> For the complete documentation index, see [llms.txt](https://alham-rizvi.gitbook.io/alhamrizvi/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://alham-rizvi.gitbook.io/alhamrizvi/cryptography/hashing/13.-ripemd-160.md).

# 13. Ripemd-160

### 1. What RIPEMD-160 Is

RIPEMD-160 is a **cryptographic hash function** designed as an alternative to SHA-1.

* Output size: **160 bits**
* Displayed as: **40 hexadecimal characters**

Example:

```
Input  → hello  
RIPEMD-160 → 108f07b8382412612c048d07d13f814118445acd
```

***

### 2. Why It Exists

It was created to provide:

* a non-US alternative to SHA-1
* stronger design than older hashes like MD5

It improves security by using a more complex internal structure.

***

### 3. Core Properties

* One-way (cannot reverse hash → input)
* Deterministic
* Fixed output size (40 hex chars)
* Strong avalanche effect
* No practical full collision attacks known

***

### 4. How It Works (Simple Understanding)

RIPEMD-160 processes data in a unique way:

#### Key idea:

It uses **two parallel computation paths**

```
Left branch  → processes input
Right branch → processes input differently
```

Both branches:

* run multiple rounds
* use different constants and operations
* are merged at the end

***

#### High-level steps:

1. Pad input
2. Split into 512-bit blocks
3. Process through 80 rounds
4. Combine parallel results
5. Output 160-bit hash

***

### 5. Where It Is Used (Important)

#### Blockchain (especially Bitcoin)

Bitcoin uses:

```
RIPEMD160(SHA256(public_key))
```

This is called:

### 👉 Hash160

***

#### Why both SHA-256 and RIPEMD-160?

* SHA-256 → strong hashing
* RIPEMD-160 → shorter output (better for addresses)

This combination improves:

* usability
* compactness

***

### 6. Tools and Commands

#### Linux

```bash
echo -n "hello" | openssl dgst -ripemd160
```

***

#### Python

```python
import hashlib

h = hashlib.new('ripemd160')
h.update(b'hello')
print(h.hexdigest())
```

***

### 7. Security Status

RIPEMD-160 is:

* Still considered secure
* No practical full collisions known
* Less studied than SHA-2

***

#### Limitations

* Smaller output than modern hashes
* Older design
* Not widely used outside blockchain

***

### 8. Comparison

| Feature  | RIPEMD-160 | SHA-256     |
| -------- | ---------- | ----------- |
| Output   | 160-bit    | 256-bit     |
| Security | Good       | Stronger    |
| Usage    | Blockchain | Everywhere  |
| Design   | Dual-path  | Single-path |

***

### 9. CTF Mindset

When you see RIPEMD-160:

* Do not try to reverse it directly
* Look for:
  * small input space
  * known values
  * chained hashes (e.g., SHA256 → RIPEMD160)

***

### 10. Key Insight

RIPEMD-160 is not popular because it’s the best.

It is used mainly because:

> systems like Bitcoin were built around it and kept it for compatibility

***

### 11. Final Summary

RIPEMD-160 is:

* A 160-bit cryptographic hash
* Designed as an alternative to SHA-1
* Still used in blockchain (Hash160)
* Secure but not modern standard

***

#### Core Idea

RIPEMD-160 shows how:

> older but secure designs can remain important due to real-world adoption, especially in blockchain systems.


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://alham-rizvi.gitbook.io/alhamrizvi/cryptography/hashing/13.-ripemd-160.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.