Encryption, Hashing, Digital Certificate

1. Encryption

• Definition: Encryption is the process of converting readable data (plain text) into an unreadable format (cipher text) to prevent unauthorized access.
• Purpose: Ensures data confidentiality and secures communication.

Types of Encryption

1. Symmetric Encryption:
   • How It Works: Same key is used for both encryption and decryption.
   • Examples:
     • AES (Advanced Encryption Standard): Strong and widely used.
     • DES (Data Encryption Standard): Older, now considered insecure.
     • 3DES: Improvement over DES but slower.
   • Pros: Fast and efficient.
   • Cons: Key management is a challenge (key must be securely shared).
2. Asymmetric Encryption:
   • How It Works: Uses a pair of keys:
     • Public Key: Used for encryption.
     • Private Key: Used for decryption.
   • Examples:
     • RSA: Common for secure communication (e.g., HTTPS).
     • ECC (Elliptic Curve Cryptography): Faster and secure for mobile devices.
   • Pros: Secure key exchange.
   • Cons: Slower than symmetric encryption.

Encryption Algorithms

• AES:
  • Used in WPA2 for securing Wi-Fi networks.
  • Block sizes: 128, 192, or 256 bits.
• RSA:
  • Based on factoring large numbers.
  • Used in SSL/TLS for website security.
• DES/3DES:
  • Block size: 64 bits (DES).
  • 3DES applies DES three times for better security.
• ECC:
  • Efficient for resource-constrained devices.
  • Key size: Much smaller than RSA but equally secure.

Important Features of Encryption

1. Confidentiality: Only authorized users can read the data.
2. Integrity: Ensures data isn’t altered during transmission.
3. Authentication: Verifies the sender’s identity (often paired with hashing).

Common Use Cases

• Data at Rest: Securing files, hard drives, or databases.
  • Example: Full Disk Encryption (FDE).
• Data in Transit: Securing communication over the network.
  • Example: HTTPS, VPNs.
• Applications:
  • Emails (PGP).
  • Secure messaging (WhatsApp uses end-to-end encryption).

Quick Recap Table

Tips to Remember

1. Symmetric Encryption: One key. Think “fast but needs trust.”
2. Asymmetric Encryption: Two keys. Think “secure handshake.”
3. AES > DES: Always choose AES for stronger encryption.

2. Hashing

• Definition: Hashing is a process of converting input data of any size into a fixed-size string of characters, called a hash value or digest.
• Purpose:
  • Ensures data integrity (detects tampering).
  • Provides efficient data retrieval in databases.
  • Secures sensitive data like passwords.

2. Key Features of Hashing

1. Deterministic: Same input always produces the same hash.
2. Fixed Output Size: Regardless of input size, the hash is a fixed length.
   • Example: SHA-256 produces a 256-bit hash.
3. Irreversibility: Hash values cannot be converted back to the original input.
4. Collision Resistance: Two different inputs should not produce the same hash.
5. Fast Computation: Hash functions should be computationally efficient.

3. Popular Hashing Algorithms

1. MD5 (Message Digest 5):
   • Produces a 128-bit hash value.
   • Fast but vulnerable to collisions (not secure for cryptography).
   • Common use: File integrity checks.
2. SHA (Secure Hash Algorithm):
   • SHA-1: 160-bit output. Deprecated due to vulnerabilities.
   • SHA-256: Secure 256-bit output, widely used in cryptography.
   • SHA-512: Stronger version with a 512-bit output.
3. CRC (Cyclic Redundancy Check):
   • Used for error-checking in data transmission, not secure for cryptography.
4. Bcrypt:
   • Specially designed for password hashing.
   • Introduces a salt to prevent attacks like rainbow table.

4. Applications of Hashing

1. Data Integrity:
   • Hashes ensure that data (files, messages) has not been tampered with.
   • Example: Comparing file hashes during downloads.
2. Digital Signatures:
   • Used to verify the authenticity and integrity of messages.
3. Password Storage:
   • Passwords are hashed before storage to ensure security.
   • Example: Login systems.
4. Blockchain:
   • Hashing links blocks together, ensuring immutability.
5. Efficient Searching:
   • Hashing is used in hash tables for fast data retrieval in databases.

5. Differences Between Hashing and Encryption

6. Quick Recap Table

7. Mnemonics for Quick Memory

• SHA: Secure Hash Always – Reliable for security.
• MD5: Mostly Defunct 5 – Avoid for critical uses.
• Hashing Purpose: Think DIP – Data Integrity & Passwords.

3. Digital Certificates

Quick Recap Table

Tips to Remember

1. Encryption: Think of a lock and key (symmetric = 1 key, asymmetric = 2 keys).
2. Hashing: Like a fingerprint—unique and irreversible.
3. Digital Certificates: Like a passport—verifies identity.

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