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I'm designing a system where the client asked for documents to be encrypted with "asymmetric cryptography".

I've explained them that the best practice is to encrypt the data with a symmetric algorithm using a randomly generating key and then, using an asymmetric algorithm, to encode that key. The entire scheme is "asymmetric" but it uses multiple algorithms. I offered the usual performance/convenience arguments.

However they are insisting that we should only use asymmetric algorithms because they "have read that is better".

I'm preparing a note for them to better explain the topic and I would greatly benefit of official documents. I browsed the NIST, FIPS, RFC documents and so on but they are too wide to be used as a reference for a customer that is not well versed on this topic.

Does anyone have some pointers to authoritative sources that explain the best practices and that I could use to back up my arguments?

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The PGP, which is well known, uses what is in your mind, hybrid solution. Here a short documentation for your cause.

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  • $\begingroup$ Thanks, I'll surely use it as it gives a very clear explanation. Even if SANS is well known, I was hoping for something even more "official". $\endgroup$ – Remo.D Sep 12 '18 at 8:08
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You're indeed looking for hybrid encryption. Shoup has a lot of papers on hybrid encryption and proposals for KEM/DEM approaches, for example this submission. It describes the motivation and security for such a framework.

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  • $\begingroup$ Thanks. I'll make use of that as well. in the meantime I've found a NIST document: dtic.mil/dtic/tr/fulltext/u2/a389360.pdf that provides guidelines on this aspect. Of course, the more I can add, the better. $\endgroup$ – Remo.D Sep 12 '18 at 9:12

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