move submodules in-tree

blog/helpers/ciphertext-tampering/src/main.rs

@@ -0,0 +1,39 @@
+//! ```toml
+//! [dependencies]
+//! chacha20 = "0.9.1"
+//! ````
+
+use chacha20::cipher::{KeyIvInit, StreamCipher};
+
+fn main() {
+    let key: chacha20::Key = [
+        0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 19, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
+        25, 26, 27, 28, 29, 30, 31,
+    ]
+    .into();
+    let mut cipher = chacha20::ChaCha20::new(&key, &[0; 12].into());
+
+    // Encrypt
+    let plaintext = "ls -l /etc";
+    eprintln!("plaintext:    {:?}", plaintext);
+    let mut plaintext = plaintext.as_bytes().to_vec();
+    eprintln!("plaintext:    {:x?}", plaintext);
+    cipher.apply_keystream(&mut plaintext);
+    eprintln!("ciphertext:   {:x?}", plaintext);
+
+    // Flipping
+    flip_it(&mut plaintext);
+    eprintln!("ciphertext 2: {:x?}", plaintext);
+
+    // Decrypt
+    let mut cipher = chacha20::ChaCha20::new(&key, &[0; 12].into());
+    cipher.apply_keystream(&mut plaintext);
+    eprintln!("plaintext 2:  {:x?}", plaintext);
+    eprintln!("plaintext 2:  {:x?}", String::from_utf8(plaintext).unwrap());
+}
+
+fn flip_it(ciphertext: &mut [u8]) {
+    ciphertext[0] ^= 0b0001_1110;
+    ciphertext[1] ^= 0b0001_1110;
+    ciphertext[4] ^= 0b0001_1110;
+}