TY - GEN

T1 - Obfuscating point functions with multibit output

AU - Canetti, Ran

AU - Dakdouk, Ronny Ramzi

N1 - Funding Information:
Work supported by NSF grants 0331548 and CFF-0635297, and BSF grant 2006317.

PY - 2008

Y1 - 2008

N2 - We construct obfuscators of point functions with multibit output and other related functions. A point function with multibit output returns a fixed string on a single input point and zero everywhere else. Obfuscation of such functions has a useful application as a strong form of symmetric encryption which guarantees security even when the key has very low entropy: Essentially, learning information about the plaintext is paramount to finding the key via exhaustive search on the key space. Although the constructions appear to be simple and modular, their analysis turns out to be quite intricate. In particular, we uncover some weaknesses in the current definitions of obfuscation. One weakness is that current definitions do not guarantee security even under very weak forms of composition. We thus define a notion of obfuscation that is preserved under an appropriate composition operation. The constructions can use any obfuscator of point functions under the proposed definition. Alternatively, they can use perfect one way (POW) functions with statistical indistinguishability, or with computational indistinguishability at the price of somewhat weaker security.

AB - We construct obfuscators of point functions with multibit output and other related functions. A point function with multibit output returns a fixed string on a single input point and zero everywhere else. Obfuscation of such functions has a useful application as a strong form of symmetric encryption which guarantees security even when the key has very low entropy: Essentially, learning information about the plaintext is paramount to finding the key via exhaustive search on the key space. Although the constructions appear to be simple and modular, their analysis turns out to be quite intricate. In particular, we uncover some weaknesses in the current definitions of obfuscation. One weakness is that current definitions do not guarantee security even under very weak forms of composition. We thus define a notion of obfuscation that is preserved under an appropriate composition operation. The constructions can use any obfuscator of point functions under the proposed definition. Alternatively, they can use perfect one way (POW) functions with statistical indistinguishability, or with computational indistinguishability at the price of somewhat weaker security.

KW - Composable obfuscation

KW - Digital locker

KW - Multibit point function obfuscation

KW - Obfuscation

KW - Point function obfuscation

UR - http://www.scopus.com/inward/record.url?scp=44449095554&partnerID=8YFLogxK

U2 - 10.1007/978-3-540-78967-3_28

DO - 10.1007/978-3-540-78967-3_28

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AN - SCOPUS:44449095554

SN - 3540789669

SN - 9783540789666

T3 - Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)

SP - 489

EP - 508

BT - Advances in Cryptology - EUROCRYPT 2008 - 27th Annual International Conference on the Theory and Applications of Cryptographic Techniques, Proceedings

Y2 - 13 April 2008 through 17 April 2008

ER -