The code builds on both my systems - 16.04 and 17.10.

PttnMe, can you tell me what version of OpenSSL you are using on Debian 9 (Sid)? I'm using 1.02g. Were all your errors related to bignum on Debian 9 Sid?

Bitcoin has completely removed bignum and replaced it with a custom class (arith_uint256). I used this whenever possible but couldn't use it for the prime validation code. My first thought was to use GMP, but I ended up staying with bignum so I could use the exact same validation code as in the original. I'm a little concerned now that we might have compatibility problems later on if we stick with bignum. Does anyone have any thoughts on this?