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# Rev - Random security
## Description
## Solution
Interaction with server
In this challenge, the server gives us a random number and if we give back a wrong number, it will print **"WRONG DOUBLE!!!!!"**. Also, in the challenge description, the word **Java** is highlighted which suggest that this challenge has something to do with Java randomization.
A quick google search reveals that Java's random is just a linear congruential generator which can be easily cracked. Rather than reinventing the wheel, I will use the code from this Github page:
The modified Java code:
```java
import java.util.Random;
public class ReplicatedRandomTest {
public static void main(String args[]) {
Random r = new Random();
ReplicatedRandom rr = new ReplicatedRandom();
rr.replicateState(Double.parseDouble("0.9326890248362221"));
for (int j = 0; j < 10; j++)
System.out.println(rr.nextDouble());
System.out.println();
}
}
```
The code will predict the next 10 doubles but we will only need the first one.
Predicted number
Flag: `bucket{RaNd0m_nUmb3r5_53cur3_d24d8c961}`
---
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