sha256

Security Concepts

Definition

SHA-256 stands for **Secure Hash Algorithm 256-bit**. It’s a **cryptographic hash function** — basically, a digital blender that takes any input (a file, password, message) and mixes it into a **fixed-length string** of 256 bits (64 hexadecimal characters).

Once something goes into the blender, you can’t get it back out — it’s a **one-way function**.

### 📦 Key Properties

| Property                | Meaning                                                                               |
| ----------------------- | ------------------------------------------------------------------------------------- |
| **Fixed length**        | No matter if you hash “Hi” or an entire book, the output is always 256 bits long.     |
| **Deterministic**       | The same input always gives the same hash.                                            |
| **Avalanche effect**    | Even a tiny change in input (like changing one letter) completely changes the output. |
| **One-way**             | You can’t reverse the hash to get the original input.                                 |
| **Collision-resistant** | It’s extremely hard to find two different inputs that produce the same hash.          |

### 🖼️ Visual Metaphor

```
[ Input: "Hello" ] → SHA-256 → 2cf24dba5f... (64 hex characters)
[ Input: "hello" ] → SHA-256 → 5d41402abc... (completely different!)
```

Or think of SHA-256 as a **super-secure fingerprinting machine**:

* Same object → same fingerprint
* Slight scratch → completely different fingerprint
* Can’t rebuild the original from the fingerprint

### 🔐 Why We Use It in Cybersecurity

* **Password storage** (with added salt for extra security)
* **Integrity checks** for files (to ensure they weren’t tampered with)
* **Blockchain transactions** (Bitcoin uses SHA-256 heavily)

📌 **Pro tip:**
SHA-256 is great for integrity, but don’t use it for password storage *alone*. Add a salt and use a slow hashing algorithm (like bcrypt) to make it harder for attackers.

Got it — let’s put SHA-256 in the **cyber detective** context so it feels right at home in a KC7 investigation.

## 🕵️ How We Might Use SHA-256 in an Investigation

When you’re investigating a cyber incident, SHA-256 hashes can act like **digital DNA** for files.

Here’s how:

**Identifying Malicious Files**

* If you find a suspicious file on a compromised system, you can generate its SHA-256 hash.
   * That hash can be searched in malware databases (like [VirusTotal](https://www.virustotal.com)) to see if it’s a known malicious sample.
   
**Verifying Integrity**

* Suppose an attacker replaced a system file with a trojanized version. Comparing the SHA-256 of the suspect file to a known-good copy tells you if it’s been altered.
   
**Correlating Across Systems**

* You might see the same SHA-256 hash appear in logs from different machines. That’s a strong clue the same malicious file spread across the network.
   
**Tracking Data Leaks**

* If a stolen document is floating around online, you can hash the original and check for matches to see if it’s really yours.

**Timeline Building**

* A single SHA-256 found in multiple places at different times helps connect dots — e.g., *this phishing email attachment* was later *executed on these endpoints*.

### 🖼️ Diagram: “SHA-256 in the Cyber Detective Toolkit”

```
[ Suspicious File ] --hash--> [ SHA-256 Fingerprint ]
       |                              |
       v                              v
   Malware DB search           Compare with known good
       |                              |
   Known threat?            Changed? Yes → Compromised
```

## 📚 Additional Reading

* **NIST FIPS PUB 180-4** – [Secure Hash Standard](https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.180-4.pdf) (official spec for SHA-256 and friends)
* **VirusTotal** – [https://www.virustotal.com](https://www.virustotal.com) (search a hash to check for known malware)
* **Hashing 101** (Cloudflare blog) – [https://www.cloudflare.com/learning/cryptography/what-is-hashing/](https://www.cloudflare.com/learning/cryptography/what-is-hashing/)
* **Blockchain and SHA-256** (Investopedia) – [https://www.investopedia.com/terms/s/sha-256-algorithm.asp](https://www.investopedia.com/terms/s/sha-256-algorithm.asp)

sha256

Definition

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