Putting It All Together

You've built every piece:

Modern alternatives to RSA:

• Ed25519 (signatures): 256-bit keys, much faster, smaller signatures (64 bytes vs 256+ for RSA-2048). Used by SSH (default since 2016), Signal, GitHub.
• X25519 (key exchange): the ECDH equivalent. Used by TLS 1.3.
• Kyber (post-quantum): NIST 2024 standardization. Drop-in replacement for RSA key exchange.
• Dilithium (post-quantum signatures): NIST 2024 standard.

When does RSA still make sense?

• Legacy compatibility (old TLS clients)
• Protocols that hardcode RSA (some PKCS#11 tokens, smart cards)
• Long-term archival (RSA-4096 is a known quantity)

For new applications, prefer Ed25519/X25519. RSA's footguns are real, and its algorithms predate modern crypto best practices by decades.

You now understand the most-deployed asymmetric algorithm in history.