The FBI has “hundreds of millions of dollars” to spend on developing technology for use in both national security and domestic law enforcement investigations — but it won’t reveal the exact amount.

Deputy Assistant Director of the FBI James Burrell spoke about the secretive budget of the Operational Technology Division — which focuses on all the bureau’s advanced investigative gizmos, from robots to surveillance tech to biometric scanners during a roundtable discussion on encryption technology.

In December 2015, The Washington Post reported the budget of the FBI’s Operational Technology Division at between $600 and $800 million, but officials refused to confirm the exact amount.

The FBI did not respond to a request for comment from The Intercept on the division’s budget.

The intelligence community sponsored the roundtable on Thursday and Friday to spark discussion among academics, scientists, developers, and tech officials on the finer points of encryption — and to try to answer whether it’s technically possible to give law enforcement access to secure devices without compromising digital security.

The National Academies of Science, Technology, and Medicine hosted the workshop, which included Chris Inglis, former deputy director of the NSA; James Baker, the top lawyer for the FBI; and tech officials from Apple, Microsoft, and other companies.

Burrell said the FBI divides its technical focuses into two areas: core IT capabilities, and the Operational Technology Division, which devotes resources to researching and developing technology “specifically for use in investigations.”

The division’s budget had to be put “into context,” Burrell stressed. Resources are split between tools developed for national security investigations versus domestic law enforcement. “Sometimes we’re not able to use the technology we develop for one side equally on the other,” because some technology is classified, he said.

The FBI has tried to keep evidence gleaned from its advanced, national security technology secret in court proceedings relating to domestic investigations — technology like Stingrays, which mimic cell phone towers to track location information of an entire geographical area. The FBI has even chosen to throw out legal prosecutions to hide its technical capabilities — a controversial decision that’s been criticized by advocates for transparency.

The bureau has also repeatedly stressed how challenging and expensive it is to develop capabilities to hack into devices rather than have a mandated access point in encryption. “Hacking devices, … of course we do it, but it is slow,” Baker said in his concluding remarks. “It’s expensive, it’s very fragile.”

The FBI has requested over $100 million more dollars for its operational technology division and cyber division for 2017 — pushing the grand total closer to a billion, if the Washington Post‘s figure is accurate. The FBI asked for over $85 million to bulk up its cyber offense and defense — and over $38 million to counter the problem encryption and other anonymity software poses during investigations through technological means.

“Of all kinds of government secrecy, budget secrecy is the least defensible,” Steven Aftergood, director of the Project on Government Secrecy run by the Federation of American Scientists, wrote in an email to The Intercept. Publishing the budget is required by the Constitution, he pointed out.

Agencies often prefer not to divulge budget in order keep some programs below the radar, or because keeping the amounts secret “helps to obscure large increases or decreases in funding that could attract unwanted attention,” he said.

“But spending levels do not reveal operational information — about targets, or capabilities, or vulnerabilities — and therefore they should almost always be disclosed,” he concluded.

The work done by the Operational Technology Division had received more attention after the 2015 San Bernadino shootings. Access to encrypted communications has become a national issue following the FBI’s battle with Apple over obtaining access to the San Bernardino shooter’s phone, which was encrypted.

Technology officials largely agree that giving any sort of “exceptional access” to software would damage an already fragile digital security regime experts have spent decades trying to improve.

During the first panel session, the conversation turned to what the FBI might be able to do instead of supporting mandated “backdoors” or security holes in products in order to intercept communications of suspects.

Baker, the bureau’s top lawyer, said the FBI’s technical capabilities are “finite” but “in some ways” are “better and increasing every day.”