Timed-release cryptography addresses the problem of "sending messages into the future": a message is encrypted so that it can only be decrypted after a certain amount of time, either (a) with the help of a trusted third party time server, or (b) after a party performs the required number of sequential operations. We generalise the latter case to what we call effort-release public key encryption (ER-PKE), where only the party holding the private key corresponding to the public key can decrypt, and only after performing a certain amount of computation which may or may not be parallelisable. Effort-release PKE generalises both the sequential-operation- based timed-release encryption of Rivest, Shamir, and Wagner, and also the encapsulated key escrow techniques of Bellare and Goldwasser. We give a generic construction for ER-PKE based on the use of moderately hard computational problems called puzzles. Our approach extends the KEM/DEM framework for public key encryption by introducing a difficulty notion for KEMs which results in effort-release PKE. When the puzzle used in our generic construction is non-parallelisable, we recover timed-release cryptography, with the addition that only the designated receiver (in the PKE setting) can decrypt. © 2012 Springer-Verlag.
CITATION STYLE
Rangasamy, J., Stebila, D., Boyd, C., Gonzalez-Nieto, J. M., & Kuppusamy, L. (2012). Effort-release public-key encryption from cryptographic puzzles. In Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) (Vol. 7372 LNCS, pp. 194–207). https://doi.org/10.1007/978-3-642-31448-3_15
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