Networking basics, The Basics of Cryptography

Cryptography is the science of securing information through encoding. It plays a fundamental role in cybersecurity, from encrypting messages to protecting passwords and verifying identities. This tutorial introduces the core principles and types of cryptography.

Step 1: What is Cryptography?

Cryptography transforms data into a form that only authorized parties can understand. It involves two main processes:

  • Encryption: Turning plaintext into unreadable ciphertext.
  • Decryption: Turning ciphertext back into plaintext using a key.

Step 2: Types of Cryptography

  • Symmetric Encryption: Uses the same key for encryption and decryption.
    Examples: AES, DES
  • Asymmetric Encryption: Uses a public key to encrypt and a private key to decrypt.
    Examples: RSA, ECC
  • Hashing: Converts data into a fixed-size string, typically used for data integrity and password storage.
    Examples: SHA-256, bcrypt

Step 3: Symmetric Encryption Example

// Pseudo-code
    encrypted = aes_encrypt("message", key);
    decrypted = aes_decrypt(encrypted, key);

Step 4: Asymmetric Encryption Example

// Pseudo-code
    cipher = rsa_encrypt("secret", public_key);
    plain = rsa_decrypt(cipher, private_key);

Step 5: Hashing Example

hash = sha256("mypassword");

Hashing is one-way; it cannot be reversed. Ideal for storing passwords.

Step 6: Real-World Use Cases

  • HTTPS: Uses asymmetric encryption to exchange symmetric keys securely.
  • Digital Signatures: Verify authenticity using private/public key pairs.
  • JWTs: Use hashing and signing to verify the integrity of tokens.

Step 7: Best Practices

  • Use strong, updated algorithms (e.g., AES-256, RSA 2048+).
  • Never store encryption keys in your source code.
  • Use secure libraries—don't build your own crypto!

Next Steps

Experiment with open-source libraries like OpenSSL or libsodium. Learn about key management, digital certificates, and hybrid encryption schemes for full-stack protection.