problem 25

1 files changed, 50 insertions, 0 deletions

diff --git a/tests/set4.rs b/tests/set4.rs
new file mode 100644
index 0000000..3967f85
--- /dev/null
+++ b/tests/set4.rs
@@ -0,0 +1,50 @@
+extern crate matasano;
+extern crate rand;
+
+use rand::Rng;
+
+mod util;
+
+#[test]
+fn problem_25 () {
+    let key = util::random_aes_128_key();
+    let nonce: u64 = rand::thread_rng().gen();
+    let plaintext = util::read("data/25.txt");
+
+    let ciphertext = matasano::aes_128_ctr(&plaintext[..], &key[..], nonce);
+    let edit = |ciphertext: &[u8], offset: usize, newtext: &[u8]| {
+        let block_start_number = offset / 16;
+        let block_start = block_start_number * 16;
+        let block_end_number = (offset + newtext.len() - 1) / 16;
+        let block_end = std::cmp::min(
+            (block_end_number + 1) * 16,
+            ciphertext.len()
+        );
+        let mut plaintext = matasano::aes_128_ctr_with_counter(
+            &ciphertext[block_start..block_end],
+            &key[..],
+            nonce,
+            (offset / 16) as u64
+        );
+        for i in 0..newtext.len() {
+            plaintext[offset - block_start + i] = newtext[i];
+        }
+        let new_ciphertext = matasano::aes_128_ctr_with_counter(
+            &plaintext[..],
+            &key[..],
+            nonce,
+            (offset / 16) as u64
+        );
+
+        return ciphertext
+            .iter()
+            .take(block_start)
+            .chain(new_ciphertext.iter())
+            .chain(ciphertext.iter().skip(block_end))
+            .map(|x| *x)
+            .collect();
+    };
+
+    let got = matasano::crack_aes_128_ctr_random_access(&ciphertext[..], edit);
+    assert_eq!(&got[..], &plaintext[..]);
+}