Federal investigators say they accessed encrypted Signal messages sent before the January 6, 2021 riots in the US Capitol and used them as evidence to indict the leader of Oath Keepers, an extremist militia group. far-right. and others accused in a seditious plot.

In a new legal complaint released Thursday, the Justice Department alleges that the defendants conspired to vigorously oppose the transfer of power between then-President Donald Trump and Joe Biden, even attempting to seize control of the United States Capitol. United.

The complaint refers to numerous messages sent on Signal, an end-to-end encrypted messaging app, raising questions about how authorities accessed them and recalling a long-standing point of tension between the law enforcement community and the tech industry. Encryption scrambles messages so that no one can read them except the intended recipients, including the platform that hosts the messages.

It is not clear how the researchers gained access to the messages. Representatives for Signal, the Department of Justice and the Federal Bureau of Investigation did not immediately respond to requests for comment from CNBC.

One possibility is that another recipient with access to the messages has delivered them to the researchers. The complaint refers to group messages that are run in the application, so it is possible that another participant in those chats has cooperated.

Encryption has been a point of contention among researchers and tech companies for years. While law enforcement agencies worry criminals exploit encrypted technology to hide wrongdoing, tech companies like Apple have argued that it is an important privacy tool. In the past, law enforcement agencies have tried to get tech companies to unlock their devices to aid in serious crime investigations, but companies like Apple argue that if they break encryption for American investigators, they will compromise the entire system and potentially leave space. for foreign adversaries to exploit weaknesses.

The problem rose to prominence in 2015, when Apple refused to crack the encryption on a suspect’s iPhone after a mass shooting in San Bernardino, California. After a tense standoff, the researchers were finally able to crack the encryption themselves.

But some law enforcement officials have said that newer security features in iPhone software now make it difficult for them to technically access those devices, even if they can get a warrant.

The problem resurfaced under the Trump administration, even as Meta, then known as Facebook, announced plans to bundle all of its messaging services together and end-to-end encryption. Law enforcement agencies said the plans would hamper their ability to clamp down on child sexual abuse material on the platform.