From 82fde31b637e72d381857e3e2cb669298073edd1 Mon Sep 17 00:00:00 2001
From: Jesse Luehrs <doy@tozt.net>
Date: Mon, 6 Apr 2015 01:26:20 -0400
Subject: real problem 22

---
 Cargo.lock   | 10 ++++++++++
 Cargo.toml   |  1 +
 src/crack.rs | 15 ++++++++++++++-
 src/lib.rs   |  2 ++
 tests/lib.rs | 12 ++++++++++++
 5 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/Cargo.lock b/Cargo.lock
index a8904f1..c4ca95f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -5,6 +5,7 @@ dependencies = [
  "openssl 0.5.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-serialize 0.3.12 (registry+https://github.com/rust-lang/crates.io-index)",
+ "time 0.1.24 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -89,3 +90,12 @@ name = "rustc-serialize"
 version = "0.3.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "time"
+version = "0.1.24"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "gcc 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
diff --git a/Cargo.toml b/Cargo.toml
index 544ff50..bc2f6cf 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -8,3 +8,4 @@ authors = ["Jesse Luehrs <doy@tozt.net>"]
 rustc-serialize = "0.3"
 openssl = "0.5"
 rand = "0.3"
+time = "0.1"
diff --git a/src/crack.rs b/src/crack.rs
index b351249..396eb6b 100644
--- a/src/crack.rs
+++ b/src/crack.rs
@@ -1,7 +1,7 @@
 use std::ascii::AsciiExt;
 use std::borrow::ToOwned;
 use std::collections::{HashMap, HashSet};
-use rand::SeedableRng;
+use rand::{Rng, SeedableRng};
 
 use data::ENGLISH_FREQUENCIES;
 use primitives::{fixed_xor, unpad_pkcs7, hamming, repeating_key_xor};
@@ -357,6 +357,19 @@ pub fn crack_fixed_nonce_ctr_statistically (input: Vec<Vec<u8>>) -> Vec<Vec<u8>>
     return plaintext_lines;
 }
 
+pub fn recover_mersenne_twister_seed_from_time (output: u32) -> Option<u32> {
+    let now = ::time::now().to_timespec().sec as u32;
+    for i in -10000..10000i32 {
+        let seed = (now as i32).wrapping_add(i) as u32;
+        let mut mt = MersenneTwister::from_seed(seed);
+        let test_output: u32 = mt.gen();
+        if test_output == output {
+            return Some(seed);
+        }
+    }
+    return None;
+}
+
 pub fn clone_mersenne_twister_from_output (outputs: &[u32]) -> MersenneTwister {
     fn untemper (val: u32) -> u32 {
         fn unxorshift<F> (f: F, mut y: u32, n: usize, mask: u32) -> u32 where F: Fn(u32, usize) -> u32 {
diff --git a/src/lib.rs b/src/lib.rs
index bbaf93f..21bac75 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,6 +1,7 @@
 extern crate rustc_serialize as serialize;
 extern crate openssl;
 extern crate rand;
+extern crate time;
 
 mod aes;
 mod base64;
@@ -36,5 +37,6 @@ pub use crack::find_single_byte_xor_encrypted_string;
 pub use crack::crack_single_byte_xor;
 pub use crack::crack_repeating_key_xor;
 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;
diff --git a/tests/lib.rs b/tests/lib.rs
index da8516d..d38e3e3 100644
--- a/tests/lib.rs
+++ b/tests/lib.rs
@@ -1,6 +1,7 @@
 extern crate matasano;
 extern crate rustc_serialize as serialize;
 extern crate rand;
+extern crate time;
 
 use std::ascii::AsciiExt;
 use std::borrow::ToOwned;
@@ -474,6 +475,17 @@ fn problem_21 () {
     assert_eq!(&got[..], &expected[..]);
 }
 
+#[test]
+fn problem_22 () {
+    // std::thread::sleep_ms(rand::thread_rng().gen_range(40, 1000) * 1000);
+    let seed = time::now().to_timespec().sec as u32;
+    let mut mt = matasano::MersenneTwister::from_seed(seed);
+    // std::thread::sleep_ms(rand::thread_rng().gen_range(40, 1000) * 1000);
+    let output: u32 = mt.gen();
+    let got = matasano::recover_mersenne_twister_seed_from_time(output).unwrap();
+    assert_eq!(got, seed);
+}
+
 #[test]
 fn problem_23 () {
     let mut mt: matasano::MersenneTwister = rand::thread_rng().gen();
-- 
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