RSA Encryption/Decryption Tool

RSA (Rivest–Shamir–Adleman) is one of the first and most widely used public-key cryptosystems used for secure data transmission. Unlike symmetric algorithms (like AES) which use a single key, RSA uses a pair of keys: a public key for encryption and a private key for decryption. This asymmetry allows you to share your public key openly while keeping your private key secret.

The security of RSA relies on the practical difficulty of factoring the product of two large prime numbers, the 'factoring problem'. It is a standard for encryption and digital signatures used in SSL/TLS certificates, email encryption (PGP/S/MIME), and secure remote connections (SSH).

Key Features

• <strong>Key Generation</strong>: Create secure 1024, 2048, or 4096-bit RSA key pairs in PEM format.
• <strong>Encryption</strong>: Encrypt messages using a Public Key so only the Private Key holder can read them.
• <strong>Decryption</strong>: Decrypt messages using your Private Key.
• <strong>Digital Signatures</strong>: Sign messages with a Private Key to prove authenticity; anyone with the Public Key can verify it.
• <strong>Padding Modes</strong>: Supports modern <strong>OAEP</strong> (optimal for security) and legacy <strong>PKCS#1 v1.5</strong> (compatibility).
• Multiple hash algorithms: SHA-1, SHA-256, SHA-384, SHA-512
• Padding mode selection: Supports OAEP (recommended) and PKCS#1 v1.5 (legacy compatibility)
• Multiple formats: Input/output supports Text, Base64, Hex and more

Key Size Selection

Choosing the right key size is crucial for security and performance:

• 1024-bit: 1024-bit: Not recommended for new systems, may be cracked within years
• 2048-bit: 2048-bit: Currently recommended minimum, suitable for most applications
• 4096-bit: 4096-bit: Provides highest security, but slower encryption/decryption

Padding Mode

This tool supports two RSA padding modes. Choose based on security requirements and compatibility needs:

• OAEP: Optimal Asymmetric Encryption Padding, provides semantic security and protects against chosen ciphertext attacks. Recommended for new systems.
• PKCS#1 v1.5: Legacy padding mode with known Bleichenbacher attack vulnerability. Only recommended for compatibility with legacy systems.

Format Options

This tool supports multiple data formats for easy integration with different systems:

• Text: Direct UTF-8 text input/output, suitable for regular strings
• Base64: Base64 encoded format, commonly used for network transmission and binary data storage
• Hex: Hexadecimal format, convenient for viewing and debugging binary data

Use Cases

• Secure communication: Encrypt sensitive data before transmission
• Digital signatures: Verify message authenticity and integrity
• Key exchange: Securely exchange symmetric keys
• Identity authentication: Verify sender identity
• Software licensing: Generate and verify licenses

Security Best Practices

• <strong>Key Size</strong>: Use at least 2048-bit keys. 4096-bit is recommended for long-term security. 1024-bit is no longer considered secure.
• <strong>Padding</strong>: Always prefer OAEP (Optimal Asymmetric Encryption Padding) over PKCS#1 v1.5. OAEP prevents 'Padding Oracle' attacks.
• <strong>Key Secrecy</strong>: Never share your Private Key. Anyone with it can read your encrypted messages or impersonate you.
• <strong>Hybrid Encryption</strong>: RSA calculates slowly and has size limits. For large files, use RSA to encrypt a random AES key, then encrypt the file with AES.
• <strong>Client-Side Only</strong>: This tool runs entirely in your browser using the Web Crypto API. Your private keys never leave your device.

Technical Limitations

• <strong>Data Size</strong>: RSA cannot encrypt data larger than its key size minus padding overhead. E.g., 2048-bit RSA with OAEP supports max ~214 bytes.
• <strong>Performance</strong>: RSA is significantly slower than symmetric encryption (AES). Do not use it for bulk data.
• <strong>Format</strong>: This tool uses standard PEM format (Base64 with -----BEGIN... headers). Ensure your other tools support this format.

Technical References

• RFC 8017 - PKCS #1: RSA Cryptography Specifications
• Wikipedia: RSA (cryptosystem)
• NIST SP 800-57: Key Management Guidelines