/src/v2_rc4/segment_key.rs
@@ -0,0 +1,24 @@
+pub fn get_segment_key(id: u64, seed: u8, hash: f64) -> usize {
+    match seed {
+        0 => 0,
+        seed => {
+            let result = hash / ((id + 1).wrapping_mul(seed.into()) as f64) * 100.0;
+            result as usize
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_segment_key_nil_seed() {
+        assert_eq!(get_segment_key(1, 0, 12345.0), 0);
+    }
+
+    #[test]
+    fn test_segment_key_123() {
+        assert_eq!(get_segment_key(1, 123, 12345.0), 5018);
+    }
+}
diff --git a/um_wasm/Cargo.toml b/um_wasm/Cargo.toml
index 300ba65..5c84bf0 100644
--- a/um_wasm/Cargo.toml
+++ b/um_wasm/Cargo.toml
@@ -23,10 +23,7 @@ anyhow = "1.0.86"
 # code size when deploying.
 console_error_panic_hook = { version = "0.1.7", optional = true }
 umc_kuwo = { path = "../um_crypto/kuwo" }
+umc_qmc = { path = "../um_crypto/qmc" }
 
 [dev-dependencies]
 wasm-bindgen-test = "0.3.34"
-
-[profile.release]
-# Tell `rustc` to optimize for small code size.
-opt-level = "s"