2000 Fiscal Year Final Research Report Summary
A Study on Traceable Broadcast Encryption Schemes
| Project/Area Number |
11680348
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
計算機科学
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
KAORU Kurosawa Graduate Schoole of Science and Enginnering, Tokyo Institute of Technology, Professor, 大学院・理工学研究科, 教授 (60153409)
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| Project Period (FY) |
1999 – 2000
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| Keywords | Cryptography / Broadcast Encryption / Traitor Tracing / 追跡可能暗号系 |
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| Research Abstract |
In many systems which distribute messages to authorized users over a broadcast channel, a data supplier T gives each authorized user a personal decryption key. However, some malicious authorized users (traitors) may create a pirate key and give it to a pirate (an un-authorized user). A (k, n)-traceability scheme is a scheme in which at least one traitor is detected from a pirate key if there are at most k traitors among n authorized users. Kurosawa and Desmedt found lower bounds on the size of keys and the size of ciphertexts of traceability schemes. They also proposed a scheme which meets these bounds. However, Stinson and Wei showed a linear attack.
This research first presented a proven secure tracing algorithm for the KD scheme. It will trace not only the traitors who use the Stinson-Wei attack but also any traitors.
On the other hand, it is often desirable for the center to be able to exclude certain users from recovering the message that is broadcast in encrypted form. We say that a broadcast encryption scheme is a (c, N)-Broadcast Exclusion Scheme ((c, N )-BEX) if a center can exclude any c or less users among N users. This research next showed that a (c, N)-BEX is obtained from a cover free family. It also showed a new construction of cover free families using almost strongly universal hash function families such that overhead=O(c^2). This scheme has good tracebaility as well.
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