Welcome to the home page of the COST Training School on Symmetric Cryptography and Blockchain that will take place in Torremolinos (Spain) from 19th until 23rd February 2018.

The training school will be co-organised with the COST action IC1306 “Cryptography for Secure Digital Interaction” and will contain lectures on symmetric cryptography as well as lectures and discussions on blockchain technologies.

It will be held in the Meliá Costa del Sol Hotel.


One of the focuses of the school will be on modes of operation and authenticated encryption. Many applications require to guarantee both confidentiality and integrity of the data. A standard algorithm for symmetric encryption consists in using a block cipher, typically the AES, together with a mode of operation (e.g. CBC or CTR) which enables to handle variable-length messages. There is no such solution for authenticated encryption which is satisfactory both in terms of performance and security. Therefore, the on-going Caesar competition has been launched in 2014 in order to design and analyze new authenticated encryption schemes suitable for widespread adoption.

The lectures will be organised as follows: The first part [lecture + exercises] will be on symmetric cryptography including design and cryptanalysis of block ciphers. We will include lectures on the classic block cipher design principle as well as some new trends like ciphers with minimal multiplicative complexity suitable for MPC applications. We will also have lectures on modes of operation for encryption (CBC, CTR, and beyond-birthday modes), from an attack perspective. The aim is to describe these modes, analyse their security, detail the role of the IV (random IV, stateful setting) and present some generic attacks against modes. Next, we will provide lectures and exercises on authenticated encryption mainly from a provable-security perspective. Generic composition of authentication and encryption; discussion on the security of the GCM mode; presentation of more recent proposals.

One of the hot topics in cryptology at the moment is blockchain. Bitcoin is the first example of a blockchain and it has spawned a lot of attention. A block chain is constructed using a cryptographic hash function. Cryptologists do not seem to agree on the impact and importance of the blockchain technology. We intend to have a session in our school with different views on the topic.


The goal of the school is to give students a thorough introduction to the state-of-the-art within symmetric cryptology covering both the theoretical side (design and cryptanalysis of symmetric cryptographic primitives and provable security) and the practical side (practical cryptanalysis in exercise sessions). The school will have two streams: basic principles of symmetric cryptography and advanced topics, like modes of operation, authenticated encryption and blockchain technologies.

The school will be suitable for Master students with background in cryptography and security; PhD students and security experts from industry. There is no requirements or pre-selection of the participants before registering to the school unless you apply for a stipend (see next section).


We have a limited number of stipends for applicants from countries who joined the COST CryptoAction (see here for the list). The stipend is a fixed amount of 800 Euro (500 Euro for Spain). Gender and country balance will be taken into account when evaluating stipend applications. The deadline for stipend application is 1st of November, 2017. The students who did not qualify for a stipend can still register to the school by paying the registration fee.

In order to apply for a stipend, please fill in the Google form here before 1st of November, 2017. The applicants will be informed by 10th of November and will have to book their hotel rooms no later than 30th of November in order to use the pre-booked rooms. Note that after 30th of November rooms will not be guaranteed and reservations will be subject to availability.

Latest news

  • Registration is open (25th October 2017)
  • Information about stipends application added (1st October 2017)
  • Accommodation guidelines are online (27th September 2017)
  • List of confirmed speakers is online (26th September 2017)
  • Website is online (17th August 2017)