RSA-OAEP Encrypt & Decrypt Online | PEM PKCS#8 Public Key

This tool provides RSA-OAEP encryption and decryption using the browser's built-in Web Crypto API. RSA-OAEP (Optimal Asymmetric Encryption Padding) is the recommended padding scheme for new applications, replacing the deprecated PKCS#1 v1.5. The tool includes a built-in key generator, key inspector, and PKCS#8/PKCS#1 format conversion. All cryptographic operations run locally — your keys and data never leave your device.

RSA Key Size & Capacity

Maximum plaintext size with SHA-256 OAEP padding (key size − 66 bytes overhead):

Key Size	Max Plaintext	Security Level	Recommended
RSA-2048	190 bytes	112-bit	Minimum acceptable
RSA-3072	318 bytes	128-bit	Recommended for most use
RSA-4096	446 bytes	152-bit	High-security applications

Code Examples

Encrypt and decrypt with RSA-OAEP:

// Browser — Web Crypto API RSA-OAEP
const keyPair = await crypto.subtle.generateKey(
  { name: 'RSA-OAEP', modulusLength: 2048, publicExponent: new Uint8Array([1,0,1]), hash: 'SHA-256' },
  true, ['encrypt', 'decrypt']
);
const ct = await crypto.subtle.encrypt(
  { name: 'RSA-OAEP' }, keyPair.publicKey, new TextEncoder().encode('secret')
);
const pt = await crypto.subtle.decrypt(
  { name: 'RSA-OAEP' }, keyPair.privateKey, ct
);
console.log(new TextDecoder().decode(pt));

# Python — RSA-OAEP with cryptography library
from cryptography.hazmat.primitives.asymmetric import rsa, padding
from cryptography.hazmat.primitives import hashes

key = rsa.generate_private_key(public_exponent=65537, key_size=2048)
ct = key.public_key().encrypt(
    b'secret',
    padding.OAEP(mgf=padding.MGF1(hashes.SHA256()),
                 algorithm=hashes.SHA256(), label=None)
)

Security Notes

• RSA-OAEP only — never use PKCS#1 v1.5 for encryption; it is vulnerable to padding oracle attacks (Bleichenbacher).
• Hybrid encryption for large data — RSA can only encrypt data smaller than key size minus padding; use RSA to wrap an AES key for bulk data.
• Hash must match — the OAEP hash algorithm must be identical between key generation and encryption/decryption.
• Key size ≥ 2048 bits — NIST recommends at least 2048-bit RSA; 3072+ for long-term security.

Related Tools

Need to generate RSA key pairs? The RSA Key Generator creates PEM-formatted keys with configurable parameters. To convert between PKCS#1 and PKCS#8 formats, try the PEM Format Converter. For hybrid encryption workflows, combine with AES Encrypt/Decrypt.