MIT 'net policy wonks say decryption bill is unworkable

Researchers at the Massachusetts Institute of Technology (MIT) have called into question the ability of the Australian government to access encrypted communications without weakening security.

In a submission [pdf] to the Department of Home Affairs, MIT Internet Policy Research Initiative (IPRI) sought to address the technical drawbacks of proposed laws that will see service providers asked or compelled to assist law enforcement access encrypted communications.

The bill – which was first revealed in August and has now been altered to reflect some of the more than 14,000 submissions – indicates this could involve service providers building new tools, run government-built software, or facilitate access to targeted devices.

Home Affairs minister Peter Dutton has said this would not require provider to "build a decryption capability" or "create systemic weaknesses".

But the IPRI said there was “still an open question” around the possibility of designing a secure exceptional access (EA) system and that it has been unable “to find an EA design that would demonstrably avoid the introduction of systemic weaknesses or vulnerabilities” so far.

It also noted that “such a [EA] system cannot be reasoned about without the context of a specific set of functionality requirements and implementation parameters”.

“In other words, even given a useful specification, a full understanding of the security risks of any given EA design are still far off in the future,” it said, adding that this view was widely shared by the research community.

The researchers said that if the government went ahead with its plan to mandate technical capability requirements it should “begin by engaging with the technical community in developing methods and standards to evaluate the security risks of such requirements”.

Home Affairs claims to have consulted widely with industry ahead of releasing the bill, which had first been planned for 2018, to strike the right balance between service providers and law enforcement, though the extent of these discussions are unknown.

IPRI notes that “there must be a technical framework for evaluating those risks” and that it would be reasonable to expect that “there will be serious security hurdles to address” during the course of developing EA systems.

“Today, neither the United Kingdom’s Investigative Powers Act nor [Australia’s] proposed bill specifies clear technical or operational criteria against which Technical Capacity Notices are to be assessed,” it said.

“This is not a simple technical task, but is essential to assure that governments avoid mandates that could put national and even global infrastructure at risk.”

The submissions also indicates that “recognizing that there can be systemic risks associated with these requirements is an important public policy step”, contrary to Dutton's denial that systemic weaknesses can be introduced.

Transparency

The MIT researchers have also called on the government to introduce better transparency around the “design protocols, cryptographic algorithms, and software” that underpin the proposed assistance and access scheme.

This, they said, would “allow security researchers and the public to evaluate TCN [technical capability notice] requests for systemic weaknesses and vulnerabilities”, noting that these are often discovered by third parties such as Heartbleed.

“As the security research community has demonstrated over and over again, design flaws and implementation vulnerabilities in critical code is often discovered by third parties, not the engineers who design and implement the systems themselves,” the submission states.

“Hence, it is vital that the Bill encourage, not penalize, transparency of relevant details of any technical requirements that might be imposed.”

IPRI suggests that by imposing penalties for disclosing details of required changes to system design and implementation, the government will be risking otherwise addressable weaknesses through “the increasingly vital process of subjecting widely-used software to maximum public scrutiny”.

“Given the substantial concern that EA features can cause systemic security vulnerabilities, it is vital that the bill provide adequate transparency in two dimensions: 1) the ability for the public to have access to the technical details of the TCNs, and 2) the ability for providers subject to TCNs to disclose what they think is necessary about how their systems implement the TCNs.”

IPRI also asks that the large providers such as Apple, Microsoft, Google, WhatsApp and Signal “should not be forced to hide security features from their users”

“It would be a real and dangerous step backward for the security of the global Internet environment if vendors were forced to hide relevant security design details from their users and customers, IPRI said.”