HASHING

## HASHING
hashing isn’t strictly necessary, but it's much better practice — especially in research or secure implementations. WITHOUT HASHING THE IV USING sha256, IMAGE IS STILL RESEMBLING THE ORIGINAL IMAGE LITTLE BIT IF WRONG IV USED.

#### 🔒 Why Use `sha256(iv).digest()` with key/IV Instead of key/IV Directly?

Using a cryptographic hash of the IV (like `sha256(iv).digest()`) provides several **important advantages**, especially in encryption schemes that depend on **chaotic maps** or **keystreams**.

---

##### 🔑 1. **Better Diffusion (Small Change → Big Difference) MAIN THING**

Hash functions like SHA-256 exhibit the **avalanche effect**:

> A **small change in the IV** results in a **completely different hash output**.

This greatly increases the **unpredictability** of the chaotic keystream — which is ideal for image encryption, where any repeating or patterned output is a weakness.

---

#### 🔐 2. **Longer, Uniform Output**

A 16-byte IV becomes a **32-byte SHA-256 hash**, which:

- Adds **more entropy** to the system.
- Ensures a **uniform distribution of bytes**, important when generating seeds for logistic maps.
- Allows precise mapping to the interval (0, 1), where most chaotic maps operate, while maintaining high resolution.

---

#### 🛡️ 3. **Hides Structure of the IV**

If the IV was weak or had visible structure (e.g., `0000000000000001`), then:

- Direct use might lead to **predictable seeds** and hence **predictable chaotic sequences**.
- Security would be significantly weakened.

By hashing the IV, the resulting seed is **pseudo-random** and **uniformly distributed**, hiding any weaknesses in the original IV.

---

### ✅ Summary Table

| Using IV Directly         | Using `sha256(iv).digest()`         |
|---------------------------|-------------------------------------|
| Less entropy              | High entropy                        |
| Poor diffusion            | Strong diffusion                    |
| May leak IV structure     | Hides original IV completely        |
| Less secure as seed       | Cryptographically stronger seed     |