GMP is not a cryptographic library and using it prevents you from being constant-time, you'll also be very slow. That's for the math. Then you'll have non-eras

GMP is not a cryptographic library and using it prevents you from being constant-time, you'll also be very slow. That's for the math. Then you'll have non-erased secrets in memory. Now for RSA specifically, you'll likely have one or more issues linked to: - padding oracles - falling to fake primes due to using non-hardened Miller-Rabin vs Baillie - Confusion on the various PKCS specs - Bleichenbeicher attacks - anything in the Wycheproof repo or cryptofuzz