I just completed a major cryptographic project overhauling the security at my company. (Re-doing our password hashing and authentication, and the protocol for a

I just completed a major cryptographic project overhauling the security at my company. (Re-doing our password hashing and authentication, and the protocol for all our networking and communications.) The password hashing was easy: a portable implementation built as a static / shared C library + language bindings linking to OpenSSL's `libcrpyto` for PBKDF2 (with an alternate implementation using CommonCrypto on iOS / OSX). The encryption and authentication layer for the communications was much tricker. The first draft was an implementation based on industry standards: RSA2048 + AES256. It needed to be portable to iOS in addition the various other platforms supported, and Apple has deprecated OpenSSL on iOS and OSX. Annoyingly, OpenSSL does not ship with darwin-arm support out of the box, so a custom compile was not an easy option either. In the end, I ended up picking NaCl, and specifically `libsodium` as a portable implementation. The library, unlike OpenSSL, is beautifully designed and very easy to use, and implements asymmetric crypto functions (based on elliptic curves) which are actually much superior to RSA, providing much greater security for much shorter key length. Libsodium is highly recommended.