RSA Key Generator, Encryption & Signatures

Online RSA tool to generate PEM keypairs (1024, 2048, 4096 bit), encrypt messages, decrypt ciphertexts, sign, and verify signatures.

Deep-Dive Educational Guide

How Public-Key Cryptography Works: The Mathematics of RSA & Prime Factorization

An intuitive breakdown of asymmetric cryptography: trapdoor one-way functions, Euler’s Totient Theorem, modular exponentiation, and how 2048-bit RSA secures HTTPS across the world.

Read Companion Guide →

How to Use RSA Key Generator, Encryption & Signatures

  1. Generate or Paste Keypair: Generate a new 1024, 2048, or 4096-bit RSA PEM keypair or paste an existing private/public key.
  2. Choose Operation Mode: Select Public Key Encryption, Private Key Decryption, Digital Signature Creation, or Signature Verification.
  3. Inspect Output or Signature Status: View the Base64-encoded ciphertext or verify RSA-PSS / PKCS#1 v1.5 signature validity.

Frequently Asked Questions

What is RSA asymmetric cryptography?

RSA is a public-key cryptosystem that relies on the computational difficulty of factoring large composite integers. It enables secure communication without sharing secret keys in advance.

What RSA key size is secure for production use?

NIST recommends a minimum key size of 2048 bits for current applications, with 4096 bits recommended for long-term security archives.

Can RSA be used to encrypt large files directly?

No. RSA can only encrypt plaintexts smaller than its key modulus. In practice, RSA is used in hybrid encryption: encrypting a fast symmetric key (like AES-256) which encrypts the file.