Abusalah et al. recently constructed the first constrained PRF for inputs of arbitrary length whose sets $S$ are decided by Turing machines. They use their CPRF to build broadcast encryption and the first ID-based non-interactive key exchange for an unbounded number of users. Their constrained keys are obfuscated circuits and are therefore large.
In this work we drastically reduce the key size and define a constrained key for a Turing machine $M$ as a short signature on $M$. For this, we introduce a new signature primitive with constrained signing keys that let one only sign certain messages, while forging a signature on others is hard even when knowing the coins for key generation.Category / Keywords: secret-key cryptography / Constrained PRFs, unbounded inputs Date: received 12 Mar 2016 Contact author: fuchsbau at di ens fr Available format(s): PDF | BibTeX Citation Version: 20160314:075002 (All versions of this report) Short URL: ia.cr/2016/279 Discussion forum: Show discussion | Start new discussion