Start with challenge 18.

src/ctr.rs

@@ -0,0 +1,37 @@
+use crate::bytes::Bytes;
+// use crate::cbc;
+// use openssl::symm;
+
+fn _xor(a: &[u8], b: &[u8]) -> Vec<u8> {
+    Iterator::zip(a.iter(), b.iter())
+        .map(|z| *(z.0) ^ *(z.1))
+        .collect()
+}
+
+pub fn _encrypt(Bytes(_key): &Bytes, Bytes(_data): &Bytes) -> Bytes {
+    // let block_size = 16;
+    let result: Vec<u8> = vec![];
+    // let mut prev_cipher: Vec<u8> = iv.to_vec(); // first xor input is IV
+    // for data in data.chunks(block_size) {
+    //     let xored = xor(&prev_cipher, data);
+    //     let mut cipher = cbc::enrypt_aes_128_ecb_block(key, &xored);
+    //     prev_cipher = cipher.to_vec(); // cipher is input for next xor
+    //     result.append(&mut cipher);
+    // }
+    Bytes(result)
+}
+
+pub fn decrypt(Bytes(_key): &Bytes, Bytes(_data): &Bytes) -> Bytes {
+    // XXX: does not handle padding for last block
+    // let cipher_type = symm::Cipher::aes_128_ecb();
+    // let block_size = cipher_type.block_size();
+    let result: Vec<u8> = vec![];
+    // let mut prev_cipher: Vec<u8> = iv.to_vec(); // first xor input is IV
+    // for cipher in data.chunks(block_size) {
+    //     let xored = cbc::decrypt_aes_128_ecb_block(key, &cipher);
+    //     let data = xor(&xored, &prev_cipher);
+    //     result.extend(data.to_vec());
+    //     prev_cipher = cipher.to_vec();
+    // }
+    Bytes(result)
+}