> 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/51.-hashpump.md).

# 51. HashPump

## Overview

HashPump is a tool for performing **hash length extension attacks** against MD5, SHA-1, SHA-256, and SHA-512.

**GitHub:** <https://github.com/bwall/HashPump>

## Installation

```bash
# From source
git clone https://github.com/bwall/HashPump
cd HashPump
make
sudo make install

# Python binding
pip install hashpumpy
```

## When to Use

Use when a server computes: `H(secret || user_data)` and returns the hash.

You can forge: `H(secret || user_data || padding || extra_data)` without knowing the secret.

## CLI Usage

```bash
hashpump
```

Interactive prompts:

```
Input Signature: <original hash>
Input Data: <original message>
Input Key Length: <guessed key length>
Input Data to Add: <your appended data>
```

Output:

```
New Signature: <forged hash>
New String: <URL-encoded new message>
```

## Python (hashpumpy)

```python
import hashpumpy

original_hash = "d79e1c308aa5bbcdeea8ed63df412da9"
original_data = "count=10&lat=37.351&user_id=1&long=-119.827&waffle=eggo"
data_to_add   = "&waffle=liege"
key_length    = 14  # guess or brute-force

new_hash, new_data = hashpumpy.hashpump(
    original_hash,
    original_data,
    data_to_add,
    key_length
)

print("New hash:", new_hash)
print("New data:", new_data)
```

## Brute-Force Key Length

If the key length is unknown, iterate:

```python
for key_len in range(1, 50):
    new_hash, new_data = hashpumpy.hashpump(
        original_hash, original_data, data_to_add, key_len
    )
    # Submit to server and check if accepted
```

## Padding Structure

The padding appended between original data and your addition:

```
\x80 \x00 \x00 ... \x00 <64-bit length>
```

This padding is part of the Merkle–Damgård construction.

## Supported Hash Functions

| Hash    | Hashpump Mode    |
| ------- | ---------------- |
| MD5     | ✅                |
| SHA-1   | ✅                |
| SHA-256 | ✅                |
| SHA-512 | ✅                |
| SHA-3   | ❌ (sponge)       |
| HMAC    | ❌ (double-keyed) |


---

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