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I am implementing Role-based access control by referencing the paper Enforcing Role-Based Access Control for Secure Data Storage in the Cloud. In page 6, they have mentioned to choose hash functions $H_1$ and $H_2$ during the setup

$$H1 : \{0, 1\}^∗ \rightarrow Z^∗_p,$$ $$H2 : G_T \rightarrow Z^∗_p$$ where $G_T$ be a cyclic multiplicative group.

Can anyone please explain me the notation of the two hash functions? Should the two hash functions $H_1$ and $H_2$ be implemented using different cryptographic hash algorithms? or can I use $\operatorname{SHA-256}$ (for example) to implement both of them? If No, please recommend me cryptographic hash algorithms for them.


marked as duplicate by Maarten Bodewes, otus, SEJPM, yyyyyyy, CodesInChaos Jun 27 '16 at 15:07

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migrated from security.stackexchange.com Jun 26 '16 at 20:49

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    $\begingroup$ Voted to migrate to cryptoSE $\endgroup$ – wireghoul Jun 26 '16 at 11:31