Encryption is the process of converting readable data (plaintext) into an unreadable format (ciphertext) to prevent unauthorized access. A key is used to lock (encrypt) and unlock (decrypt) the message. Without the key, the encrypted data remains scrambled and meaningless.
Symmetric Encryption
Symmetric encryption uses a single key for both encryption and decryption. The same secret key must be known and used by both the sender and the receiver.
How It Works:
Sender: Plaintext → Encrypt with Key → Ciphertext
Receiver: Ciphertext → Decrypt with Same Key → PlaintextCommon Algorithms:
DES (Data Encryption Standard)
Developed in the 1970s, DES encrypts data in 64-bit blocks using a 56-bit key. It’s now considered insecure due to its short key length and vulnerability to brute-force attacks.
3DES (Triple DES)
An improvement over DES. It applies DES three times with either two or three different keys. While more secure than DES, it is slower and still not recommended for modern systems.
Blowfish
A fast and flexible block cipher with a key length up to 448 bits. Designed to replace DES, it’s suitable for applications like password protection and file encryption, but has been mostly replaced by AES.
AES (Advanced Encryption Standard)
The current encryption standard, approved by NIST. It supports 128-bit blocks and key sizes of 128, 192, or 256 bits. AES is secure, fast, and widely used in systems like Wi-Fi (WPA2/WPA3), SSL/TLS, and disk encryption.
Asymmetric Encryption
Asymmetric encryption uses two keys: a public key to encrypt data and a private key to decrypt it. The public key is shared openly, while the private key is kept secret.
How It Works:
Encrypt: Plaintext → Public Key → Ciphertext
Decrypt: Ciphertext → Private Key → PlaintextCommon Algorithms:
RSA (Rivest–Shamir–Adleman)
One of the earliest and most widely used asymmetric algorithms. It relies on the difficulty of factoring large prime numbers. Common in secure email, HTTPS (SSL/TLS), and digital signatures.
Diffie-Hellman Key Exchange
Used for securely sharing a symmetric key over an insecure channel. It does not encrypt data directly but allows two parties to establish a shared secret key without revealing it to others.
Elliptic Curve Cryptography (ECC)
Uses the math of elliptic curves to provide the same level of security as RSA but with smaller keys and faster performance. ECC is ideal for mobile devices and applications with limited computing power.
Hybrid Encryption
Hybrid encryption combines asymmetric and symmetric methods. Asymmetric encryption is used to securely exchange a symmetric key, which is then used to encrypt the actual data.
Why It’s Used:
- Asymmetric encryption alone is too slow for large data
- Symmetric encryption alone requires secure key transfer
- Combining both provides the best of both worlds
Example Use:
In TLS/SSL (used in HTTPS websites), the browser and server use asymmetric encryption to agree on a shared symmetric key, which is then used for the session.
Block vs Stream Ciphers
Encryption algorithms also differ in how data is processed: in fixed-size chunks (blocks) or one bit/byte at a time (streams).
| Type | How It Works | Examples |
|---|---|---|
| Block Cipher | Encrypts data in fixed-size blocks | AES, DES, 3DES, Blowfish |
| Stream Cipher | Encrypts data bit-by-bit or byte-by-byte | RC4, Salsa20, ChaCha20 |
Encryption Comparison Table
| Type | Key Usage | Speed | Security | Common Use Cases |
|---|---|---|---|---|
| Symmetric | Same key for both | Fast | Strong (if key is secret) | File encryption, databases |
| Asymmetric | Public/private keys | Slower | Very secure | Email, authentication, SSL |
| Hybrid | Combines both | Balanced | Strong | Secure web sessions, apps |