100% Client-Side

RSA Encrypt & Decrypt

Free online RSA encryption and decryption tool. Encrypt messages with RSA public keys and decrypt with private keys directly in your browser. — runs 100% in your browser, client-side only. No data is sent to any server. Free to use, no account required.

Free Client-Side No Login No Storage
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How to Use the RSA Encrypt & Decrypt

  1. Encrypt: Paste an RSA public key (PEM) and plaintext, then click Encrypt.
  2. Decrypt: Paste an RSA private key (PEM) and the Base64 ciphertext, then click Decrypt.

RSA encryption uses the Web Crypto API (RSA-OAEP with SHA-256). Maximum message size depends on key size (e.g., ~190 bytes for 2048-bit keys). Generate key pairs using the RSA Key Generator tool.

What is RSA Encrypt & Decrypt?

RSA encryption/decryption performs asymmetric cryptography using public/private key pairs. Public keys encrypt data that only the corresponding private key can decrypt, enabling secure communication without shared secrets.

Why Use This Tool

RSA enables secure communication with anyone who has your public key, without pre-sharing secrets. It's fundamental to HTTPS, SSH, PGP, and most secure communication systems.

When to Use It

Use RSA encryption when sending secret data to someone whose public key you have, testing asymmetric encryption implementations, or learning public-key cryptography.

Who Should Use It

Security engineers, backend developers, compliance teams, and learners implementing key-based encryption workflows.

How to Use the RSA Encrypt & Decrypt

  1. Generate or import RSA public/private key pair.
  2. Encrypt short plaintext or a symmetric session key with the public key.
  3. Decrypt using matching private key.
  4. For larger payloads, use hybrid encryption (AES for data + RSA for key).

Security note

Use modern padding (OAEP) and at least 2048-bit keys. Avoid raw RSA and never expose private keys in client logs or analytics.

Common Uses

  • Testing RSA implementations
  • Learning public-key cryptography
  • Encrypting data for specific recipients

Frequently Asked Questions

What key size should I use?

2048 bits minimum, 4096 recommended for sensitive data. Larger keys are more secure but slower. 1024-bit keys are considered insecure.

Can I encrypt large data?

RSA can only encrypt data smaller than the key size. For large data, encrypt with a symmetric key (AES), then encrypt that key with RSA. This is hybrid encryption.

Is this safe in a browser?

Yes. CipherKit uses Web Crypto API for RSA operations. Your private key never leaves your browser.