RSA vs ECDSA: Key Size, Performance, Security
How RSA and ECDSA differ in security, key size, performance, and modern adoption — and why ECDSA is preferred for new systems.
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Tags: security, cryptography, signatures
RSA vs ECDSA: Key Size, Speed, and Security Comparison When generating TLS certificates, SSH keys, or JWT signing keys, you choose between RSA and ECDSA (or Ed25519, a modern variant). The choice affects key size, operation speed, certificate size, and long-term security assumptions. Understanding the trade-offs helps you make the right call for each use case. The Mathematics Behind Each RSA (Rivest-Shamir-Adleman, 1977) is based on the difficulty of factoring large semiprime integers. Given a number N = p × q where p and q are large primes, finding p and q from N alone is computationally infeasible at sufficient key sizes. ECDSA (Elliptic Curve Digital Signature Algorithm) is based on the Elliptic Curve Discrete Logarithm Problem (ECDLP). Given a point Q = k × G on an elliptic curve…
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