Transparent decryption is a method of decrypting data which unavoidably produces evidence that the decryption operation has taken place. The idea is to prevent the covert decryption of data. In particular, transparent decryption protocols allow a user Alice to share with Bob the right to access data, in such a way that Bob may decrypt at a time of his choosing, but only while simultaneously leaving evidence for Alice of the fact that decryption occurred. Transparent decryption supports

privacy Privacy (, ) is the ability of an individual or group to seclude themselves or information about themselves, and thereby express themselves selectively. The domain of privacy partially overlaps with security, which can include the concepts of a ...

, because this evidence alerts data subjects to the fact that information about them has been decrypted and disincentivises data misuse.

Applications

Transparent decryption has been proposed for several systems where there is a need to simultaneously achieve accountability and secrecy. For example: * In lawful interception, law enforcement agencies can access private messages and emails. Transparent decryption can make such accesses accountable, giving citizens guarantees about how their private information is accessed. * Data arising from

vehicle A vehicle () is a machine designed for self-propulsion, usually to transport people, cargo, or both. The term "vehicle" typically refers to land vehicles such as human-powered land vehicle, human-powered vehicles (e.g. bicycles, tricycles, velo ...

s and IoT devices may contain personal information about the vehicle or device owners and their activities. Nevertheless, the data is typically processed in order to provide user functionality and also to investigate and fight crime. Transparent decryption can be used to help users monitor when and how data about them is being accessed and used.

Implementation

In transparent decryption, the

decryption key A key in cryptography is a piece of information, usually a string of numbers or letters that are stored in a file, which, when processed through a cryptographic algorithm, can encode or decode cryptographic data. Based on the used method, the key ...

distributed Distribution may refer to: Mathematics *Distribution (mathematics), generalized functions used to formulate solutions of partial differential equations *Probability distribution, the probability of a particular value or value range of a varia ...

among a set of agents (called trustees); they use their key share only if the required transparency conditions have been satisfied. Typically, the transparency condition can be formulated as the presence of the decryption request in a

distributed ledger A distributed ledger (also called a shared ledger or distributed ledger technology or DLT) is a system whereby replicated, shared, and synchronized digital data is geographically spread (distributed) across many sites, countries, or institutions. I ...

Alternative solutions

Besides transparent decryption, some other techniques have been proposed for achieving law enforcement while preserving privacy. * Solutions that allow competing parties to unify their data access policies. ''Attribute-based encryption with oblivious attribute translation'' (OTABE) is an extension of

attribute-based encryption Attribute-based encryption is a generalisation of public-key encryption which enables fine grained access control of encrypted data using authorisation policies. The secret key of a user and the ciphertext are dependent upon attributes (e.g. thei ...

that allows translation between proprietary

attributes Attribute may refer to: * Attribute (philosophy), a characteristic of an object * Attribute (research), a quality of an object * Grammatical modifier In linguistics, a modifier is an optional element in phrase structure or clause structure whic ...

belonging to different organisations, and it has been applied to the problem of law-enforcement access to phone call

metadata Metadata (or metainformation) is "data that provides information about other data", but not the content of the data itself, such as the text of a message or the image itself. There are many distinct types of metadata, including: * Descriptive ...

. * Solutions that rely on sophisticated

cryptography Cryptography, or cryptology (from "hidden, secret"; and ''graphein'', "to write", or ''-logy, -logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of Adversary (cryptography), ...

, such as

zero-knowledge proof In cryptography, a zero-knowledge proof (also known as a ZK proof or ZKP) is a protocol in which one party (the prover) can convince another party (the verifier) that some given statement is true, without conveying to the verifier any information ...

s that the actions of law enforcement is consistent with judge rulings and the actions of companies, and

multi-party computation Secure multi-party computation (also known as secure computation, multi-party computation (MPC) or privacy-preserving computation) is a subfield of cryptography with the goal of creating methods for parties to jointly compute a function over their ...

to compute results.

References

{{reflist Cryptography Data protection Information privacy