DIMACS Workshop 2019 A universal MPC machine* Dragoș Rotaru University of Bristol, KU Leuven *MArBled Circuits: Mixing Arithmetic and Boolean Circuits with Active Security; • Joint work with Tim Wood. • https://ia.cr/2019/207 Dragoș Rotaru 1 imec-Cosic, Dept. Electrical Engineering
What is multiparty computation? a c b Goal : Compute F(a, b, c) Dragos Rotaru 2 Dragoș Rotaru 2 imec-Cosic, Dept. Electrical Engineering
How can we achieve MPC? Secret Sharing Garbled Circuits Fast networks (LAN) Slow Networks (WAN) Arithmetic/Boolean circuits Boolean circuits Low depth, many AND gates Large depth, few AND gates Dragoș Rotaru 3 imec-Cosic, Dept. Electrical Engineering
Can we switch between? A (GMW mod 2 𝑙 ) Yao GC – mod 2 B (GMW mod 2) ABY [DMZ’15] Dragoș Rotaru 4 imec-Cosic, Dept. Electrical Engineering
Can we switch between? A (GMW mod 2 𝑙 ) Yao GC – mod 2 B (GMW mod 2) ABY [DMZ’15] ABY3 [MR’18] Dragoș Rotaru 5 imec-Cosic, Dept. Electrical Engineering
Can we switch between? A (GMW mod 2 𝑙 ) Yao GC – mod 2 B (GMW mod 2) ABY [DMZ’15] ABY3 [MR’18] Dragoș Rotaru 6 imec-Cosic, Dept. Electrical Engineering
What about dishonest majority? Dragoș Rotaru 7 imec-Cosic, Dept. Electrical Engineering
What about dishonest majority? SPDZ SPDZ-BMR Dragoș Rotaru 8 imec-Cosic, Dept. Electrical Engineering
What about dishonest majority? Naive >110K ANDs SPDZ SPDZ-BMR Dragoș Rotaru 9 imec-Cosic, Dept. Electrical Engineering
What about dishonest majority? Naive >110K ANDs SPDZ SPDZ-BMR >110K ANDs Dragoș Rotaru 10 imec-Cosic, Dept. Electrical Engineering
What about dishonest majority? Naive <1K ANDs SPDZ SPDZ-BMR 0 ANDs Dragoș Rotaru 11 imec-Cosic, Dept. Electrical Engineering
How general is this? 𝐆 𝑞 SPDZ SPDZ-BMR WRK’17 𝐚 2 𝑙 HSS’17 SPDZ Dragoș Rotaru 12 imec-Cosic, Dept. Electrical Engineering
How general is this? 𝐆 𝑞 SPDZ SPDZ-BMR WRK’17 𝐚 2 𝑙 HSS’17 SPDZ Dragoș Rotaru 13 imec-Cosic, Dept. Electrical Engineering
How general is this? 𝐆 𝑞 SPDZ SPDZ-BMR WRK’17 𝐚 2 𝑙 HSS’17 SPDZ Dragoș Rotaru 14 imec-Cosic, Dept. Electrical Engineering
How general is this? 𝐆 𝑞 SPDZ SPDZ-BMR WRK’17 𝐚 2 𝑙 HSS’17 SPDZ Any honest majority protocol Dragoș Rotaru 15 imec-Cosic, Dept. Electrical Engineering
Our focus 𝐆 𝑞 SPDZ SPDZ-BMR WRK’17 𝐚 2 𝑙 HSS’17 SPDZ Dragoș Rotaru 16 imec-Cosic, Dept. Electrical Engineering
Malicious MPC protocols Preprocessing Online phase phase PKC Inputs SPDZ, TinyOT, BDOZa , MASCOT, WRK’17, HSS’17, … Dragoș Rotaru 17 imec-Cosic, Dept. Electrical Engineering
Let’s talk about 𝐆 𝑞 SPDZ Dragoș Rotaru 18 imec-Cosic, Dept. Electrical Engineering
SPDZ online phase 𝐆 𝑞 SPDZ α 1 α 2 + α 3 + α = 𝑦 3 𝑦 1 𝑦 2 𝑦 + + = γ(𝑦) 1 γ(𝑦) 2 + + γ(𝑦) 3 α 𝑦 = Dragoș Rotaru 19 imec-Cosic, Dept. Electrical Engineering
SPDZ online phase 𝐆 𝑞 SPDZ α 1 α 2 + α 3 + α = 𝑦 1 + 𝑧 1 𝑦 2 + 𝑧 2 𝑦 + 𝑧 𝑦 3 + 𝑧 3 + + = γ x 1 + γ y 1 γ x 2 + γ y 2 + γ x 3 + γ y 3 + α ( 𝑦 + 𝑧) = Dragoș Rotaru 20 imec-Cosic, Dept. Electrical Engineering
SPDZ online phase 𝐆 𝑞 SPDZ ← X 𝐵 X 𝐵 Retrieve a random mask Input Dragoș Rotaru 21 imec-Cosic, Dept. Electrical Engineering
SPDZ online phase 𝐆 𝑞 SPDZ ← X 𝐵 X 𝐵 Input Dragoș Rotaru 22 imec-Cosic, Dept. Electrical Engineering
SPDZ online phase 𝐆 𝑞 SPDZ ← X 𝐵 X 𝐵 Input ← x x Open Dragoș Rotaru 23 imec-Cosic, Dept. Electrical Engineering
