Crypt::RSA without Pari
Crypt::RSA is a module that's been around since 2001, when Vipul Ved Prakash put it on CPAN. It's had only very minor updates since then, and gets used by a few other modules. However, it's had one big problem: it uses Math::Pari for all its calculations, and two of its dependencies (Crypt::Primes and Crypt::Random) also use Pari. Debian in particular has been pining for a version that gets away from the Math::Pari dependency (see RT52689 for some reasons).
I decided to go ahead and do the Pari removal, and it's on CPAN as Alt::Crypt::RSA::BigInt. This uses Ingy's Alt framework -- install the Alt version and you get a new shiny Crypt::RSA. Install the old version and you're back again. There are no Pari dependencies, and if Math::BigInt::GMP is used, it's 5 to 11 times faster. I decided to use Math::BigInt directly, as that makes it very portable, though the speed without either the GMP or Pari backend leaves much to be desired.
This also fixes, to the best of my knowledge, all 11 of the open RT issues with Crypt::RSA, and adds some new features (e.g. SHA256, SHA224, SHA384, SHA512 support, fix Key::Private::SSH, and add new ciphers). It also fixes some serious issues with the key generation caused by Crypt::Primes. I intentionally left the API and internal structure as identical as possible. There's an argument to be made for a new RSA module, but that wasn't the point for this change.
The conversion of the math inside Crypt::RSA was relatively straightforward. The big issues were the dependencies. Math::Prime::Util has fast random prime generation and primality testing, which solves that portion. Fortuitously, David Oswald released Bytes::Random::Secure right before I started on the conversion, and it met all my needs for replacing Crypt::Random.