On Tuesday, the American Civil Liberties Union filed a new lawsuit demanding information about the FBI’s Electronic Device Analysis Unit (EDAU) — a forensic unit that the ACLU believes has been quietly breaking the iPhone’s local encryption systems.

“The FBI is secretly breaking the encryption that secures our cell phones and laptops from identity thieves, hackers, and abusive governments,” the ACLU said in a statement announcing the lawsuit, “and it refuses to even acknowledge that it has information about these efforts.”

The FBI has made few public statements about the EDAU, but the lawsuit cites a handful of cases in which prosecutors have submitted a “Mobile Device Unlock Request” and received data from a previously locked phone. The EDAU also put in public requests for the GrayKey devices that found success unlocking a previous version of iOS.

In June 2018, the ACLU filed a FOIA request for records relating to the EDAU, but the FBI has refused to confirm any records even exist. After a string of appeals within the FOIA process, the group is taking the issue to federal court, calling on the attorney general and FBI inspector general to directly intervene and make the records available.

“We’re demanding the government release records concerning any policies applicable to the EDAU, its technological capabilities to unlock or access electronic devices, and its requests for, purchases of, or uses of software that could enable it to bypass encryption,” the ACLU said in a statement.

For years, Apple has promoted its iOS disk encryption as a powerful protection against identity theft and unauthorized access — a crucial reassurance as more and more sensitive data is routed through our phones. Apple’s insistence on robust data security has brought it into conflict with the FBI, which has repeatedly pressured the company to build a backdoor into its system, most notably in the San Bernardino case. The FBI’s current capability to break iOS encryption remains unclear.