The Tor browser

[Jehanne]

Tails, LUKS and TrueCrypt are secure; here's an example of where the FBI was not able to decrypt a suspect's hard drive:

Operation Satyagraha

In July 2008, several TrueCrypt-secured hard drives were seized from Brazilian banker Daniel Dantas, who was suspected of financial crimes. The Brazilian National Institute of Criminology (INC) tried unsuccessfully for five months to obtain access to his files on the TrueCrypt-protected disks. They enlisted the help of the FBI, who used dictionary attacks against Dantas' disks for over 12 months, but were still unable to decrypt them.[90][91]

Operation_Satyagraha

VeraCrypt is even more secure:

VeraCrypt

And, the Tor Browser, when used properly, is secure:

Tor has been praised for providing privacy and anonymity to vulnerable Internet users such as political activists fearing surveillance and arrest, ordinary web users seeking to circumvent censorship, and people who have been threatened with violence or abuse by stalkers.[176][177] The U.S. National Security Agency (NSA) has called Tor "the king of high-secure, low-latency Internet anonymity",[15] and BusinessWeek magazine has described it as "perhaps the most effective means of defeating the online surveillance efforts of intelligence agencies around the world".[178] Other media have described Tor as "a sophisticated privacy tool",[179] "easy to use"[180] and "so secure that even the world's most sophisticated electronic spies haven't figured out how to crack it".[73]

Tor Browser Security