Classic Tool 2.3.1 - Mifare

To understand why MCT 2.3.1 is so powerful, you must understand the MIFARE Classic’s fatal flaw: CRYPTO-1 encryption.

The MIFARE Classic uses a proprietary stream cipher called Crypto-1. For years, it was considered secure. However, in 2008, researchers reverse-engineered the algorithm. By 2019 (when the core logic of MCT 2.3.1 was maturing), tools could break a 48-bit key in under 2 minutes using a standard smartphone.

MCT 2.3.1 exploits three specific vulnerabilities:

The app doesn't just "crack" the card; it listens to the conversation between your phone's NFC chip and the card, deduces the secrets, and allows you to rewrite sectors.

Mifare Classic Tool (MCT) is an Android application designed to read, write, and analyze MIFARE Classic RFID tags. It is intended for security researchers, system administrators, and electronics enthusiasts to audit access control systems or manage RFID hardware. mifare classic tool 2.3.1

Version 2.3.1 is a maintenance release focused on stability improvements, UI bug fixes, and compatibility updates for modern Android versions.

Since brute-forcing 48-bit keys is computationally infeasible on mobile hardware, MCT employs a dictionary attack.

For the locked sectors:

You might ask: Why focus on 2.3.1 when the current version is 4.x? To understand why MCT 2

This is critical for long-time users. The developer, ikarus23, made significant architectural changes after version 3.0. While newer versions (4.x) support NFC tags and improved UI, they removed some "aggressive" attacks to comply with Google Play Store policies.

MIFARE Classic Tool 2.3.1 is the last version that:

For this reason, professionals keep an old Android phone running Android 7 or 8 with MCT 2.3.1 specifically installed.

As of 2025, most high-security systems have moved away from MIFARE Classic. However, legacy systems are pervasive: The app doesn't just "crack" the card; it

Because of this, MIFARE Classic Tool 2.3.1 remains the most downloaded RFID tool on F-Droid. It is textbook software—imperfect, dangerous in the wrong hands, but absolutely brilliant for learning how hardware security fails.

An Analysis of Low-Frequency RFID Security Auditing on Android

Date: October 26, 2023 Subject: Security Analysis, Feature Set, and Operational Methodology Target Audience: Security Researchers, System Administrators, Penetration Testers