Many Flash Drive manufactures are now selling compliant devices.  Most secure USB flash drives use some form of the Advanced Encryption Standard (AES) encryption, either 128-bit or 256-bit.  These levels are approved by the U.S. government for encrypting secret-level and top-secret-level documents and are HIPAA Compliant.  AES Security depends largely on the length and complexity of the password.  Most experts say a complex 16 to 20 character  password is required.