2018: Bitfi - You Wouldn't Steal My Cloins by Andrew Tierney (@cybergibbons)

# Overview Andrew Tierney discusses comprehensive security vulnerabilities discovered in the Bitfi hardware wallet, which was marketed as "unhackable" by John McAfee. The device claimed to store private keys only in the user's head via a brain wallet model, but security research revealed fundamental design and implementation flaws across multiple attack vectors.

# Key Topics Bitfi is a WiFi-connected hardware wallet based on a heavily modified MediaTek Android phone. Unlike traditional hardware wallets (Ledger, Trezor) that securely store keys, Bitfi requires users to type their private key every time, supposedly preventing theft if the device is compromised. The team discovered this design is fundamentally flawed.

# Technical Details **Hardware Contradictions:** Despite marketing claims of "no memory to hack," the device contains both eMMC flash storage and LPDDR3 RAM. Initial units lacked FCC certification despite containing RF components. Serial numbers on boxes didn't match device internals, suggesting supply chain tampering.

**Vulnerability Categories:** 1. **Touch Input:** Unencrypted I2C capacitive touch panel communication allows attackers to read finger coordinates using logic analyzers 2. **Firmware Access:** SP Flash Tool enables firmware dumping; secure boot is disabled 3. **Memory Extraction:** Private keys remain in RAM long after use (one device retained keys for two weeks); team recovered passphrases from memory dumps 4. **Viewing Angle:** Display visibility claims were false; team recovered a passphrase from an enhanced image posted by a Bitfi defender 5. **Cold Boot Attack:** Specialized tools allowed complete memory extraction in under 2 minutes after device restart, recovering keys and passphrases before they degrade 6. **Runtime Hooking:** Using Frida to intercept Java layer secrets; arbitrary transaction messages could be injected after routing the device 7. **WiFi Credential Recovery:** Recovered CEO's WiFi SSID and PSK from bounty devices via cold boot attacks

**Root Causes:** No secure boot implementation, brain wallet model fundamentally incompatible with secure key handling, lack of memory scrubbing, unencrypted internal communications, and core reliance on an unsuitable Android phone platform.

# Bounty Program Failures Bitfi offered $400,000 (later $10,000) bounties with restrictive rules requiring attacks on their supplied wallets. The research team successfully demonstrated multiple vulnerabilities meeting all bounty criteria. Bitfi discontinued the bounty program immediately after vulnerabilities were disclosed and refused to pay out.

# Social and Marketing Issues John McAfee claimed to have invented cybersecurity and heavily promoted Bitfi despite clear vulnerabilities. Marketing claims included "unhackable," "no RAM," "not a phone," and "narrow viewing angle prevents shoulder surfing"—all proven false. McAfee made threatening statements when challenged, invited the researcher to his house, and posted edited fake news articles attacking them.

# Takeaways The research demonstrates that hardware wallet security depends entirely on proper implementation. "Unhackable" claims are red flags. Even conceptually sound designs fail with poor engineering (no secure boot, inadequate memory handling). Supply chain security remains a critical unsolved problem. The brain wallet model is fundamentally problematic for daily use. Ultimate trust in hardware wallets rests on manufacturer integrity, making Bitfi's marketing deception particularly damaging. Cold boot and data remanence attacks remain viable threats that are difficult to fix remotely.