RSA Encrypt / Decrypt
Free online RSA asymmetric encryption with 1024/2048-bit key generation, PKCS#1/PKCS#8 and OAEP/PKCS1 padding. Runs entirely in your browser.
Runs locally · data never uploaded
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How to use
What it does
RSA is asymmetric: encrypt with the public key, decrypt with the private key — handy for exchanging symmetric keys or signing. This tool generates 1024/2048-bit key pairs locally, imports/exports PEM (PKCS#1 / PKCS#8), and supports OAEP and PKCS#1 v1.5 padding, all in your browser. The private key never leaves your device.
Example
- Click "Generate key pair" to get a public and a private key (2048-bit by default; generation is slow, please wait).
- Pick "Encrypt", type the plaintext and click "Execute" to get Base64 ciphertext.
- Switch to "Decrypt", paste the private key, paste the ciphertext back, then "Execute" to recover the plaintext.
Notes
- Plaintext is capped by the key size: with OAEP on a 2048-bit key the limit is about 190 bytes.
- OAEP is safer; PKCS#1 v1.5 is for legacy interop. Both ends must match.
- Key generation is CPU-heavy; 2048-bit may take from hundreds of ms to a few seconds.
FAQ
Q1.How is RSA different from AES?
RSA is asymmetric with a public/private key pair and is slow, so it suits short data or key exchange. AES is symmetric, fast and good for bulk data. A common pattern is RSA-encrypting the AES key, then AES-encrypting the body.
Q2.Can my keys leak?
No. Key generation and crypto run in your browser; the private key stays on your device and is never uploaded. Avoid "remember params" on shared computers.
Q3.OAEP or PKCS#1 v1.5?
Prefer OAEP — it resists adaptive chosen-ciphertext attacks and is safer. PKCS#1 v1.5 is only for legacy systems. Both ends must use the same padding to interoperate.
Q4.Why does it say the plaintext is too long?
RSA encrypts one block at a time. On a 2048-bit key with OAEP+SHA1 the limit is about 190 bytes. For long text use AES and protect only the AES key with RSA.
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