1. Introduction
Encryption and decryption are fundamental concepts in cryptography, used to protect sensitive data from unauthorized access. They ensure confidentiality, integrity, and security in digital communication.
- Encryption converts plaintext into unreadable ciphertext using an encryption algorithm and a key.
- Decryption converts the ciphertext back into readable plaintext using a decryption key.
2. What is Encryption?
Definition
Encryption is the process of converting plaintext (readable data) into ciphertext (unreadable format) using a mathematical algorithm and an encryption key.
Purpose of Encryption
✔ Ensures confidentiality by preventing unauthorized access.
✔ Protects data integrity by preventing modification.
✔ Provides secure communication over an insecure network.
How Encryption Works
- Plaintext (original message) is given as input.
- An encryption algorithm processes the plaintext using an encryption key.
- The output is ciphertext, which is unreadable without the correct decryption key.
Example of Encryption
- Plaintext:
"Hello, World!" - Encryption Key:
12345 - Ciphertext:
#@!%^&*(123)(Unreadable format)
3. What is Decryption?
Definition
Decryption is the reverse process of encryption, where ciphertext is converted back into plaintext using a decryption algorithm and a key.
Purpose of Decryption
✔ Restores original data for authorized users.
✔ Allows secure data access and transmission.
✔ Maintains data integrity and authenticity.
How Decryption Works
- Ciphertext (encrypted message) is received.
- A decryption algorithm processes the ciphertext using a decryption key.
- The output is plaintext, which is now readable.
Example of Decryption
- Ciphertext:
#@!%^&*(123) - Decryption Key:
12345 - Decrypted Text (Plaintext):
"Hello, World!"
4. Types of Encryption
Encryption is broadly classified into:
- Symmetric Encryption (Private-Key Encryption)
- Asymmetric Encryption (Public-Key Encryption)
A. Symmetric Encryption (Single Key)
✔ Uses a single key for both encryption and decryption.
✔ Faster and more efficient for large data encryption.
✔ Requires secure key exchange to prevent unauthorized access.
Examples of Symmetric Encryption Algorithms:
| Algorithm | Key Size | Usage |
|---|---|---|
| AES (Advanced Encryption Standard) | 128, 192, 256-bit | Secure file encryption, VPNs |
| DES (Data Encryption Standard) | 56-bit | Legacy encryption, now outdated |
| 3DES (Triple DES) | 168-bit | Secure banking transactions |
| Blowfish | 32-448-bit | Secure passwords, databases |
| RC4 | 40-2048-bit | Wireless encryption (WEP, TLS) |
Example Process of Symmetric Encryption
- Plaintext:
"Secret Message" - Encryption Algorithm: AES
- Key:
"mySecretKey123" - Ciphertext:
"%#@!&12345" - Decryption Algorithm: AES
- Decryption Key:
"mySecretKey123" - Decrypted Text:
"Secret Message"
Limitations: If the key is stolen, the data is compromised.
B. Asymmetric Encryption (Public & Private Key)
✔ Uses two keys – public key for encryption and private key for decryption.
✔ More secure but slower than symmetric encryption.
✔ Used in SSL/TLS, digital signatures, cryptocurrency wallets.
Examples of Asymmetric Encryption Algorithms:
| Algorithm | Key Size | Usage |
|---|---|---|
| RSA (Rivest-Shamir-Adleman) | 1024, 2048, 4096-bit | SSL/TLS, secure email, digital signatures |
| ECC (Elliptic Curve Cryptography) | 160-521-bit | Mobile encryption, cryptocurrency |
| DSA (Digital Signature Algorithm) | 1024-3072-bit | Secure authentication |
| Diffie-Hellman (DH) | 512-4096-bit | Secure key exchange |
Example Process of Asymmetric Encryption
- Plaintext:
"Confidential Data" - Public Key (Encryption Key):
"PublicKey123" - Ciphertext:
"@%$!@&"(Unreadable format) - Private Key (Decryption Key):
"PrivateKey123" - Decrypted Text:
"Confidential Data"
Advantage: Public key can be shared openly; only the private key is kept secret.
5. Comparison: Symmetric vs. Asymmetric Encryption
| Feature | Symmetric Encryption | Asymmetric Encryption |
|---|---|---|
| Keys Used | One shared key | Public & Private key pair |
| Speed | Faster | Slower |
| Security | Less secure (if key is leaked) | More secure |
| Key Distribution | Must be shared securely | Public key can be distributed freely |
| Use Case | Bulk encryption, VPNs | Digital signatures, SSL/TLS |
| Example Algorithms | AES, DES, Blowfish | RSA, ECC, Diffie-Hellman |
6. Real-World Applications of Encryption & Decryption
✔ Secure Websites (HTTPS/SSL/TLS) – Encrypts web traffic to prevent data interception.
✔ Email Encryption (PGP, S/MIME) – Protects emails from unauthorized access.
✔ Cryptocurrency Transactions (Bitcoin, Ethereum) – Uses encryption for secure wallets.
✔ File & Disk Encryption (BitLocker, VeraCrypt) – Secures stored data from theft.
✔ VPNs (Virtual Private Networks) – Encrypts internet traffic for privacy.
✔ Digital Signatures – Used for software authentication, e-contracts, and document verification.
7. Conclusion
Encryption and decryption are essential for cybersecurity, ensuring data privacy, security, and authentication.
- Symmetric encryption is best for fast, large-scale data encryption.
- Asymmetric encryption is ideal for secure communication and authentication.
- Hybrid encryption (combining both) is used in SSL/TLS, VPNs, and secure messaging.
