BitLocker<\/a> keys without PIN protection, where attackers could exploit stolen laptops, researchers now delve into PIN-secured setups, targeting insider threats seeking SYSTEM-level access.<\/p>\n This technique involves intercepting TPM communications via SPI bus analysis, revealing how even PIN-hardened BitLocker can yield to physical probing with known credentials. <\/p>\n While no true bypass occurs, the method unlocks drives efficiently, highlighting persistent hardware vulnerabilities in enterprise encryption.<\/p>\n Unlike TPM-only configurations that auto-unseal keys during boot, PIN-protected BitLocker layers<\/a> additional safeguards.<\/p>\n The Full Volume Encryption Key (FVEK) remains on the disk, encrypted by the Volume Master Key (VMK), but the VMK shifts to disk storage, protected by an Intermediate Key (IK). <\/p>\n This IK, in turn, is TPM-encrypted using a Stretched Key (SK) derived from the user\u2019s PIN, ensuring dual authentication: unsealing the IK and deriving decryption keys.<\/p>\n This design thwarts brute-force attacks online via TPM lockouts, offline through randomized intermediates, but assumes secure hardware isolation.<\/p>\n Experiments by<\/a> Guillaume Qu\u00e9r\u00e9 on an HP ProBook 440 G1 revealed a discrete Nuvoton NPCT760HABYX TPM communicating over SPI, a shared bus easily tapped via nearby MX25U memory chip test points.<\/p>\n No soldering needed; just pins for clock, MOSI, and MISO lines, with CS optional for modern analyzers. Signal capture began pre-PIN entry using a DSLogic Plus analyzer, but quirks emerged: the clock idled high at intermediate voltages, distorting readings.<\/p>\n A simple 4.7k\u03a9 pulldown resistor grounded it, stabilizing the 33MHz SPI bus. Yet, TIS protocol anomalies persisted double bytes per packet, likely from slow acknowledgments, crippling automated decoders.<\/p>\n Manual decoding proved essential. Filtering raw MOSI\/MISO data with regexes stripped TIS wrappers (e.g., \u201c00 D4 00 18 XX\u201d for master requests), isolating TPM2.0 commands via headers like \u201c80 01\u201d (plain) or \u201c80 02\u201d (authenticated). <\/p>\n Captures, starting at PIN prompt, narrowed to key exchanges: ReadPublic for TPM keys, Load for objects, GetRandom for nonces, StartAuthSession, PolicyAuthValue\/PCR for policies, and crucially, Unseal for the IK blob. <\/p>\n Interestingly, PINs never transmit to the TPM; they influence only the Unseal HMAC, an undocumented nuance verified across good\/bad PIN trials.<\/p>\n The Unseal response holds the encrypted IK, differing from non-PIN blobs due to PIN-derived SK. Deriving SK involves UTF-16LE PIN hashing, doubled SHA-256, then 1,048,576 rounds with disk salt compute-intensive but feasible.<\/p>\n AES-CCM decryption with SK yields the IK, which unlocks the VMK from disk metadata via tools like dislocker.<\/p>\n For the ProBook, Python code stretched the PIN \u201c67851922\u201d against salt \u201cc36496f98842c6fd9841de2ea743d5cf\u201d, decrypting the 44-byte IK payload. <\/p>\n Dislocker then mounted the volume read-write, enabling backdoors like overwriting sethc.exe with cmd.exe for Shift+5 privilege escalation. <\/p>\n Automated scripts, such as SPITkey.py or tpm_sniffing_pin.py, streamline this, parsing volumes directly or leveraging dislocker outputs.<\/p>\n This attack underscores discrete TPMs\u2019 false security; fTPM or PIN-plus-startup keys mitigate sniffing, though insiders remain risks. Enterprises should audit configurations beyond defaults.<\/p>\n Follow us on Google News<\/a>, LinkedIn<\/a>, and X<\/a> for daily cybersecurity updates. Contact us<\/a> to feature your stories.<\/strong><\/p>\n The post Decoding PIN-Protected BitLocker Through TPM SPI Analysis To Decrypt And Mount The Disks<\/a> appeared first on Cyber Security News<\/a>.<\/p>\n<\/div>\nUnraveling PIN-Protected BitLocker Mechanics<\/strong><\/h2>\n
![\"PIN](\"https:\/\/i0.wp.com\/blogger.googleusercontent.com\/img\/b\/R29vZ2xl\/AVvXsEj3HeKzsiWtCqRINVtzhmyIgLnkspBMaBHHLuR_u_pcmfvQLybZcbm2OHBMGNVQdbm3Qhw-axvaEQ56fqTMKi_Bftny4QmSZVqSh8kq46cTYKGSZ4whvn5gk5dKR850PKxEOyqaHj0FRhZ2ce_Y5UhmXwE-1O6F2WydAqT_pimOT-tq2lbOvtKGhZxLj9l3\/s16000\/pin%2520protected.webp?ssl=1\")