RSA Decryption
This online tool helps you decrypt messages using RSA. It supports PKCS#1 and OAEP with various hash algorithms. You can also use PEM with a passphrase. Read more
Decrypt RSA ciphertext online
RSA decryption uses a private key to recover a short message encrypted with its corresponding public key. Select PKCS#1 v1.5 or the matching OAEP hash, provide Hex or Base64 ciphertext, and choose how the recovered bytes should be displayed.
The private key may be an unencrypted PEM or a passphrase-protected PEM. Its passphrase unlocks the key container; it is not an RSA padding parameter.
How to decrypt RSA
- Paste the ciphertext and select its input encoding.
- Choose the same padding and OAEP hash used during encryption.
- Paste the private key and enter its PEM passphrase when applicable.
- Decrypt and select the correct output character encoding.
Any mismatch in key, padding, OAEP hash, or ciphertext bytes causes failure. Do not expose detailed decryption failures to untrusted remote users, because distinguishable errors can become a padding oracle.
RSA decryption security
RFC 8017 discusses RSAES-OAEP and the legacy RSAES-PKCS1-v1_5 scheme. New application protocols should use reviewed constructions rather than designing their own RSA message format.
Never paste a production private key into a device or page you do not trust. For long-term or high-value keys, prefer a keystore or hardware-backed operation that prevents key export.
RSA decryption FAQ
Why do I get a decryption error?
Confirm the key pair, ciphertext encoding, padding scheme, OAEP hash, and PEM passphrase. A single changed byte can make the operation fail.
Can this decrypt a large file directly?
No. RSA ciphertext blocks are limited by the modulus; large data normally uses hybrid encryption.
How do I create compatible ciphertext?
Use RSA Encryption with the public key and exactly matching algorithm options.