SPDZ online phase 𝐆 𝑞 SPDZ ← X 𝐵 X 𝐵 Input ← x x Open MAC Check Dragoș Rotaru 24 imec-Cosic, Dept. Electrical Engineering
SPDZ online phase 𝐆 𝑞 SPDZ ← X 𝐵 X 𝐵 Input ← x x Open ← XOR Retrieve a Beaver triple z x y Dragoș Rotaru 25 imec-Cosic, Dept. Electrical Engineering
SPDZ online phase 𝐆 𝑞 SPDZ ← X 𝐵 X 𝐵 Input ← x x Open MAC Check ← XOR z x y Dragoș Rotaru 26 imec-Cosic, Dept. Electrical Engineering
Let’s talk about 𝐆 2 SPDZ-BMR Dragoș Rotaru 27 imec-Cosic, Dept. Electrical Engineering
SPDZ online phase 𝐆 2 SPDZ-BMR A B AND AND C A B C Dragoș Rotaru 28 imec-Cosic, Dept. Electrical Engineering
SPDZ online phase 𝐆 2 SPDZ-BMR A B AND AND C MAC Check Λ 𝑑 ←C + λ 𝑑 Λ 𝐵 ← A + λ 𝑏 Λ 𝐶 ← B + λ 𝑐 Dragoș Rotaru 29 imec-Cosic, Dept. Electrical Engineering
SPDZ online phase 𝐆 2 SPDZ-BMR A B AND AND C MAC Check Λ 𝑑 ←C + λ 𝑑 Λ 𝐵 ← A + λ 𝑏 Λ 𝐶 ← B + λ 𝑐 Inputs - cheap XOR - free Mod p arithmetic - some AND gates Dragoș Rotaru 30 imec-Cosic, Dept. Electrical Engineering
Main idea: 𝐆 𝑞 𝐆 2 SPDZ SPDZ-BMR x x x Dragoș Rotaru 31 imec-Cosic, Dept. Electrical Engineering
Main idea: 𝐆 𝑞 𝐆 2 SPDZ SPDZ-BMR x x x r Dragoș Rotaru 32 imec-Cosic, Dept. Electrical Engineering
Main idea: 𝐆 𝑞 𝐆 2 SPDZ SPDZ-BMR x x - x-r x r Open SPDZ – MAC Check Dragoș Rotaru 33 imec-Cosic, Dept. Electrical Engineering
Main idea: 𝐆 𝑞 𝐆 2 SPDZ SPDZ-BMR x x - + r x x-r x r Dragoș Rotaru 34 imec-Cosic, Dept. Electrical Engineering
Introducing daBits Dragoș Rotaru 35 imec-Cosic, Dept. Electrical Engineering
Introducing daBits 𝐆 𝑞 𝐆 2 SPDZ SPDZ-BMR 𝒄 𝑩 𝒄 𝑪 𝒄 𝑫 Dragoș Rotaru 36 imec-Cosic, Dept. Electrical Engineering
Introducing daBits 𝐆 𝑞 𝐆 2 SPDZ SPDZ-BMR SPDZ Input SPDZ-BMR Input 𝒄 𝑩 𝒄 𝑪 𝒄 𝑫 Dragoș Rotaru 37 imec-Cosic, Dept. Electrical Engineering
Introducing daBits 𝐆 𝑞 𝐆 2 SPDZ SPDZ-BMR SPDZ Input SPDZ-BMR Input 𝒄 𝑩 𝒄 𝑩 𝒄 𝑪 𝒄 𝑪 𝒄 𝑫 𝒄 𝑫 Dragoș Rotaru 38 imec-Cosic, Dept. Electrical Engineering
Introducing daBits 𝐆 𝑞 𝐆 2 SPDZ SPDZ-BMR SPDZ Open SPDZ-BMR Open 𝒄 𝑩 𝒄 𝑩 𝒄 𝑪 𝒄 𝑪 𝒄 𝑫 𝒄 𝑫 Dragoș Rotaru 39 imec-Cosic, Dept. Electrical Engineering
Introducing daBits 𝐆 𝑞 𝐆 2 SPDZ SPDZ-BMR SPDZ XOR SPDZ-BMR XOR 𝒄 𝑩 𝒄 𝑪 𝒄 𝑫 𝒄 𝑩 𝒄 𝑪 𝒄 𝑫 Dragoș Rotaru 40 imec-Cosic, Dept. Electrical Engineering
Introducing daBits 𝐆 𝑞 𝐆 2 SPDZ SPDZ-BMR SPDZ Open SPDZ-BMR Open 𝒄 𝑩 𝒄 𝑪 𝒄 𝑫 𝒄 𝑩 𝒄 𝑪 𝒄 𝑫 Dragoș Rotaru 41 imec-Cosic, Dept. Electrical Engineering
daBit cost SPDZ-BMR SPDZ Dragoș Rotaru 42 imec-Cosic, Dept. Electrical Engineering
Preprocessing cost per conversion Dragoș Rotaru 43 imec-Cosic, Dept. Electrical Engineering
Example code in MP-SPDZ Dragoș Rotaru 44 imec-Cosic, Dept. Electrical Engineering
Online cost per conversion 8X overhead than using ABY Dragoș Rotaru 45 imec-Cosic, Dept. Electrical Engineering
Online cost per conversion 8X overhead than using ABY Dragoș Rotaru 46 imec-Cosic, Dept. Electrical Engineering
What’s next? • SCALE- MAMBA has WRK’17. • It also has all preprocessing phases connected – ideal candidate for daBits in a more realistic system. • Moral: Stitch your work together so it would be easier to build more efficient protocols on top of them. Dragoș Rotaru 47 imec-Cosic, Dept. Electrical Engineering
Thank you! Dragoș Rotaru 48 imec-Cosic, Dept. Electrical Engineering
Thank you! • Questions? • https://ia.cr/2019/207 Dragoș Rotaru 49 imec-Cosic, Dept. Electrical Engineering
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