Encryption, Hashing, Digital Certificate

1. Encryption

Encryption is the process of converting readable data (plain text) into an unreadable format (cipher text) to prevent unauthorized access. The Purpose is to ensure data confidentiality and secure communication.

Types of Encryption

1. Symmetric Encryption:

How It Works: The 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).

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

1. AES:

• AES stands for Advanced Encryption Standard. It’s a very popular and widely used symmetric encryption algorithm.
• Remember how symmetric encryption uses the same secret key for both locking (encrypting) and unlocking (decrypting) a message? AES works exactly like that!
• Key Characteristics of AES:
  • Symmetric: It uses a single, shared secret key for both encryption and decryption.
  • Block Cipher: It encrypts data in fixed-size blocks (128 bits).
  • Highly Secure: It’s considered extremely secure and is used by governments and organisations worldwide to protect sensitive data.
  • Fast and Efficient: It’s designed to be efficient in both software and hardware.
  • Key Sizes: AES can use different key sizes: 128-bit, 192-bit, or 256-bit. A larger key size provides more security, but it also requires slightly more processing time.
  • Used in WPA2 for securing Wi-Fi networks.

2. RSA:

RSA stands for Rivest-Shamir-Adleman, named after its creators. It is the most widely used asymmetric encryption algorithm.

As we discussed with asymmetric encryption, RSA relies on having a pair of mathematically linked keys: a public key and a private key.

How RSA Works (Simply):

The security of RSA is based on the mathematical difficulty of factoring very large numbers.

1. Key Generation:
   • You generate two very large prime numbers (let’s call them p and q). These are kept secret.
   • From these, you calculate two keys:
     • Public Key: This key is made public. Anyone can use it to encrypt a message for you.
     • Private Key: This key is kept absolutely secret by you. Only you can use it to decrypt messages that were encrypted with your public key.
2. Encryption:
   • If someone wants to send you a secret message, they get your publicly available RSA public key.
   • They use your public key to encrypt the message.
   • The encrypted message (ciphertext) is then sent to you.
3. Decryption:
   • You receive the encrypted message.
   • You use your secret private key to decrypt the message back into its original, readable form.

Why it’s “Asymmetric”: The key used to encrypt (public key) is different from the key used to decrypt (private key). Even if someone has your public key, they cannot figure out your private key to decrypt messages.

Uses of RSA:

• Secure communication (e.g., establishing secure connections for websites using HTTPS/TLS)
• Digital Signatures (to verify the authenticity and integrity of a message or document)
• Secure key exchange (to securely share a symmetric key that can then be used for faster, bulk data encryption with algorithms like AES).

• Based on factoring large numbers.
• Used in SSL/TLS for website security.

3. DES/3DES:

DES (Data Encryption Standard)

• What it is: DES was an influential symmetric-key algorithm for encrypting digital data, standardised in 1977. It was widely used for many years.
• How it works (Simply):
  • DES takes a block of plaintext (fixed size, 64 bits) and a secret key (56 bits effective length).
  • It puts the plaintext through a series of complex transformations (substitutions and permutations) over 16 “rounds,” mixing it with bits from the secret key in a specific way.
  • The result is a 64-bit block of ciphertext.
  • To decrypt, the same key is used, and the process is essentially reversed.
• Security: Due to its relatively short 56-bit key length, DES is no longer considered secure against modern attacks (brute-force attacks can crack it in a reasonable amount of time). It’s primarily used in legacy systems or for educational purposes today.

3DES (Triple DES or Triple Data Encryption Algorithm)

• What it is: 3DES was developed as an enhancement to DES to address its security weakness (the short key length). It significantly increases the effective key length and thus the security.
• How it works (Simply): Instead of encrypting a block once, 3DES applies the DES algorithm three times to each data block. There are a few common “keying options,” but the most common and strongest one uses three different keys (K1, K2, K3).
  • Encryption Process (EEE or EDE):
    1. Encrypt the plaintext block with Key 1 (K1) using DES.
    2. Decrypt the result with Key 2 (K2) using DES. (This “decrypt” step might seem counter-intuitive, but it’s part of the standard design, particularly for backward compatibility and enhanced security against certain attacks).
    3. Encrypt the new result with Key 3 (K3) using DES. The output is the final ciphertext.
  • Decryption Process: To decrypt, you reverse the order of operations and keys:
    1. Decrypt with Key 3 (K3).
    2. Encrypt with Key 2 (K2).
    3. Decrypt with Key 1 (K1).
• Security: 3DES is much more secure than single DES, typically offering an effective key length of 112 bits (when using two different keys and the third being a repeat of the first) or 168 bits (when using three truly independent keys). While still used in some older financial systems, it is slower than modern algorithms like AES and is gradually being phased out in favor of AES.

4. ECC:

ECC is a type of asymmetric (public-key) cryptography, just like RSA. However, instead of relying on the difficulty of factoring large numbers (like RSA), ECC’s security is based on the mathematics of elliptic curves over finite fields.

Don’t worry too much about the complex math of elliptic curves. The key takeaway is:

• It allows for the same level of security with significantly smaller keys compared to RSA. This is its biggest advantage!
• It’s more efficient: Smaller keys mean faster computations, less processing power, and less bandwidth needed, making it ideal for mobile devices, IoT, and high-volume web traffic (like HTTPS).

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.

• X
• Instagram
• WhatsApp