BiFi

Private Key Leakage

Estimated loss

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VERDICT —OUT OF SCOPE

Root cause is private-key / signer compromise — the on-chain contract behaved exactly as written. No pre-deployment source audit or bytecode review reaches the key-custody perimeter; this is operational-security territory (HSM/MPC hygiene, key rotation, hot-wallet isolation). Bytecode would show nothing wrong.

▰ METHOD

PRIVATE KEY

PRIVATE-KEY

Root cause

Root-cause analysis not yet published. The incident description below contains all currently available signal — review the attack transaction directly for definitive forensics.

Forensic narrative

BIFROST officially released a report saying that the BTC address registration server of the BiFi service was attacked. According to the analysis, the attack was limited to the BTC address registration server, and neither the smart contract nor the BiFi protocol detected the vulnerability. BiFi issues and uses an address for each user who deposits BTC. The deposit addresses are signed and delivered to the address issuing server and the addresses are reflected on BiFi only in the case when the signature is verified. In the attack, the server key of the address issuing server was exposed and the attacker was able to self-sign their own deposit address. Since the attacker could generate a valid signature on the deposit address, BiFi mistakenly recognized the attacker’s BTC transfer as a BTC deposit into BiFi. As a result, the attacker was able to borrow 1,852 ETH with fake deposit. Attack method (per SlowMist): Private Key Leakage. Reported loss: 1,852 ETH.

Primary source

https://bifrost.medium.com/post-mortem-bifi-btc-illegal-address-registration-c21ce3ba9fc8 ↗

Sourced from

slowmist

Technical record