Scalable Cryptography

AbstractIn our modern digital society, cryptography is vital to protect the secrecy and integrity of transmitted and stored information. Settings like digital commerce, electronic banking, or simply private email communication already rely on encryption and signature schemes.However, today’s cryptographic schemes do not scale well, and thus are not suited for the increasingly large sets of data they are used on. For instance, the security guarantees currently known for RSA encryption—one of the most commonly used type of public-key encryption scheme—degrade linearly in the number of users and ciphertexts. Hence, larger settings (such as cloud computing, or simply the scenario of encrypting all existing email traffic) may enable new and more efficient attacks. To maintain a reasonable level of security in larger scenarios, RSA keylengths must be chosen significantly larger, and the scheme becomes very inefficient. Besides, a switch in RSA keylengths requires an update of the whole public key infrastructure, an impossibility in truly large scenarios. Even worse, when the scenario grows beyond an initially anticipated size, we may lose all security guarantees.This problematic is the motivation for our project “Scalable Cryptography”, which aims at offering a toolbox of cryptographic schemes that are suitable for huge sets of data. In this overview, we summarize the approach, and the main findings of our project. We give a number of settings in which it is possible to indeed provide scalable cryptographic building blocks. For instance, we survey our work on the construction of scalable public-key encryption schemes (a central cryptographic building block that helps secure communication), but also briefly mention other settings such as “reconfigurable cryptography”. We also provide first results on scalable quantum-resistant cryptography, i.e., scalable cryptographic schemes that remain secure even in the presence of a quantum computer.