Provable Security of (Tweakable) Block Ciphers Based on Substitution-Permutation Networks Benoit Cogliati Yevgeniy Dodis Jonathan Katz Jooyoung Lee John Steinberger John Steinberger Aishwarya Thiruvengadam Aishwarya Thiruvengadam Zhe Zhang Zhe Zhang 1
Block Ciphers • Building block for many cryptographic constructions • Hash functions Hash functions • Encryption schemes • Message authentication codes • Keyed permutations • Popular Design Paradigms • Feistel Networks • Feistel Networks • Substitution-Permutation Networks 2
Block Ciphers: Designs • Popular Design Paradigms • Feistel Network Feistel Network • Eg: DES • Substitution-Permutation Network (SPN) • Eg: AES
Block Ciphers: Designs • Popular Design Paradigms • Feistel Network Feistel Network • Eg: DES • Long line of work analyzing provable security of Feistel [LR88, Pat03, Pat04] • Security been studied in various security models [Pat10, HR10, HKT11, Tes14, CHKPST16] • Substitution-Permutation Network (SPN) • Substitution-Permutation Network (SPN) • Eg: AES • In contrast, provable security of SPNs not as well-studied
Related Work
Related Work
Substitution-Permutation Network (SPN)
Substitution-Permutation Network (SPN) . . .
Substitution-Permutation Network (SPN) . . .
Substitution-Permutation Network (SPN)
Substitution-Permutation Network (SPN) . . .
Substitution-Permutation Networks Substitution- Permutation step
Security of SPNs
Security of SPNs 14
Security of SPNs 15
Security of SPNs 16
Security of SPNs • Ideal World • Real World 17
Categorizing SPNs Linear function
Categorizing SPNs
Categorizing SPNs Non-linear function
Results: Linear SPNs
Results: Non-linear SPNs
Interpreting our Results
Interpreting our Results
Results
Constructing Non-linear SPNs
Constructing Non-linear SPNs: Blockwise Universal Permutations
Constructing Non-linear SPNs: Blockwise Universal Permutations
Constructing Non-linear SPNs: Blockwise Universal Permutations
Non-linear SPNs via Blockwise Universal Permutations . . .
Non-linear SPNs via Blockwise Universal Permutations . . .
Non-linear SPNs via Blockwise Universal Permutations
Results
Security of 3-round linear SPN
Security of 3-round Linear SPNs
Results
Takeaway
Thank You
Constructing Non-linear SPNs
SPNs: Applications 1-round SPN
Constructing Non-linear SPNs: Blockwise Universal Permutations
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