Question 1

What is an RSA key pair?

Accepted Answer

An RSA key pair consists of a public key and a private key. The public key encrypts data or verifies signatures and can be shared freely. The private key decrypts data or creates signatures and must be kept secret. RSA is an asymmetric algorithm — what one key locks, only the other can unlock. Key pairs are used in TLS/SSL certificates, SSH authentication, JWT RS256 signatures, and code signing.

Question 2

What RSA key size should I use?

Accepted Answer

Use 2048-bit RSA as a minimum for new applications. 4096-bit provides higher security at the cost of slower operations and larger key/signature sizes. Key sizes below 2048 bits (512, 1024) are considered insecure and should not be used. For very long-lived secrets or high-security requirements, prefer 4096-bit or consider switching to elliptic curve cryptography (ECDSA/Ed25519) which provides equivalent security with much smaller keys.

Question 3

What is PEM format for RSA keys?

Accepted Answer

PEM (Privacy Enhanced Mail) is the most common format for storing RSA keys. A PEM file is Base64-encoded DER data wrapped in a header and footer like '-----BEGIN RSA PRIVATE KEY-----' and '-----END RSA PRIVATE KEY-----'. PEM files are used by OpenSSL, Apache, Nginx, and most cryptographic libraries. The newer PKCS#8 format uses '-----BEGIN PRIVATE KEY-----' and supports multiple key types.

Question 4

Is it safe to generate RSA keys in a browser?

Accepted Answer

Yes — this tool uses the browser's Web Crypto API (crypto.subtle.generateKey) to generate keys, which uses the operating system's cryptographically secure random number generator. The keys are generated entirely in your browser and are never transmitted anywhere. For production use, you can also generate keys locally with OpenSSL: 'openssl genrsa -out private.pem 2048'.

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مولد جفت‌کلید RSA

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کلید عمومی (SPKI PEM)

کلید خصوصی (PKCS#8 PEM)

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