What is RSA?
RSA decryption uses your private key to recover data that was encrypted with your matching public key. The same padding scheme (OAEP or PKCS#1 v1.5) used during encryption must be selected. Keep your private key secret — anyone with it can decrypt your messages. Decryption runs entirely in your browser, so your key never leaves your device.
Keep it secret: decryption needs your private key and the same padding used to encrypt. Runs locally in your browser.
How RSA works
RSA decryption is modular exponentiation with the private key:
- The ciphertext is raised to the private exponent d, modulo n.
- The padding (OAEP or PKCS#1 v1.5) is removed.
- The original message is recovered.
How to use
- Paste the RSA ciphertext.
- Enter the same key and settings used to encrypt.
- The decrypted text appears in the output.
Options explained
- Private key — Paste your RSA private key (PEM).
- Padding — Must match the padding used to encrypt (OAEP or PKCS#1 v1.5).
Common uses
- Decrypting secrets sent to you.
- Recovering an encrypted symmetric key in hybrid encryption.
- Secure messaging.
Frequently asked questions
Why does decryption fail?
The wrong private key or a padding mismatch with the encryption step.
Is my private key uploaded?
No. Decryption happens entirely in your browser.
How do I encrypt instead?
Use the RSA Encryption tool with the recipient's public key.