The US National Security Agency (NSA) is building a quantum computer that could crack encryption that protects banking, medical, business and government records around the world.
In documents given to the US newspaper the Washington Post by whistleblower and former NSA contractor Edward Snowden, the spying agency wants to harness the potential speed of quantum computers to improve its code-cracking.
The project called Penetrating Hard Targets is said to cost approximately $80million (£49million), and is thought to be conducted out of a lab in Maryland.
If successful, the machine would be revolutionary, as all current forms of public key encryption would be scrambled, including on websites, for emails, and those used by foreign governments to protect their state secrets.
The documents indicate that the NSA is the organisation closest to building such a machine, in comparison to the wider scientific community's civilian labs.
It is understood that the NSA sees itself as equally advanced as the quantum computing labs sponsored by the European Union and the Swiss Government.
"The geographic scope has narrowed from a global effort to a discrete focus on the European Union and Switzerland," one NSA document states.
Scott Aaronson, an associate professor of electrical engineering and computer science at the Massachusetts Institute of Technology, told the Washington Post: "It seems improbable that the NSA could be that far ahead of the open world without anybody knowing it."
The NSA declined to comment to the US newpspaper.
The power of quantum computers comes in "quantum superposition". While regular computers use binary code - which are either zeroes or ones - a quantum computer would use qubits, which are simultaneously both zeroes and ones.
The process of creating the correct algorithms for this is yet to be achieved, as this area of quantum mechanics is barely understood.
Scientists are faced with the problem of keeping qubits stable enough to interact with each other in a way that can be harnessed usefully.
The documents indicate the NSA's researchers are having some success developing the basic building blocks for the machine.
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