problem 24 part 2

3 files changed, 23 insertions, 0 deletions

diff --git a/src/crack.rs b/src/crack.rs
index 396eb6b..39a8e1a 100644
--- a/src/crack.rs
+++ b/src/crack.rs
@@ -414,6 +414,19 @@ pub fn recover_16_bit_mt19937_key (ciphertext: &[u8], suffix: &[u8]) -> Option<u
     return None;
 }
 
+pub fn recover_mt19937_key_from_time (token: &[u8]) -> Option<u32> {
+    let now = ::time::now().to_timespec().sec as u32;
+    for i in -500..500i32 {
+        let seed = (now as i32).wrapping_add(i) as u32;
+        let mut mt = MersenneTwister::from_seed(seed);
+        let test_token: Vec<u8> = mt.gen_iter().take(16).collect();
+        if &test_token[..] == token {
+            return Some(seed);
+        }
+    }
+    return None;
+}
+
 fn crack_single_byte_xor_with_confidence (input: &[u8]) -> (u8, f64) {
     let mut min_diff = 100.0;
     let mut best_key = 0;
diff --git a/src/lib.rs b/src/lib.rs
index 21bac75..eeb3278 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -40,3 +40,4 @@ pub use crack::crack_fixed_nonce_ctr_statistically;
 pub use crack::recover_mersenne_twister_seed_from_time;
 pub use crack::clone_mersenne_twister_from_output;
 pub use crack::recover_16_bit_mt19937_key;
+pub use crack::recover_mt19937_key_from_time;
diff --git a/tests/lib.rs b/tests/lib.rs
index d38e3e3..3961b84 100644
--- a/tests/lib.rs
+++ b/tests/lib.rs
@@ -512,3 +512,12 @@ fn problem_24 () {
     ).unwrap();
     assert_eq!(got, key);
 }
+
+#[test]
+fn problem_24_part_2 () {
+    let seed = time::now().to_timespec().sec as u32;
+    let mut mt = matasano::MersenneTwister::from_seed(seed);
+    let token: Vec<u8> = mt.gen_iter().take(16).collect();
+    let got = matasano::recover_mt19937_key_from_time(&token[..]).unwrap();
+    assert_eq!(got, seed);
+}