Last updated: April 12, 2026
RSA vs ECDSA — Which Cryptographic Signature in 2026?
Quick Answer
RSA uses large prime factorization with 2048-4096 bit keys. ECDSA uses elliptic curve cryptography with much smaller keys (256-384 bits) for equivalent security. ECDSA is faster and uses less bandwidth. Modern systems prefer ECDSA or EdDSA (Ed25519).
RSA vs ECDSA — Side by Side
| Feature | RSA | ECDSA |
|---|---|---|
| Key Size (128-bit security) | 3072 bits | 256 bits |
| Signature Size | 384 bytes (3072-bit key) | 64 bytes (P-256) |
| Sign Speed | Slower | Faster |
| Verify Speed | Faster (for small messages) | Slightly slower |
| TLS Usage | Still common, declining | Preferred in modern TLS |
| SSH Keys | ssh-rsa (legacy default) | Ed25519 (recommended, EdDSA variant) |
| Quantum Resistance | Broken by Shor's algorithm | Broken by Shor's algorithm |
Verdict
Use ECDSA (P-256) or EdDSA (Ed25519) for new systems — smaller keys, faster operations, less bandwidth. RSA is still acceptable at 2048+ bits. For SSH, use Ed25519. Neither is quantum-resistant.
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