The following step by step tutorial on how to crack a wallet.dat file provided insights into AES-256-CBC vulnerability to Padding Oracle Attack. This attack takes the lead over the regular Brute Force Attacks as it is far time and resource efficient as compared to the latter.
Table of Contents
What is a Wallet.dat File?
Before going into details on how to crack a wallet.dat file, let’s understand some basics. A wallet.dat file is a data file used by Bitcoin and other cryptocurrency wallets to store sensitive information. These include the private keys and other data required to access and manage cryptocurrency holdings. It is the key component of a traditional Bitcoin wallet and is typically used by the Bitcoin Core software.
Here are some important aspects of the wallet.dat file:
Private Keys: The wallet.dat file contains private keys. These keys are essential for signing transactions and proving ownership of the cryptocurrency stored in the wallet. These private keys allow you to send Bitcoin (or other cryptocurrencies) from the wallet.
Public Keys: Along with private keys, the wallet.dat file also contains public keys. These keys generate the addresses that others can send cryptocurrency to, but they cannot solely access the wallet’s funds.
Transaction Data: It may store the transaction history associated with the wallet, including received and sent payments.
Encrypted Wallets: For security, Bitcoin Core encrypts the wallet.dat file with a password. It ensures that even if someone gains access to the file, they cannot access the funds without the correct password.
Backup: The wallet.dat file is crucial for backup purposes. If the wallet’s software or device is lost or damaged, the wallet.dat file can be restored to recover the wallet’s contents.
Because of the sensitive nature of this file, it’s very important to keep the wallet.dat file secure. If someone else gains access to it (especially the private keys), they could steal the cryptocurrency stored in the wallet.
A Word About Lost or Abandoned Wallets
There are numerous wallet.dat files circulating across the internet. They are often found in online forums, file-sharing networks, or in abandoned or lost repositories. These files contain the potential to hold cryptocurrency. But without knowledge of the associated private keys or passwords, they remain inaccessible. The lack of information about their original owners or passwords adds to the mystery and intrigue. Thus many people believe these files might contain forgotten or lost fortunes. Several number of people have been trying to crack the wallet.dat files for years but a very few succeeded in this pursuit. Unless the correct decryption key is found, these wallet.dat files are essentially worthless, as accessing the funds inside is impossible without the necessary credentials. The phenomenon has sparked both curiosity and debate about the fate of digital assets in cases of lost access.
There are several tools available today which are capable of cracking a wallet.dat file. Some of them include Hashcat, John The Ripper, Pywallet, Btcrecoverer etc. All these tools implement the mechanism of Bruteforce to recover the wallet’s passwords. That means that they try millions and trillions of combinations to find the correct password. The bruteforce method is quite exhausting and needs expensive and powerful hardware resources. In this tutorial, I am going to demonstrate a new method to crack bitcoin core wallet.dat password which is a bit complex than brute force but it is time and resources friendly. It is called ‘Padding Oracle Attack’
What is Padding Oracle Attack?
In cryptography, a padding oracle attack is an attack which tries to validate the padding. It, then, exploits the paddings to deciphers the ciphertext (the password in case of a wallet.dat file). As per Wikipedia:
“In cryptography, a padding oracle attack is an attack which uses the padding validation of a cryptographic message to decrypt the ciphertext. In cryptography, variable-length plaintext messages often have to be padded (expanded) to be compatible with the underlying cryptographic primitive. The attack relies on having a “padding oracle” which freely responds to queries about whether a message is correctly padded or not. Padding oracle attacks mostly work with CBC mode decryption used within block ciphers. Padding modes for asymmetric algorithms such as OAEP may also be vulnerable to padding oracle attacks.”
In symmetric cryptography, the OP attack can be performed on the AES-256-CBC mode of encryption (as Bitcoin Core). In this attack the “oracle” (the wallet.dat file) leaks data about whether the padding of an encrypted message is correct or not. Such data can allow attackers to decrypt messages through the oracle using the oracle’s key, without knowing the encryption key.
How I Discovered the Padding Oracle Attack?
