Ethereum: Format of mkey field in encrypted wallet.dat file

Ethereum Wallet.dat File Format: Key Field Verification

When scanning large files for encrypted wallet.dat files, it is important to understand the format of the key field in these files. This is crucial for recovering private keys from victims’ wallets.

In this article, we will take a look at the Ethereum wallet.dat file format and focus specifically on the structure of the mkey field.

Overview of the Ethereum Wallet.dat File Format

The Ethereum wallet.dat file format is a binary format used to store encrypted wallet data. The file consists of three main sections:

• Header: This section contains metadata about the file, including its name and version.

• Index Block: This section is used for indexing purposes, allowing for efficient searching for specific blocks in the blockchain.

• Wallet Data: This section stores encrypted wallet data.

The mkey Field

Within the mkey field, we will focus on the structure and content of this field specifically.

Block Header Format

Before we dive into the mkey field, let’s look at the format of the block header:

Header:
Version (4 bytes)
Flags (4 bytes)
Block Number (8 bytes)

The block number is stored as a 64-bit unsigned integer in byte order.

Index Block Format

In the index block section, we find the following fields:

• BlockHash: The hash of the previous block.

• TransactionCount: The number of transactions included in this block.

• IndexBlockHash: The hash of the index block header (not shown here).

The mkey field is located in the block section of the index. It is a 256-bit word, which is a 32-byte unsigned integer.

mkey field format

The mkey field consists of two fields:

• Version: A single byte that indicates the type of data stored in this field.

• Hash: The hash value of the primary key (in bytes).

Here is an example of what the mkey field might look like:

Index block 1:
mkey: 0x12345678 0x90123456 // Version, hash

To reconstruct the original key, we can extract theVersionandHashfields from eachmkeyfield. Since there are multiplemkeyfields in a single index block, we need to combine them.

Assuming two consecutive blocks with identicalmkeystructure, we can represent the reconstructed key as follows:

Reconstructed key:
Version: 0x12345678
Hash: 0x90123456 0x87654321

In conclusion, understanding the format of the mkeyfield in Ethereum wallet.dat files is crucial for recovering private keys from victims' wallets. By analyzing the block header and the index block sections, we can recover the original key using the extractedVersionandHashfields.

When writing a C++ application to scan large files for encrypted wallet.dat files, be sure to carefully analyze eachmkey` field in individual blocks to accurately recover the private keys.