Crate libpep

libpep: Library for polymorphic pseudonymization and encryption

This library implements PEP cryptography based on ElGamal encrypted messages.

In the ElGamal scheme, a message M can be encrypted for a receiver which has public key Y associated with it, belonging to secret key y. Using the PEP cryptography, these encrypted messages can blindly be transcrypted from one key to another, by a central semi-trusted party, without the need to decrypt the message in between. Meanwhile, if the message contains an identifier of a data subject, this identifier can be pseudonymized. This enables end-to-end encrypted data sharing with built-in pseudonymization. Additionally, since at time of initial encryption, the future recipient does not need to be specified, data sharing can be done asynchronously, which means that encrypted data can be stored long-term before it is shared at any point in the future.

This library provides both a [low-level] API for ElGamal encryption and the PEP primitives, and a [high-level] API for pseudonymization and rekeying (i.e. transcryption) of Pseudonyms and DataPoints using this cryptographic concept.

The PEP framework was initially described in the article by Eric Verheul and Bart Jacobs, Polymorphic Encryption and Pseudonymisation in Identity Management and Medical Research. In Nieuw Archief voor Wiskunde (NAW), 5/18, nr. 3, 2017, p. 168-172. PDF

This library implements an extension of the PEP framework, called n-PEP, described in the article by Job Doesburg, Bernard van Gastel and Erik Poll (to be published).

Modules

• distributed
  Distributed n-PEP with wrappers for high-level PEPSystems (transcryptors) and PEPClients. This module is intended for use cases where transcryption is performed by n parties and trust is distributed among them (i.e. no single party is trusted but the system remains secure as long as at least 1 party remains honest).
• high_level
  High-level API specifying Pseudonyms and DataPoints, and transcryption (pseudonymization or rekeying) of their encrypted versions between different contexts. This module is intended for most use cases where a single trusted party (transcryptor) is responsible for pseudonymization and rekeying. The API is designed to be user-friendly and safe.
• internal
  Internal API that provides useful wrappers around dependencies, simplifying arithmetic operations. This module is not intended to be used by the end user, except for advanced use cases.
• low_level
  Low-level cryptographic primitives for ElGamal encryption and (n)-PEP operations. This module is intended for non-standard uses cases where the individual (n)-PEP primitives are needed.