During my PhD research in 2023, focused on Zero-Knowledge Proofs (ZKPs) and Privacy, I discovered an intriguing connection between classical cryptographic vulnerabilities and the emerging privacy-preserving technologies. While exploring the integration of ZKPs with other cryptographic primitives to enhance privacy in decentralized applications, I stumbled upon the Padding Oracle Attack. This attack, which exploits the way some encryption schemes handle padding in block ciphers, revealed a critical gap in the security of systems that rely on traditional encryption methods for protecting sensitive information. The attack’s ability to decrypt ciphertexts by manipulating padding errors exposed vulnerabilities in some cryptographic implementations, emphasizing the need for more robust error-handling mechanisms in privacy-focused protocols. This discovery highlighted the intersection of classical cryptographic weaknesses with modern privacy techniques, deepening my understanding of both the theoretical and practical challenges in designing secure and privacy-preserving cryptographic protocols.
Usually the Padding Oracle Attack is typically considered a server-side vulnerability. But I decided to explore its implications on local files with AES-256-CBC encryption in my research. So I intended to apply it on how to crack a wallet.dat file. This shift in focus allowed me to examine how this well-known attack could be applied to locally stored, encrypted data especially wallet.dat file—often assumed to be more secure because it doesn’t involve network communication.
I found that even in offline environments, where the attacker has direct access to the encrypted files, the lack of proper error handling and feedback mechanisms for padding validation can still present a significant security risk. By manipulating ciphertexts and observing the system’s response to padding errors, an attacker can recover plaintext information and easily recover wallet.dat password. This investigation provided valuable insights into how local encryption systems, if not carefully implemented, could be vulnerable to the same kinds of padding oracle attacks that are commonly associated with web servers and network protocols.
What is This Tutorial About?
This tutorial is the culmination of seven months of rigorous research on using the Padding Oracle Attack to crack a wallet.dat file. The focus of this tutorial is purely educational and for research purposes only. It aims to explore and demonstrate the vulnerabilities inherent in certain cryptographic implementations. Specifically, I investigated how AES-256-CBC encryption, which is implemented in Bitcoin Core to secure wallet.dat files, could be susceptible to padding oracle attacks in offline environments.
Python Not C... Surprised?
Many programmers consider C a top priority for penetration testing and cybersecurity analysis. However, I chose to implement the Padding Oracle Attack using Python for a few key reasons. First and foremost, I am much more fluent in Python. It allowed me to rapidly prototype and iterate on the attack code with greater ease and flexibility. Python’s extensive libraries, such as PyCryptodome for cryptography and pywallet for wallet interaction, provided me with powerful tools to implement the attack in a straightforward manner.
Additionally, my research focused on offline attacks against locally stored file. Hence the computational efficiency of C was not a critical factor. The complexity of a low-level implementation wasn’t necessary, as the attack was being executed on a single wallet.dat file, not in a real-time network environment or high-performance setting. The primary goal was to demonstrate the conceptual attack and explore its practical impact on AES-256-CBC encrypted data, rather than to optimize the code for speed or scalability.
Step by Step Guide on How to Crack a Wallet.dat File
I coded this program using Python. Therefore, there are some specific requirements before trying this program to crack a wallet.dat file password. As far as the hardware requirements are concerned, there is no need of an intensive system, as you can run this program on a simple computer as well. However, the better hardware you have, the sooner it is going to detect the paddings and crack the password. I ran this code both on a CPU based computer and a GPU Powered one. It took me around 47 minutes on CPU and 13 minutes on a GPU based system.
Other requirements entail some mandatory pre-requisites which are necessary to set up the environment to run the program. These requirements consist of a compatible Python version and some Python packages required to perform padding detection, blocks sorting and finally decipher the password.
Step 1: Fulfill The Requirements
You will need to install Python on your system to set up the environment for running this program. The version needed to run the padding oracle attack is Python 3.x. I used Python v3.9 for testing the program. You can download and install Python from the following link:
A step by step tutorial to install Python on both Windows and MacOS is as follows:
How to Install Python on Windows and Mac
After you have installed Python on your system, it is time to install the required Python packages. You can find the list of these libraries in the file ‘Requirements.txt’ when you download the program code. Below is the list of all the Python libraries that you will need to crack a wallet.dat file password.
