RSA Message Encryptor & Decryptor (OAEP)
Encrypt with a public key, decrypt with a private key.
About this tool
This tool performs RSA-OAEP encryption with SHA-256, the modern padding scheme that replaced PKCS#1 v1.5 for new designs. Paste a PEM public key (SPKI) to encrypt, or a PKCS#8 private key to decrypt.
RSA encrypts at most a few hundred bytes per operation (key size minus OAEP overhead), so it is used to protect small secrets — session keys, tokens, credentials — rather than large files.
Like everything on encrypt.tools, this runs entirely in your browser — nothing you enter is transmitted or stored.
Frequently asked questions about RSA Encrypt / Decrypt
Why can I only encrypt short messages?+
RSA encrypts at most a few hundred bytes (key size minus OAEP padding overhead). For larger data, real systems encrypt a random AES key with RSA and the data with AES — hybrid encryption.
What padding does this use?+
RSA-OAEP with SHA-256, the modern padding scheme recommended for new designs over the older PKCS#1 v1.5.
Which key encrypts and which decrypts?+
Encrypt with the recipient's public key; only their matching private key can decrypt. That's the essence of public-key cryptography.
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