stage

problems/p4/src/main.rs

@@ -0,0 +1,26 @@
+use common::is_valid_english;
+use std::error::Error;
+use std::fs;
+
+fn main() -> Result<(), Box<dyn Error>> {
+    let ciphers = fs::read_to_string("./problems/p4/4.txt")?;
+    let cipher: String = ciphers.lines().collect();
+
+    let cipher_bytes = hex::decode(cipher).expect("decode error");
+    let window_size = 20;
+    for key in 0..(1 << 8) {
+        let key: u8 = key as u8;
+        // 对密文的每个字节应用异或操作，得到明文
+        let plaintext: Vec<u8> = cipher_bytes.iter().map(|&byte| byte ^ key).collect();
+        for i in 0..=(plaintext.iter().len() - window_size) {
+            if let Ok(text) = std::str::from_utf8(&plaintext[i..i + window_size]) {
+                if is_valid_english(text, None) {
+                    println!("Found valid sentence with key {key}: {}", text);
+                }
+            }
+        }
+        // 尝试将字节转换为字符串
+    }
+
+    Ok(())
+}