Encryption: full-disk, file, volume, database, transport, symmetric/asymmetric, key length, key exchange, algorithms

1.4 Cryptographic solutions

📘CompTIA Security+ SY0-701

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1. What is Encryption?

Encryption is the process of scrambling data so that only authorized people or systems can read it.

• Plaintext: The original readable data.
• Ciphertext: The scrambled, unreadable version of data.
• Decryption: Converting ciphertext back into readable plaintext.

Why it matters in IT: Encryption keeps data safe from hackers, unauthorized users, and eavesdroppers.

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2. Types of Encryption in IT Systems

Encryption can be applied at different levels depending on what you need to protect:

A. Full-Disk Encryption (FDE)

• Encrypts the entire hard drive, including the operating system, applications, and files.
• Example in IT: BitLocker (Windows) or FileVault (Mac) encrypts the whole disk so that if the device is stolen, the data cannot be accessed without the key.

B. File-Level Encryption

• Encrypts specific files instead of the entire disk.
• Example: Encrypting a spreadsheet with sensitive data before sharing over the network.

C. Volume Encryption

• Encrypts specific storage volumes or partitions, not the full disk.
• Example: LUKS (Linux) encrypts only a partition that stores customer information.

D. Database Encryption

• Encrypts specific database content (like personal information or payment data).
• Example: MySQL or Oracle encrypting credit card numbers in database columns.

E. Transport Encryption

• Encrypts data moving across a network to prevent eavesdropping.
• Example: HTTPS uses TLS/SSL to encrypt communication between a web browser and a server.

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3. Encryption Methods

There are two main methods:

A. Symmetric Encryption

• Uses one key for both encryption and decryption.
• Pros: Very fast, good for large amounts of data.
• Cons: Sharing the key securely is a challenge.
• Common Algorithms:
  • AES (Advanced Encryption Standard) – widely used, strong
  • DES/3DES – older, mostly phased out
  • RC4 – legacy

IT Example: Encrypting files on a server using AES, with the same key used to decrypt the files later.

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B. Asymmetric Encryption

• Uses two keys: a public key (anyone can use to encrypt) and a private key (only the owner can decrypt).
• Pros: No need to share the private key; ideal for secure communication.
• Cons: Slower; usually used for small data (like encrypting keys).
• Common Algorithms:
  • RSA – used in SSL/TLS certificates
  • ECC (Elliptic Curve Cryptography) – strong encryption with smaller keys
  • Diffie-Hellman – used for secure key exchange

IT Example: HTTPS websites use RSA or ECC to exchange a session key securely, then switch to fast symmetric encryption for the actual data transfer.

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4. Key Length

• Longer keys = stronger encryption, harder to break.
• Common lengths:
  • AES: 128, 192, 256 bits
  • RSA: 2048, 3072, 4096 bits

Exam Tip: Remember – longer key = stronger security, slightly slower performance.

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5. Key Exchange

• Key exchange is how systems share encryption keys securely.
• Especially important for symmetric encryption, because both sides need the same key.
• Common methods:
  • Diffie-Hellman: Two systems create a shared key without sending it directly.
  • Public Key Infrastructure (PKI): Uses asymmetric encryption to share symmetric keys securely.

IT Example: Browser and server use asymmetric encryption to share a symmetric key, then use the symmetric key for faster encryption during the session.

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6. Common Encryption Algorithms

Type	Examples	Use Case
Symmetric	AES, DES, 3DES	Fast encryption of files, disks, databases
Asymmetric	RSA, ECC, DH	Key exchange, digital signatures
Hashing (related)	SHA-2, SHA-3	Data integrity, password storage

Tip for the exam:

• Symmetric = same key for encrypt/decrypt
• Asymmetric = public/private keys

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7. How Encryption Works in IT Together

• Scenario: Secure web communication
  1. Browser connects to website using HTTPS.
  2. Website sends public key (asymmetric).
  3. Browser generates session key (symmetric) and encrypts it with public key.
  4. Server decrypts session key with private key.
  5. Both sides now use symmetric key (AES) for fast encryption.

This is hybrid encryption: asymmetric for key exchange, symmetric for speed.

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✅ Key Points for the Exam

1. Symmetric = fast, one key; Asymmetric = slower, public/private keys.
2. Key length affects strength: longer = stronger.
3. Encryption levels: full-disk, file, volume, database, transport.
4. Key exchange ensures secure sharing of symmetric keys.
5. Common algorithms: AES, DES/3DES (symmetric), RSA, ECC (asymmetric), Diffie-Hellman (key exchange)

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