PyCryptodome
PyOpenSSL
Pandas
Sys
Math
bitcoinlib
json
hashlib
base58
You can install the above mentioned libraries in 2 ways: Using the file ‘Requirements.txt’ or using pip and libraries names. For installing using the requirements file, open the console in the folder where the requirements file is located and write write the following command into your console and press Enter
pip install -r Requirements.txt
To install the libraries using pip and libraries names, use the following command in your console and press enter:
pip install PyCryptodome,PyOpenSSL,Pandas,Sys,Math,bitcoinlib,json,hashlib,base58
Step 2: Download Pywallet for Extracing Data from the Wallet.dat File
After installing Python 3.x and required libraries, it is time to download Pywallet. Pywallet is an open-source Python tool designed for interacting with Bitcoin wallet files, specifically the wallet.dat files used by Bitcoin Core. This tool plays a crucial role in cracking a wallet.dat file. Crypto Analysts commonly use this tool for tasks such as recovering or extracting private keys, master key and addresses from Bitcoin wallet files. I have included the Pywallet tool along with the Padding Oracle program. Once you download the files from the link given at the bottom of the article, you will find the Pywallet tool in the folder named as Pywallet.py. Alternatively, you can also download Pywallet from the following link:
Step 3: Extract Mkey, Iterations and Salt from the Wallet File
Place your wallet.dat file in the same folder where Pywallet.py is located. You need to extract the Master key, number of iterations and Salt of the wallet using Pywallet. To extract this data, open your terminal in the same folder, enter the following command in your terminal and press Enter. After a few seconds, this command will generate a new file in the folder as “wallet.txt”
python pywallet.py --dumpwallet --datadir=. > wallet.txt
Now open the ‘wallet.txt’ file and you will find mkey, iterations and salt at the bottom of it. Copy these values and save them in another file for future use.
Step 4: How to Crack a Wallet.dat File with Padding Oracle Script
After you have gathered the important data from the wallet.dat file i.e. mkey, number of iterations and salt, it’s time to recover the wallet.dat password file using the padding oracle program. This program also comes in the same folder named as ‘OPAttack.py’. Please note that this program detects your hardware automatically, so it uses system resources as available without affecting the overall speed of the system. For example, if your CPU has 32 threads, the program will utilize half of the threads so that the other ongoing processes on the system do not hang or suspend. As you have the required data, let’s proceed further on how to crack the wallet.dat file. Now keep the mkey, iterations and salt saved in a text file, enter the following command in your terminal and press ENTER:
python OPAttack.py --mkey MKEY --iterations ITERATIONS --salt SALT
Replace the words written in capital letters, with your corresponding values. For example
python OPAttack.py --mkey de5fa48d609c1d4a1bc77b59c0ea57499c2c5bcf52d129f025a647d8ba498ce5e0a02cd81ae9d55d6c2dc391dfd596fa --iterations 268678 --salt fff06e9d9c297c90
As your press enter, the Padding Oracle script will start working on the data to detect the paddings in the blocks. If it finds a padding in a block, it will try to test it against several iterations until it finds the correct one. These detected paddings will thus help to decipher the passphrase. After the program has cracked the wallet.dat password, it will store it in a file named ‘Passphrase.txt’ automatically. Just open the file and look for the password in the last 10 lines of the file as depicted in the video.
How to Download the Padding Oracle Attack Program
If you have lost password to your wallet, padding oracle attack is handy to recover wallet.dat password. As mentioned earlier, it is far efficient than the traditional bruteforce attack when it comes to time and resources. To download the program, just click on the link given below, and you will be redirected to the download page. Please note that the folder contains several files. The only two files which you are going to use to crack wallet.dat file, are ‘Pywallet.py’ and OPAttack.py. At the end of this page, a live demo is also given which you can follow to recover the wallet.dat password. For any queries, you can reach out to me via email or Telegram listed below.
Contact
If you have any technical queries related to the Padding Oracle attack program, you can reach out to me via email or Telegram given below.
Telegram
@jacobmrx
jacobmi.791@gmail.com
Live Demo on Padding Oracle Attack to Crack a Wallet.dat File
