Certified Everlasting Secure Collusion-

Explore the innovative concept of Certified Deletion in Cryptography, addressing limitations of classical encryption through functional encryption with certified deletion. Delve into the main contributions, technical hurdles, prior works, and more in this cutting-edge field.

• Cryptography
• Security
• Encryption
• Certified Deletion
• Innovation

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Uploaded on Feb 25, 2025 | 0 Views

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1. Some icons from Freepik www.flaticon.com Certified Everlasting Secure Collusion- Resistant Functional Encryption, and More Taiga Hiroka Kyoto University Fuyuki Kitagawa NTT SIL and NTT TQC Tomoyuki Morimae Kyoto University Ryo Nishimaki NTT SIL and TQC Tapas Pal Takashi Yamakawa NTT SIL and NTT TQC KIT

2. Main Contributions Functional encryption with certified deletion Compute-and-compare obfuscation with certified deletion Application to predicate encryption with certified deletion 2

3. What is Cryptography with Certified Deletion?

4. Limitation of Classical Cryptography Can copy classical information as much as you want Keep a copy Store Download Proving deletion is impossible by classical cryptography Certified deletion using quantum power! 4

5. Functional Encryption with Certified Deletion ?? ??? ??????(?): ?????: ?( ) ??? ??? ?? ?????? ???? 5

6. Certified Everlasting Security Deleted! ??? 6

7. Prior Works and Main Question All-or-nothing type encryption with certified deletion SKE, PKE, ABE, FHE, WE, TRE, COM [BI20, HMNY21, HMNY22, Poremba23, BK23, BKP23, AKL23, KNY23, BKMPW23,] Functional encryption with certified deletion? And more other cryptographic primitives? 7

8. Technical Hurdles and Solution

9. Bartusek-Khurana Compiler General compiler for certified deletion ? {SKE, PKE, ABE, FHE, TRE, WE, COM} ? with certified deletion Work for FE? 9

10. Why does BK Compiler not work for FE? Using BB84 state: ??= ????? ?,? 0,1? Enc: ?? ???(?,( ?:??=0??) ?) ?? = (?,?) We get ?(( ?:??=0??) ?) for FE Deletion: Measure ?? in Hadamard basis Measurement result ? = ? Verify: Check ?? = ?? for all ? s.t. ??= 1 10

11. Solution: Public-Slot FE Input: ??? ??? ??? ?( ,???) OWF Public-slot FE FE with certified deletion IO 11

12. Unmask by Public Slot ???: 1-bit case for simplicity |?? ,???(?,?) ? = ?:??=0?? ? ??????(?): ??? ? where ? ? ?,?,??? = ?( ?:??=0???? ?) Use |?? as public input (coherently) Functionality is OK ? can use any public input Security issue ? can obtain ?(1 ?) by using ???? ???? 12

13. Certify BB84 State by One-Time Signature Sig for BB84 state If ??= 0 If ??= 1 ??|??,?? ?? = 0 ??,0 + 1??1 |??,1 Modified ? ? ? ?,?,??,???,? = ?:??=0???? ? private public if ??is valid for ????for all ? s.t. ??= 0 Verify: measure |?? in Hadamard basis outcome (??,??) satisfies ??= ?? ??(??,0 ??,1) 13

14. Proof Intuition Cannot modify the public input part due to unforgeability Forcing ? to use valid computational basis part Cannot get beyond ?(?) and apply the BK lemma Other subtle issues: - bit-by-bit applications of the BK lemma while keeping ? ?0 = ?(?1) redundant encoding - OTS compatible with public slot FE Lamport SIG based on PRG 14

15. Other Constructions with Certified Deletion Bounded collusion-resistant FE from PKE Garbled circuits and receiver non-committing encryption with certified deletion 1 Compute-and-compare obfuscation from LWE 2 Predicate encryption from LWE Attribute-hiding is non-trivial even though PE is all-or-nothing type 3 15

16. Wrap-up

17. Beyond All-or-Nothing Type Encryption FE with certified deletion & many other interesting cryptographic primitives ia.cr/2023/236 Thank you! Concurrent and independent work (yesterday s talk): Bartusek-Goyal-Khurana-Malavolta-Raizes-Roberts also achieve FE with certified deletion using a different approach 17