diff --git a/src/cookbook/cryptography/encryption.md b/src/cookbook/cryptography/encryption.md
index a728da46..becab266 100644
--- a/src/cookbook/cryptography/encryption.md
+++ b/src/cookbook/cryptography/encryption.md
@@ -1,7 +1,7 @@
 # 加密
 
 ### 使用  PBKDF2 对密码进行哈希和加盐( salt )
-[ring::pbkdf2]() 可以对一个加盐密码进行哈希。
+[ring::pbkdf2](https://briansmith.org/rustdoc/ring/pbkdf2/index.html) 可以对一个加盐密码进行哈希。
 
 ```rust,editable
 
diff --git a/src/cookbook/datastructures/bitfield.md b/src/cookbook/datastructures/bitfield.md
index 7f16f82f..4c9c29e0 100644
--- a/src/cookbook/datastructures/bitfield.md
+++ b/src/cookbook/datastructures/bitfield.md
@@ -1 +1,47 @@
 # 位字段
+
+### 定义和操作位字段
+使用 [`bitflags!`](https://docs.rs/bitflags/1.3.2/bitflags/macro.bitflags.html) 宏可以帮助我们创建安全的位字段类型 `MyFlags`，然后为其实现基本的 `clear` 操作。以下代码展示了基本的位操作和格式化:
+```rust,editable
+use bitflags::bitflags;
+use std::fmt;
+
+bitflags! {
+    struct MyFlags: u32 {
+        const FLAG_A       = 0b00000001;
+        const FLAG_B       = 0b00000010;
+        const FLAG_C       = 0b00000100;
+        const FLAG_ABC     = Self::FLAG_A.bits
+                           | Self::FLAG_B.bits
+                           | Self::FLAG_C.bits;
+    }
+}
+
+impl MyFlags {
+    pub fn clear(&mut self) -> &mut MyFlags {
+        self.bits = 0;  
+        self
+    }
+}
+
+impl fmt::Display for MyFlags {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{:032b}", self.bits)
+    }
+}
+
+fn main() {
+    let e1 = MyFlags::FLAG_A | MyFlags::FLAG_C;
+    let e2 = MyFlags::FLAG_B | MyFlags::FLAG_C;
+    assert_eq!((e1 | e2), MyFlags::FLAG_ABC);   
+    assert_eq!((e1 & e2), MyFlags::FLAG_C);    
+    assert_eq!((e1 - e2), MyFlags::FLAG_A);    
+    assert_eq!(!e2, MyFlags::FLAG_A);           
+
+    let mut flags = MyFlags::FLAG_ABC;
+    assert_eq!(format!("{}", flags), "00000000000000000000000000000111");
+    assert_eq!(format!("{}", flags.clear()), "00000000000000000000000000000000");
+    assert_eq!(format!("{:?}", MyFlags::FLAG_B), "FLAG_B");
+    assert_eq!(format!("{:?}", MyFlags::FLAG_A | MyFlags::FLAG_B), "FLAG_A | FLAG_B");
+}
+```
\ No newline at end of file
diff --git a/内容变更记录.md b/内容变更记录.md
index 4b301d2c..af513259 100644
--- a/内容变更记录.md
+++ b/内容变更记录.md
@@ -4,6 +4,8 @@
 ## 2022-04-04 
 
 - 新增章节: [Cookbook - 使用 rayon 并行处理数据](https://course.rs/cookbook/cocurrency/parallel.html)
+- 新增章节： [Cookbook - 加密](https://course.rs/cookbook/cryptography/encryption.html)
+- 新增章节： [Cookbook - 哈希](https://course.rs/cookbook/cryptography/hashing.html)
 
 
 ## 2022-04-03