Decryption
AES, ChaCha20, RSA and other decryption algorithms
Decryption is the process of converting encrypted data (ciphertext) back to original readable data (plaintext). It is the reverse operation of encryption - those with the correct key can decrypt the encrypted data. Modern decryption algorithms are critical for secure communication over the internet, data storage, financial transactions, and protection of personal information.
Use Cases
- Secure internet communication (HTTPS, VPN)
- Data storage and backup
- Email security
- Mobile application security
- Financial transactions
- Cloud storage decryption
- Messaging applications
- Confidentiality
- Data integrity
- Authentication
- Key management
- Performance optimization
| Algorithm | Security | Speed | Use Cases |
|---|---|---|---|
| AES-GCM-256 | Very High | Fast | Disk decryptionVPNSSL/TLSGeneral-purpose decryptionSlightly slower than AES-GCM-128 |
| AES-GCM-128 | Very High | Very Fast | Web applicationsSSL/TLSGeneral-purpose decryption |
| AES-CTR (+HMAC) | For secure use: decrypt-then-MAC, separate keys, unique nonce, and AAD if needed are mandatory. | Very Fast | High-performance applicationsMust be used with HMACDecrypt-then-MAC scheme required |
| ChaCha20-Poly1305 | Very High | Very Fast | Mobile applicationsHigh-performance applications |
| AES-SIV | Very High | Fast | Nonce-misuse resistant applicationsSlower than GCM/ChaCha20-Poly1305 but misuse-resistant |
* Comparisons are relative to reference/hardware acceleration on 64-bit CPU
AEAD (Authenticated Decryption)
Modern algorithms that provide both decryption and authentication. Guarantees both data integrity and confidentiality together.
Symmetric Stream/Block Modes (Unauthenticated)
Modes that provide only decryption. No authentication - must be used together with MAC (HMAC, Poly1305, etc.).
Asymmetric Decryption
Algorithms that use different keys for encryption and decryption. Typically used for key exchange or small data decryption.
Key Unwrap
Algorithms designed for key unwrapping. Should not be used for data decryption - only used to securely unwrap other keys.
Legacy & Insecure
Older decryption algorithms no longer considered secure. Used only for backward compatibility. For 3DES: NIST SP 800-131A - Disapproved for use in applications.
- • FIPS PUB 197
- • NIST SP 800-38A
- • NIST SP 800-38D
- • NIST SP 800-38C
- • RFC 5116
- • RFC 8017
- • NIST SP 800-131A