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RSA Encryption and Decryption
Tool Description
RSA Encryption and Decryption is an online RSA asymmetric encryption/decryption tool that is free and requires no installation — just open the page to use it. It supports key pair generation (1024/2048/4096-bit), public-key encryption / private-key decryption, private-key signing / public-key verification, and Base64 / Hex output encodings, with RSA + SHA-256 for signing. All operations run locally in your browser — keys and data never leave your device.
How to Use
- Generate Key Pair
Click "Generate Key Pair" to create RSA public and private keys, or manually paste existing keys (PEM format).
- Select Operation Mode
Select the operation mode: Encrypt (public key), Decrypt (private key), Sign (private key), Verify (public key).
- Set Parameters
Choose the key size and output encoding (Base64 / Hex).
- Enter Text
Enter text in the input area (plaintext for encrypt, ciphertext for decrypt, original text for sign).
- Run Operation
Click the action button to execute. The result appears in the output area — copy or download as needed. For verification, the input must contain both the original text and the signature.
Use Cases
- Data Transmission Encryption: Encrypt sensitive data with the recipient's public key — only the holder of the corresponding private key can decrypt it
- Digital Signatures: Sign documents or messages with a private key; the recipient verifies with the public key to ensure data integrity and authenticity
- Key Exchange: In symmetric encryption scenarios, use RSA to securely transmit symmetric keys (e.g. AES keys) for hybrid encryption
- Identity Authentication: In protocols like SSH and HTTPS, RSA key pairs are used for authentication and secure connection establishment
Key Advantages
- Free & No Install
The tool is completely free and works in the browser — no client software to download or install.
- Local & Private
All encryption/decryption and signing/verification run locally in your browser; keys and data never leave your device.
- Full-Featured
Supports key generation, encryption/decryption, and signing/verification — covering common asymmetric crypto needs.
- Multiple Key Sizes
Offers 1024/2048/4096-bit key sizes, balancing compatibility and security.
- Multiple Encodings
Provides Base64 and Hex output encodings for flexible transmission and storage.
- Easy to Use
Clear form parameters with one-click copy and download — no cryptography background needed.
Key Size Comparison
Different key sizes determine the balance between security and performance:
| Key Size | Security Level | Generation Speed | Use Case |
|---|---|---|---|
| 1024-bit | Low, breakable | Fast | Testing and learning |
| 2048-bit | High, recommended | Medium | Most applications |
| 4096-bit | Very high | Slow | High-security scenarios |
Encryption vs Signing
RSA's four operation modes have fundamental differences — please confirm which operation you need:
- Public-Key Encryption - Encrypt data with the public key; only the private key holder can decrypt — ensures confidentiality
- Private-Key Decryption - Decrypt data with the private key to recover the original content
- Private-Key Signing - Generate a digital signature with the private key to prove data origin and integrity
- Public-Key Verification - Verify with the public key that a signature was created by the corresponding private key — confirms data has not been tampered with
FAQ
RSA is an asymmetric encryption algorithm using a public/private key pair — it is slower but ideal for key exchange and signing. AES/DES are symmetric encryption algorithms using the same key for both encryption and decryption — they are fast and suitable for bulk data encryption. In practice, the two are often combined: use RSA to encrypt a symmetric key, then use the symmetric algorithm for the actual data (hybrid encryption).
RSA encryption length is limited by the key size. With PKCS#1 v1.5 padding, the maximum encryption length is (key bits / 8 - 11) bytes. For example, a 2048-bit key can encrypt at most 245 bytes. For longer data, hybrid encryption is recommended: generate a random AES key to encrypt the data, then encrypt the AES key with the RSA public key.
RSA keys are Base64-encoded PEM format text containing the key's mathematical parameters (modulus n, exponent e/d, etc.). The longer the key size, the longer the resulting text. A 2048-bit private key is typically around 1700 characters — this is normal.
Encryption protects data confidentiality (others cannot read it) — encrypt with the recipient's public key, decrypt with the recipient's private key. Signing ensures data integrity and authenticity (proving who sent it and that it was not modified) — sign with the sender's private key, verify with the sender's public key. They serve different purposes; choose based on your needs.
No. All operations (key generation, encryption/decryption, signing/verification) run entirely in your browser. Your keys and data never leave your device.
Possible causes: ① The public key used for verification does not match the private key used for signing; ② The original text has been modified (including spaces and line breaks); ③ The signature format is incorrect (encoding mismatch); ④ The input format is wrong (for verification, the original text and signature must be in the correct format). Make sure you are using the correct public key and the complete original text.
RSA's single-pass encryption length is limited by the key size, so it is not suited to encrypting large files directly. For large files use hybrid encryption: encrypt the file with a symmetric algorithm like AES, then encrypt the AES key with the RSA public key and transmit both.
Yes, and it should be. The public key is used for encryption and verification and is designed to be distributed openly; only the private key must be kept strictly secret — rotate the key pair immediately if it is ever exposed.
No. Key generation runs entirely in your browser — it needs no network and uploads nothing, so you can use it with confidence.
Yes. Text is processed as UTF-8, so Chinese, Japanese, Korean, and any Unicode characters encrypt, decrypt, and sign normally. Output uses Base64 or Hex encoding for safe transmission.
RSA with a 2048-bit or larger key is still considered secure and is widely used in HTTPS, SSH, and more. 1024-bit RSA is considered breakable and should not be used in production; for higher security needs, choose 4096-bit.
Local processing means your private key and data are never uploaded to any server, eliminating leakage risks in transit and storage. It also works offline with faster response and stronger privacy.
Content last updated：2026-07-15
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