Question 1

What is RSA and what is it used for?

Accepted Answer

RSA is an asymmetric encryption algorithm that uses a public/private key pair. The public key encrypts data or verifies signatures; the private key decrypts data or creates signatures. It is widely used in TLS/HTTPS, SSH authentication, PGP email, and code signing.

Question 2

What key size should I choose for RSA?

Accepted Answer

2048-bit is the current minimum for new deployments. 4096-bit provides a larger security margin and is recommended for long-lived keys (certificate authorities, archival signing). NIST recommends migrating away from RSA toward elliptic-curve cryptography for future applications.

Question 3

What is the difference between public and private keys?

Accepted Answer

Your public key can be freely shared with anyone. Your private key must be kept secret. In encryption: the sender uses your public key to encrypt; only your private key can decrypt. In signing: you use your private key to sign; anyone with your public key can verify the signature.

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