This tool is 100% client-side. The key pair is produced by the browser’s native crypto.subtle.generateKey, which draws entropy from the operating-system cryptographically secure random generator, and every representation (SPKI PEM, PKCS #8 PEM, JWK and the SHA-256 fingerprint) is computed locally. There is no server, no upload, no CDN in the crypto path and no telemetry. The keys exist only in this browser tab until you copy or download them, and closing the tab discards them. The only optional network use anywhere on the site is consent-gated ads, which never see your keys.

NIST puts the floor at 2048-bit RSA, which provides roughly 112-bit security and is acceptable through about 2030. For keys that must stay secure well beyond that, choose 3072-bit (~128-bit security) or higher; 4096-bit is stronger still but noticeably slower to generate and to use. For most new systems, elliptic-curve keys (ECDSA / Ed25519) give equivalent security with much smaller, faster keys, so consider those too. Whatever you pick, the security also depends on keeping the private key secret and on how the key is stored.

Web Crypto assigns fixed usages to an RSA key, so you generate a pair for one purpose. A signing key gets the usages sign and verify: you sign with the private key and anyone verifies with the public key — RSA-PSS is the modern, randomized, provably secure scheme, while RSASSA-PKCS1-v1_5 is the older deterministic one that is maximally compatible. An encryption key gets encrypt and decrypt: others encrypt to your public key and only your private key decrypts — RSA-OAEP is the recommended padding. RSA can only encrypt small payloads, so real systems usually encrypt a random symmetric key with RSA and the data with AES (hybrid encryption).

The keys here are genuine and generated locally with the platform CSPRNG, which makes the tool great for testing, learning, JWT signing keys and side projects. But a browser tab is not a hardware security module: a compromised device, a malicious extension or a cross-site-scripting flaw could in principle read a key from memory, and the exported PKCS #8 private key is unencrypted. For high-stakes production keys, generate them with your platform’s own tooling (openssl, ssh-keygen) or inside a managed HSM / KMS so the private key is created and stored where it never touches a browser, add a passphrase before storing it, and rotate immediately if it is ever exposed.