diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index dba55c0..20a016b 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -111,7 +111,7 @@ jobs:
   # Job 3: MSRV 验证（最低支持版本）
   # =============================================================================
   msrv:
-    name: MSRV (1.72.0)
+    name: MSRV (1.83.0)
     needs: lint
     runs-on: ubuntu-latest
     steps:
@@ -121,7 +121,7 @@ jobs:
       - name: 安装 MSRV 工具链
         uses: dtolnay/rust-toolchain@master
         with:
-          toolchain: "1.72.0"
+          toolchain: "1.83.0"
 
       - name: 缓存 Cargo 编译产物
         uses: Swatinem/rust-cache@v2
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 094d7da..9581e19 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -38,6 +38,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   - SM2 sign: 258 µs, verify: 316 µs
   - SM9 sign: 3.44 ms, verify: 5.50 ms
 
+### Changed
+
+- MSRV raised to 1.83.0 (required by crypto-bigint 0.6.x for ConstMontyForm constant-time Montgomery arithmetic)
+
 ### Security
 
 - GCM `gf128_mul`: replaced secret-dependent `if` branches with mask arithmetic
diff --git a/CHANGELOG.zh-CN.md b/CHANGELOG.zh-CN.md
index 8b599c6..b27d4bf 100644
--- a/CHANGELOG.zh-CN.md
+++ b/CHANGELOG.zh-CN.md
@@ -38,6 +38,10 @@
   - SM2 签名：258 µs，验签：316 µs
   - SM9 签名：3.44 ms，验签：5.50 ms
 
+### 变更
+
+- MSRV 提升至 1.83.0（crypto-bigint 0.6.x 的 ConstMontyForm 常量时间 Montgomery 算术所需）
+
 ### 安全
 
 - GCM `gf128_mul`：用掩码运算替换依赖秘密的 `if` 分支
diff --git a/Cargo.toml b/Cargo.toml
index 62dbc78..3786604 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -2,12 +2,12 @@
 name = "libsmx"
 version = "0.1.0"
 edition = "2021"
-rust-version = "1.72.0"
+rust-version = "1.83.0"
 license = "Apache-2.0"
 description = "Pure-Rust, no_std, constant-time SM2/SM3/SM4/SM9 Chinese cryptography (GB/T 32918/32905/32907/38635)"
-repository = "https://github.com/aspect-building/libsmx"
+repository = "https://github.com/kintaiW/libsmx"
 documentation = "https://docs.rs/libsmx"
-homepage = "https://github.com/aspect-building/libsmx"
+homepage = "https://github.com/kintaiW/libsmx"
 categories = ["cryptography", "no-std"]
 keywords = ["sm2", "sm3", "sm4", "sm9", "gmssl"]
 readme = "README.md"
diff --git a/README.md b/README.md
index e0c03f1..6d7e79d 100644
--- a/README.md
+++ b/README.md
@@ -5,7 +5,7 @@
 [![docs.rs](https://img.shields.io/docsrs/libsmx)](https://docs.rs/libsmx)
 [![codecov](https://codecov.io/gh/kintaiW/libsmx/graph/badge.svg)](https://codecov.io/gh/kintaiW/libsmx)
 [![License](https://img.shields.io/crates/l/libsmx.svg)](LICENSE)
-[![MSRV](https://img.shields.io/badge/MSRV-1.72.0-blue.svg)](https://blog.rust-lang.org/2023/08/24/Rust-1.72.0.html)
+[![MSRV](https://img.shields.io/badge/MSRV-1.83.0-blue.svg)](https://blog.rust-lang.org/2024/11/28/Rust-1.83.0.html)
 
 Pure-Rust, `#![no_std]` implementation of Chinese commercial cryptography standards with constant-time operations throughout.
 
@@ -211,7 +211,7 @@ cargo bench
 
 ## MSRV Policy
 
-The minimum supported Rust version is **1.72.0**. MSRV bumps are treated as minor version changes.
+The minimum supported Rust version is **1.83.0**. MSRV bumps are treated as minor version changes.
 
 ## License
 
diff --git a/README.zh-CN.md b/README.zh-CN.md
index b57570e..a1801f5 100644
--- a/README.zh-CN.md
+++ b/README.zh-CN.md
@@ -5,7 +5,7 @@
 [![docs.rs](https://img.shields.io/docsrs/libsmx)](https://docs.rs/libsmx)
 [![codecov](https://codecov.io/gh/kintaiW/libsmx/graph/badge.svg)](https://codecov.io/gh/kintaiW/libsmx)
 [![License](https://img.shields.io/crates/l/libsmx.svg)](LICENSE)
-[![MSRV](https://img.shields.io/badge/MSRV-1.72.0-blue.svg)](https://blog.rust-lang.org/2023/08/24/Rust-1.72.0.html)
+[![MSRV](https://img.shields.io/badge/MSRV-1.83.0-blue.svg)](https://blog.rust-lang.org/2024/11/28/Rust-1.83.0.html)
 
 纯 Rust、`#![no_std]` 实现的中国商用密码算法库，全程常量时间操作。
 
@@ -246,7 +246,7 @@ cargo bench
 
 ## 最低支持 Rust 版本（MSRV）
 
-最低支持版本为 **Rust 1.72.0**。MSRV 提升视为次版本号变更。
+最低支持版本为 **Rust 1.83.0**。MSRV 提升视为次版本号变更。
 
 ## 许可证
 
diff --git a/src/sm3/mod.rs b/src/sm3/mod.rs
index 1974c3c..0c621c0 100644
--- a/src/sm3/mod.rs
+++ b/src/sm3/mod.rs
@@ -265,11 +265,22 @@ mod tests {
     // 辅助：从十六进制字符串构造 [u8; 32]
     fn hex_literal(s: &str) -> [u8; 32] {
         let mut out = [0u8; 32];
-        let bytes: alloc::vec::Vec<u8> = (0..s.len())
-            .step_by(2)
-            .map(|i| u8::from_str_radix(&s[i..i + 2], 16).unwrap())
-            .collect();
-        out.copy_from_slice(&bytes);
+        let b = s.as_bytes();
+        for i in 0..32 {
+            let hi = match b[i * 2] {
+                c @ b'0'..=b'9' => c - b'0',
+                c @ b'a'..=b'f' => c - b'a' + 10,
+                c @ b'A'..=b'F' => c - b'A' + 10,
+                _ => panic!("invalid hex"),
+            };
+            let lo = match b[i * 2 + 1] {
+                c @ b'0'..=b'9' => c - b'0',
+                c @ b'a'..=b'f' => c - b'a' + 10,
+                c @ b'A'..=b'F' => c - b'A' + 10,
+                _ => panic!("invalid hex"),
+            };
+            out[i] = hi << 4 | lo;
+        }
         out
     }
 }
diff --git a/src/sm4/modes.rs b/src/sm4/modes.rs
index 9bf1e97..9290a80 100644
--- a/src/sm4/modes.rs
+++ b/src/sm4/modes.rs
@@ -654,6 +654,7 @@ pub fn sm4_decrypt_xts(
 // ── 测试 ──────────────────────────────────────────────────────────────────────
 
 #[cfg(test)]
+#[cfg(feature = "alloc")]
 mod tests {
     use super::*;