# RIPEMD-160 Overview

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#### Why Learn About RIPEMD-160?

The other important hash function used in **BSV** is **RIPEMD-160**.

* You don’t need to know its inner workings to understand Bitcoin.
* But seeing its **design philosophy and history** helps highlight why it’s trusted and still relevant.

***

#### A Brief History of RIPE (Race Integrity Primitives Evaluation)

In the **1990s**, the **European Union** established the **RIPE consortium** to develop better **integrity primitives** (cryptographic tools to ensure data integrity).

At the time:

* The most popular hash functions were **MD4** and **MD5**, created by Ron Rivest.
* RIPE evaluated these and proposed **RIPEMD**, a stronger version of MD4.

👉 **RIPEMD** essentially ran **two parallel versions of MD4** with improvements to **bit shifts** and **word ordering**.

Shortly after, **SHA-1** was published by NIST as an MD5-based improvement.

***

#### RIPEMD-160

In **1995**, cryptographer **Hans Dobbertin** found **collisions** in the original RIPEMD.

* In response, **Dobbertin et al. (1996)** proposed **RIPEMD-160** and **RIPEMD-128**.
* Both are still considered **secure hash functions today**.

Key changes in **RIPEMD-160**:

* **160-bit output** (longer digest for stronger security).
* **Five rounds of compression** (instead of three).
* Carefully chosen **bit shifts (5–15 bits)**.
* Each message block rotated by **different amounts**.
* Shifts and constants chosen to avoid exploitable patterns.

Performance trade-offs:

* \~15% slower than **SHA-1**.
* Half as fast as the original **RIPEMD**.
* Four times slower than **MD4**.
* On modern processors, this **performance hit is negligible**.

👉 **Design philosophy:** Make the **minimum necessary changes** to strengthen RIPEMD while preserving confidence from MD4, MD5, and RIPEMD research.

***

#### Use Cases

* In **Bitcoin (and therefore, BSV)**, RIPEMD-160 is combined with SHA-256 to produce **HASH-160** (used in address creation).
* Outside Bitcoin, it is notably used in **PGP (Pretty Good Privacy)** for **email encryption**.

***

✅ **Summary:** RIPEMD-160 is a **secure, reliable, and efficient hash function** that balances **proven design principles** with **increased security**, making it suitable for long-term cryptographic use.


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