Yuxian Analyzes Coldcard Vulnerability: Passphrase Can Evade Attack
Security researcher Yuxian pointed out that in the Coldcard hardware wallet weak random number security incident, if the mnemonic uses a Passphrase, it can fortunately evade this wave of attacks.
He emphasized that the Passphrase is not the wallet unlock PIN, but a dedicated "password" set for the mnemonic under the BIP-39 standard (technically as a salt), derived through PBKDF2: seed = PBKDF2(password=mnemonic, salt="mnemonic"+passphrase, iterations=2048, PRF=HMAC-SHA512); importing the mnemonic without a Passphrase will show empty addresses, and only entering the correct Passphrase can derive the real asset address.
Mainstream hardware wallets generally support this mechanism, but most software wallets have yet to support it; users must remember the Passphrase itself, or they will permanently lose access, highlighting the critical protective value of an additional entropy layer in seed leakage scenarios.
Source: Public Information
ABAB AI Insight
Yuxian, as a long-time researcher focused on wallet and on-chain security, uses the insufficient seed entropy incident of Coldcard Mk3 and other models to re-popularize the BIP-39 Passphrase mechanism, pointing out that as a salt for the mnemonic, it can still protect assets when the main seed is subjected to brute force or weak entropy attacks.
In terms of capital and product pathways, hardware wallet manufacturers provide a "second line of defense" through Passphrase, motivated by reducing single point failure risks while encouraging users to migrate from basic mnemonics to higher security practices; the lack of software wallets exposes ecological stratification differences.
Analogous to multi-signature and hardware isolation, Passphrase exists at the practical level of "low-cost enhancement of self-custody security," rather than a new protocol.
Essentially, it is a technical alternative: when the base seed entropy may be insufficient, the additional user-controlled salt shifts security from "device random number dependency" to "user memory and operation," reconstructing the protective structure against single point failures.
ABAB News · Law of Cognition
- The mnemonic is the front door, the Passphrase is the back door.
- The salt turns the stolen seed into an empty shell.
- Remember one more word, lose one less coin.