Cryptographic locks guarding the secret files of a Brazilian banker suspected of financial crimes have defeated law enforcement officials.

Brazilian police seized five hard drives when they raided the Rio apartment of banker Daniel Dantas as part of Operation Satyagraha in July 2008. But subsequent efforts to decrypt files held on the hardware using a variety of dictionary-based attacks failed even after the South Americans called in the assistance of the FBI.

The files were encrypted using Truecrypt and an unnamed algorithm, reportedly based on the 256-bit AES standard. In the UK, Dantas would be compelled to reveal his passphrase under threat of imprisonment, but no such law exists in Brazil.