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Following a year-long operation by undercover FBI agents, a Maryland couple has been arrested and charged with attempting to sell US nuclear secrets to another country in exchange for cryptocurrency.

US Navy nuclear engineer Jonathan Toebbe, who held a top-secret security clearance, and his wife Diana were arrested Saturday in West Virginia by the FBI and Naval Criminal Investigative Service after the couple allegedly sold information concerning the design of nuclear-powered US warships “to a person they believed was a representative of a foreign power but was actually an undercover FBI agent,” according to a Department of Justice statement.

In a pair of court filings on Monday, the Justice Department said the Toebbes should stay behind bars before trial because there is a risk that the couple will flee or destroy evidence. The bare-bones court filings didn’t contain details explaining why prosecutors think the couple is a flight risk, but they noted that the charges could carry a potential sentence of life in prison. The couple hasn’t yet entered a plea, and their first hearing is scheduled for Tuesday in West Virginia federal court.

The Washington Post first reported on the alleged espionage plot.

The Justice Department said Jonathan Toebbe had access to information on naval nuclear propulsion and sensitive military design elements including “operating parameters and performance characteristics of the reactors for nuclear powered warships.”

An FBI agent in a criminal complaint justifying the arrest alleges Toebbe first sent a package to a foreign government in April 2020 offering to sell the nuclear secrets, and an undercover FBI agent responded several months later via an encrypted email program and corresponded with him. The agent worked on gaining Toebbe’s trust before he allegedly agreed to sell the information for thousands of dollars in cryptocurrency, according to the complaint.

According to the complaint, the FBI “conducted an operation in the Washington, D.C. area that involved placing a signal at a location associated with (the foreign government) in an attempted effort to gain bona fides with ‘ALICE,’” the name Toebbe used as an alias when penning emails.

During what Toebbe believed to be a “dead drop,” or a hiding spot spies use to secretly pass information, the FBI said it arrested Jonathan and Diana on Saturday after Jonathan “placed yet another SD card” with classified information at a pre-arranged location in West Virginia. The couple has been charged with violations of the Atomic Energy Act, which prohibits anyone with access to classified information from sharing that information. The complaint claims the Toebbes attempted to “communicate, transmit, and disclose the same to another person with the intent to injure the United States and to secure an advantage to a foreign nation.”

It is unclear whether the couple has retained legal counsel yet.

Building trust

In one trust-building move during the lengthy correspondence, the FBI arranged to deliver a signal to Toebbe from a building that houses the unnamed country’s diplomats.

After gaining Toebbe’s trust, the agent tried to convince Toebbe to meet in person, but Toebbe was worried about being caught. The agent suggested using a dead drop at a location of his choosing. In March 2021, Toebbe allegedly wrote, “I am concerned that using a dead drop location your friend prepares makes me very vulnerable. If other interested parties are observing the location, I will be unable to detect them.”

Toebbe also said he was worried about receiving cash payments, because serial numbers can be traced, and he worried “tracking devices and other nasty surprises must be considered as well,” according to the FBI’s criminal complaint.

In April 2021, Toebbe allegedly wrote, “Is there some physical signal you can make that proves your identity to me? I could plan to visit Washington D.C. over the Memorial Day weekend. I would just be another tourist in the crowd. Perhaps you could fly a signal flag on your roof? Something easily observable from the street, but nothing to arouse an adversaries (sic) suspicion?”

The undercover agent replied, “We will set a signal from our main building observable from the street. It will bring you comfort with signal on display from area inside our property that we control and not a [sic] adversary. If you agree please acknowledge.”

Toebbe instead allegedly suggested using the decentralized cryptocurrency Monero because it “gives both us excellent deniability.” In an email cited in the complaint, Toebbe allegedly said he would deliver an SD card, containing several hundred pages of technical data. Once he confirmed receipt of the cryptocurrency, Toebbe allegedly wrote, “I will give you the passphrase.”

Toebbe also allegedly told the agent he would never use “the same drop location twice. I will give you a new Monero address each time. The decryption key will be different each time. No patterns for third parties to observe. The only electronic footprints will be Proton to Proton, so there is less risk of encrypted traffic being collected for future analysis by third parties. That part is not perfect. Perhaps as our friendship develops we will change addresses periodically?”

In June 2021, Toebbe and his wife traveled to West Virginia where the FBI said Toebbe “placed an SD card concealed within half a peanut butter sandwich at a pre-arranged ‘dead drop’ location.”

After retrieving the SD card, the undercover agent sent Toebbe a $20,000 cryptocurrency payment and Toebbe responded with the description key for the card, according to the complaint. The FBI said it “opened the provided SD card and provided the contents” to a US Navy subject matter expert, who confirmed it had classified information.

An ongoing correspondence

The FBI said Toebbe allegedly carried on the relationship with the undercover agent, making another dead drop in eastern Virginia in August 2021, where the FBI had him under surveillance as he left his house in Annapolis, Maryland, and drove to the dead drop.

The complaint said “the FBI observed JONATHAN TOEBBE service a dead drop in eastern Virginia. The FBI observed JONATHAN TOEBBE place an item in the container and remove a written message placed in the container by the FBI.”

“The FBI subsequently opened the SD card and provided the contents to the U.S. Navy subject matter expert. The U.S. Navy subject matter expert determined that multiple documents on the SD card contained Restricted Data. Specifically, the U.S. Navy subject matter expert determined that the document contained schematic designs for the Virginia-class submarine. Virginia-class submarines are nuclear-powered cruise missile fast-attack submarines, which incorporate the latest in stealth, intelligence gathering, and weapons systems technology,” the criminal complaint alleged.

In another exchange listed in the complaint, Toebbe explained how he obtained all of the classified information, saying, “I was extremely careful to gather the files I possess slowly and naturally in the routine of my job, so nobody would suspect my plan. We received training on warning signs to spot insider threats. We made very sure not to display even a single one. I do not believe any of my former colleagues would suspect me, if there is a future investigation.”

He also said, “I have considered the possible need to leave on short notice. Should that ever become necessary, I will be forever grateful for your help extracting me and my family. I surmise the first step would be unannounced travel to a safe third country with plans to meet your colleagues. We have passports and cash set aside for this purpose.” He said he hoped such a move would never prove necessary.

Toebbe said he hoped to one day to meet and have drinks with his foreign handler, writing unwittingly to the FBI agent, “Thank you for your partnership as well my friend. One day, when it is safe, perhaps two old friends will have a chance to stumble into each other at a cafe, share a bottle of wine and laugh over stories of their shared exploits. A fine thought, but I agree that our mutual need for security may make that impossible. Whether we meet or no[sic], I will always remember your bravery in serving your country and your commitment to helping me.”

This story has been updated with additional developments Monday.