I'm currently building a side project I'd like to release for public use at some point, and I'm using PGP/RSA (soon-to-be ECDSA pending some cross-platform expe

I'm currently building a side project I'd like to release for public use at some point, and I'm using PGP/RSA (soon-to-be ECDSA pending some cross-platform experimentation) for multiple-recipient encrypted messages. What makes ECDSA such a foot-cannon? Caveat: I know enough about encryption to never roll my own.