Cryptology ePrint Archive: Report 1997/012

Self-Delegation with Controlled Propagation - or - What If You Lose Your Laptop.

Oded Goldreich, Birgit Pfitzmann, and Ronald L. Rivest

Abstract: We introduce delegation schemes wherein a user may delegate rights to himself, i.e., to other public keys he owns, but may not safely delegate those rights to others, i.e., to their public keys. In our motivating application, a user has a primary (long-term) key that receives rights, such as access privileges, that may not be delegated to others, yet the user may reasonably wish to delegate these rights to new secondary (short-term) keys he creates to use on his laptop when traveling, to avoid having to store his primary secret key on the vulnerable laptop. We propose several cryptographic schemes, both generic and practical, that allow such self-delegation while providing strong motivation for the user not to delegate rights that he only obtained for personal use to other parties.

Category / Keywords: Delegation, subkeys, key hierarchy, Zero-Knowledge Proofs, Knowledge Complexity, Threshold Schemes, gradual release of secrets, Signature Schemes, Non-Interactive Zero-Knowledge, Commitment Schemes.

Publication Info: Appeared in the THEORY OF CRYPTOGRAPHY LIBRARY and has been included in the ePrint Archive.

Date: Received September 16th, 1997. Revised May 1998. Revised again August 1998.

Contact author: oded at wisdom weizmann ac il

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