RSA Decryption

Decrypt text using RSA-2048 private key

Your private key is only used in your browser and is never sent to the server.

How RSA Decryption Works

RSA decryption uses one of the core principles of asymmetric cryptography: data encrypted with a public key can only be decrypted with the mathematically corresponding private key. This relies on the difficulty of factoring large prime numbers. For RSA-2048, this is practically impossible with current computing power.

Steps to Decrypt RSA

  1. Obtain the encrypted text (ciphertext)
  2. Securely load your private key
  3. RSA algorithm decrypts the ciphertext using the private key
  4. The original text (plaintext) is revealed

Decryption Errors

  • Incorrect Private Key: Private key does not match the public key used for encryption
  • Corrupted Data: Ciphertext may have been corrupted while copying
  • Format Error: Private key must be in correct PEM format
  • Key Size Mismatch: Different key sizes may have been used

Private Key Format

RSA private keys are usually stored in PEM (Privacy Enhanced Mail) format:

-----BEGIN PRIVATE KEY-----
MIIEvQIBADANBgkqhkiG9w0BAQEFAASCBKcwggSjAgEAAoIBAQC...
...
-----END PRIVATE KEY-----

Security Best Practices

  • Never store private keys as plain text
  • Protect private keys with a passphrase if possible
  • Store private keys in a secure password manager
  • Regularly rotate keys
  • Safely destroy old private keys
  • Do not send private keys via email or messaging apps

Use Cases for RSA Decryption

  • Reading encrypted emails (PGP/GPG)
  • Decrypting session keys during SSL/TLS handshake
  • Verifying digital signatures
  • Reading data after secure file transfer
  • Validating license keys

Why Decrypt in the Browser?

This tool performs all decryption operations in your browser using the Web Crypto API. Your private key and decrypted data are never sent to the server. This implements a "zero-knowledge" approach, maximizing privacy. The tool works even without an internet connection.