Solve challenge 19

data/set3/challenge19.txt

@@ -0,0 +1,40 @@
+SSBoYXZlIG1ldCB0aGVtIGF0IGNsb3NlIG9mIGRheQ==
+Q29taW5nIHdpdGggdml2aWQgZmFjZXM=
+RnJvbSBjb3VudGVyIG9yIGRlc2sgYW1vbmcgZ3JleQ==
+RWlnaHRlZW50aC1jZW50dXJ5IGhvdXNlcy4=
+SSBoYXZlIHBhc3NlZCB3aXRoIGEgbm9kIG9mIHRoZSBoZWFk
+T3IgcG9saXRlIG1lYW5pbmdsZXNzIHdvcmRzLA==
+T3IgaGF2ZSBsaW5nZXJlZCBhd2hpbGUgYW5kIHNhaWQ=
+UG9saXRlIG1lYW5pbmdsZXNzIHdvcmRzLA==
+QW5kIHRob3VnaHQgYmVmb3JlIEkgaGFkIGRvbmU=
+T2YgYSBtb2NraW5nIHRhbGUgb3IgYSBnaWJl
+VG8gcGxlYXNlIGEgY29tcGFuaW9u
+QXJvdW5kIHRoZSBmaXJlIGF0IHRoZSBjbHViLA==
+QmVpbmcgY2VydGFpbiB0aGF0IHRoZXkgYW5kIEk=
+QnV0IGxpdmVkIHdoZXJlIG1vdGxleSBpcyB3b3JuOg==
+QWxsIGNoYW5nZWQsIGNoYW5nZWQgdXR0ZXJseTo=
+QSB0ZXJyaWJsZSBiZWF1dHkgaXMgYm9ybi4=
+VGhhdCB3b21hbidzIGRheXMgd2VyZSBzcGVudA==
+SW4gaWdub3JhbnQgZ29vZCB3aWxsLA==
+SGVyIG5pZ2h0cyBpbiBhcmd1bWVudA==
+VW50aWwgaGVyIHZvaWNlIGdyZXcgc2hyaWxsLg==
+V2hhdCB2b2ljZSBtb3JlIHN3ZWV0IHRoYW4gaGVycw==
+V2hlbiB5b3VuZyBhbmQgYmVhdXRpZnVsLA==
+U2hlIHJvZGUgdG8gaGFycmllcnM/
+VGhpcyBtYW4gaGFkIGtlcHQgYSBzY2hvb2w=
+QW5kIHJvZGUgb3VyIHdpbmdlZCBob3JzZS4=
+VGhpcyBvdGhlciBoaXMgaGVscGVyIGFuZCBmcmllbmQ=
+V2FzIGNvbWluZyBpbnRvIGhpcyBmb3JjZTs=
+SGUgbWlnaHQgaGF2ZSB3b24gZmFtZSBpbiB0aGUgZW5kLA==
+U28gc2Vuc2l0aXZlIGhpcyBuYXR1cmUgc2VlbWVkLA==
+U28gZGFyaW5nIGFuZCBzd2VldCBoaXMgdGhvdWdodC4=
+VGhpcyBvdGhlciBtYW4gSSBoYWQgZHJlYW1lZA==
+QSBkcnVua2VuLCB2YWluLWdsb3Jpb3VzIGxvdXQu
+SGUgaGFkIGRvbmUgbW9zdCBiaXR0ZXIgd3Jvbmc=
+VG8gc29tZSB3aG8gYXJlIG5lYXIgbXkgaGVhcnQs
+WWV0IEkgbnVtYmVyIGhpbSBpbiB0aGUgc29uZzs=
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+VHJhbnNmb3JtZWQgdXR0ZXJseTo=
+QSB0ZXJyaWJsZSBiZWF1dHkgaXMgYm9ybi4=

src/set1.rs

@@ -45,7 +45,7 @@ lazy_static! {
     };
 }
 
-fn xor_cross_entropy_analysis(encoded: &[u8]) -> (u8, f64) {
+pub fn xor_cross_entropy_analysis(encoded: &[u8]) -> (u8, f64) {
     let mut min_cross_entropy = f64::MAX;
     let mut best_key = 0;
     for key in 0..=255 {

src/set3.rs

@@ -1,4 +1,10 @@
-use crate::{cbc::*, ctr::aes128_ctr_decrypt, ecb::*, utils::{conversions::base64_to_raw, io::*}};
+use crate::{
+    cbc::*,
+    ctr::aes128_ctr_decrypt,
+    ecb::*,
+    set1::xor_cross_entropy_analysis,
+    utils::{conversions::base64_to_raw, io::*},
+};
 use lazy_static::lazy_static;
 use rand::{Rng, SeedableRng};
 
@@ -139,8 +145,32 @@ fn challange17() {
 
 #[test]
 fn challange18() {
-    let ciphertext = base64_to_raw("L77na/nrFsKvynd6HzOoG7GHTLXsTVu9qvY/2syLXzhPweyyMTJULu/6/kXX0KSvoOLSFQ==");
+    let ciphertext =
+        base64_to_raw("L77na/nrFsKvynd6HzOoG7GHTLXsTVu9qvY/2syLXzhPweyyMTJULu/6/kXX0KSvoOLSFQ==");
     let key = b"YELLOW SUBMARINE";
     let plaintext = aes128_ctr_decrypt(&ciphertext, key, 0, 0);
     assert!(String::from_utf8_lossy(&plaintext).contains("Ice, Ice, baby"));
 }
+
+#[test]
+fn challange19() {
+    let ciphertexts = read_base64_lines("data/set3/challenge19.txt");
+    let mut plaintexts = vec![Vec::new(); ciphertexts.len()];
+    let len = ciphertexts.iter().map(|c| c.len()).max().unwrap();
+    for idx in 0..len {
+        let cipher_bytes: Vec<u8> = ciphertexts
+            .iter()
+            .filter_map(|c| c.get(idx))
+            .map(|&x| x)
+            .collect();
+        let (key, _) = xor_cross_entropy_analysis(&cipher_bytes);
+        for (i, plaintext) in plaintexts.iter_mut().enumerate() {
+            if let Some(byte) = ciphertexts[i].get(idx) {
+                plaintext.push(byte ^ key);
+            }
+        }
+    }
+    assert!(String::from_utf8_lossy(&plaintexts[5]).contains("polite meaningless words"));
+    assert!(String::from_utf8_lossy(&plaintexts[34]).contains("yet I number him in the song"));
+    // doesn't decode all the way correctly but gets the bulk of the job done
+}