Encrypt text with RSA-OAEP

Encrypt a small message with a recipient’s RSA-OAEP public key.

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ToolRSA-OAEP Encrypt
Input
Output
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How it works

The message is label-hashed, OAEP-padded with fresh random seed bytes, and exponentiated with the public key. Repeating encryption of the same message produces different ciphertext when randomness is fresh.

  • Random padding prevents deterministic output.
  • SHA-256 is a common modern digest.

Worked example

RSA Encrypt
Encrypt a message using an RSA public key in JWK format
Input
											Input: utils tools test message
Public key: {"alg":"RSA-OAEP-256","e":"AQAB","ext":true,"key_ops":["encrypt"],"kty":"RSA","n":"1Nga8f8mHyoZglSdI9bHbySgjbdB4h320pIB0Rap6bcMGePIuh3SOfCJBqkYuqK0HMoWDlvPQfbl-kw9rUxXbVa1pxK5WUdMSvFba4Y9AdususV94Ls7M-PjE94NdfQNegjkgWsgjrLljHYZuY8o9VIHGAzn8lsJJzaNWsuVdI2s_Lba3Qws__wq9sl9J3pxahg3xvbt_XIKpU6Xk3kBSRIeE_oT5x2SjxSU_DyzpVvT0OWe0k3-Hc-GMoDxGy79ZtCpIJHlMlYYDJZQOeniD7rgwZC1ePwx_PrUNusTSx3ok5n7VxP7XeLs4pANcipqKhcfp9k3NXnumcbNMH1WpQ"}
Output
												LjIGjPFtZxVQbk3QVWwvnnwh3VB1kBgEZE+4omjWlC+s/qRANxbiw8HCZA8kCTEQhLfO8YaG5L3s12j9EUCzm5wAbqX5DFgZC42jZ4ajTxtCB8/GEaRo6gFtiPa2fJgzxtB5PO3ulQjgxTWVnhacdwgmERJTMm38ZDzdwb6LbW/MT08w6OxTLfL1sqcTE+WqrKaT1lTvBm7EBhSpc1YHNsJbfitVWYmDwWL6KfTNq9SO/A2VOQrq7zaz4+5+lCEgTTWs4A8HyRZF2AIN2cI4s8moRXFHEEQVsZi8/0f6ysAF5VEr0Vhm6LrzPNGfRaMP4F3Hjmm5pixBt4aCMg0egw==

When to use this

Key wrapping, provisioning secrets, and RSA test vectors encrypt small messages.

Edge cases

  • Messages over the OAEP limit cannot fit.
  • Repeated encryption should differ with fresh randomness.
  • Public-key encryption does not authenticate the sender.

References