Work around build break

[linas]

The source code does not build under Ubuntu 16.04 (Xenial) - these changes are needed for make forward progress.

I note that the files in the cryptopp directory appear to mirror the files installed by the libcrypto++-dev package. This makes me nervous from the security standpoint: if there any bug-fixes to libcrypto++-dev, the BitcoinArmory will not benefit from them. Also, copying source code like this just makes the whole package harder to audit. Copying source is usually considered to be an emergency measure, when the copied package is out-of-date or unmaintained, which does not seem to be the case for libcrypto++-dev. So this is a confusing situation.

[achow101]

The source code is copied in order to allow for static linking. IIRC there were a few custom changes to it.

[linas]

Hmm. OK. The "few custom changes" should be fed upstream, where they can be audited and controlled by the package maintainers.

[goatpig]

CryptoPP was unmaintained when Armory and Core were built around it. Wei Dai eventually resumed development sometimes in 2016. I'll be moving to Core's own crypto lib through libbtc so I do not intent to do anything about CryptoPP besides dumping it.

[droark]

@linas - Crypto++ has some custom modifications so that Armory can support RFC 6979. It was submitted upstream and eventually accepted in a modified form. (Same results, slightly more robust code.) However, it won't be released until at least v5.7 (or v6.0???). For now, Armory has to use modified code. I don't know offhand if Core's libraries include 6979 support. If they do, then yeah, Crypto++ needs to go away. (Jeff, the current maintainer, is a nice guy who does have access to Wei's ear and a strong desire to clean up the code. Alas, there's just too much cruft, IMO. That and it's a nightmare to understand some of that code.)

[goatpig]

libbtc (which uses libsecp256k1 under the hood) has RFC 6979. I'm looking the replace CryptopPP with libbtc wholesale.