Evidence Tampering Might Be Prevented With Blockchain, States UK Ministry Of Justice

On the government agency's blog on November 2, 2017, the Ministry of Justice (MoJ) takes a look at blockchain technology and cryptocurrencies, and says it is "keen to explore the potential uses within government."

The warm sentiment towards blockchain technology may stem from the ministry's assessment that the immutable ledger of such a network represents "a single source of truth" where there is "no need for everyone to ‘just trust’ a single authority—trust is distributed and decentralised amongst the users." It is a property the MoJ went on to say "could be genuinely transformational in situations where public trust of government might not be taken for granted."

Specifically, the MoJ is considering blockchain’s application to criminal prosecutions, evidence for which is often digital, such as videos, emails, electronic documents and data. The MoJ acknowledged that a robust verification mechanism must encompass these crucial forms of evidence and interface seamlessly with fast-paced modern digital society; blockchain-based systems may be the answer.

An example the MoJ provides involves footage from a policeman's bodycam gathered throughout the officer's shift. The MoJ estimates that a national program of such cameras would generate nearly a petabyte of information. (To put that into perspective, a petabyte is 1,000,000 gigabytes.) The massive amount of information would require a data management system, and given the capability of malicious actors to apply modern digital editing techniques to that footage, maintaining the veracity of its unchanged state is absolutely critical and poses a serious issue for authorities.

The MoJ's example examines how such footage could be broken into 10 minute segments and uploaded into a secure cloud service. It would go a long way towards ensuring the video footage is unaltered. According to the MoJ, "If that chunk of video were needed in court, it could be unambiguously, cryptographically verified that the chunk of video seen in court is exactly identical to that particular chunk recorded at that time, and has not been altered or processed in any way."

The cloud service the MoJ suggests provides the following functionality:

"1. Provides secure cloud storage & controlled access
2. Records metadata about each clip—which device it was from, where and when it was shot, etc.
3. Calculates a hash of the clip, and of the metadata
4. A hash is a mathematical function which generates a unique value of a known small size, for any size input—they are often used to ‘fingerprint’ data, as changing even one byte of the data would produce a different hash. Records the hashes of the clip and its metadata onto a blockchain. Note that the clip itself would not be on the blockchain, just a hash of its data and metadata, including a pointer to its location in the secure storage service."

While police are the only ones who would be able to write to such a hypothetical ledger, as an open public-facing system, anyone would be able to see the ledger of the blockchain to which police sent reports. The MoJ said that expanding the system to also allow other sources of evidence is conceivable, but beyond the scope of its current example.

While it is only conceptual, the MoJ’s "thought experiment" may yet be the first step towards creating a blockchain-based system of verification. Once such a system is implemented, the MoJ said, "even the most ardent conspiracy theorists could verify for themselves that the evidence has not been tampered with—there could be no possibility of records being falsified after the fact without detection."