The LowMC cryptanalysis challenge
The LowMC cryptanalysis challenge is a set of attack challenges on different LowMC block cipher instances. It offers an opportunity to cryptanalyze block ciphers differing from most traditional designs allowing you to apply techniques that might not be competetive on other block ciphers. Apart from fame, you can also win prizes.
For each challenge, there are two attack targets. The first is to find the most time efficient attack on a round-reduced version of the LowMC instance. The second challenge is to break a number of rounds deemed secure by the designers. For the first type of challenge, the prize will go the best time efficiency (and potentially extra prizes for low memory/data complexity). For the second type of challenge, the prize will go to whoever submits the first valid attack.
If you win a prize, you can choose a present from one of the countries of people involved in the design of LowMC: Austria, Denmark, Germany, Iran, and the United Kingdom.
Deadline: November 1st, 2017.
Challenges
The attack challenges cover three types of LowMC instantiations that are optimized with respect to different metrics:
- Challenge I: Minimizing total multiplications.
- Challenge II: Minimizing the multiplicative depth,
- Challenge III: Minimizing multiplications per encrypted bit.
Challenge I is the setting that is relevant for using LowMC in post-quantum signature schemes. Challenge II is the setting that is relevant for using LowMC in Fully Homomorphic Encryption. Challenge III is the setting most relevant for secure multi-party computation.
Challenge I
| Block size | Key size | S-boxes per round | data complexity |
|---|---|---|---|
| 256 | 256 | 1 | 1 |
Fast attack goal: 243 rounds
Cutting edge attack goal: 380 rounds
Challenge II
| Block size | Key size | S-boxes per round | data complexity |
|---|---|---|---|
| 256 | 128 | 85 | 1 |
Fast attack goal: 5 rounds
Cutting edge attack goal: 8 rounds
| Block size | Key size | S-boxes per round | data complexity |
|---|---|---|---|
| 256 | 128 | 85 | 128 |
Fast attack goal: 11 rounds
Cutting edge attack goal: 14 rounds
Challenge III
| Block size | Key size | S-boxes per round | data complexity |
|---|---|---|---|
| 1024 | 128 | 1 | 128 |
Fast attack goal: 600 rounds
Cutting edge attack goal: 901 rounds
Contact
If you have any questions, or want to submit an attack write to:
tyti (ett) dtu (dot) dk