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Cryptography Basics

Updated Jan 30, 2024 ·

Cryptography​

The science and practice of securing communication and information through encoding, ensuring only authorized parties can access it. Its purpose is to protect data integrity, confidentiality, and authenticity.

  • Encryption

    • Transforming plaintext into ciphertext using an algorithm and a key.

  • Decryption

    • Converting ciphertext back to plaintext with the appropriate key.

Obfuscation​

Data Masking or Obfuscation​

Obfuscation is a technique to make code, data, or communications harder to understand or analyze.

  • Protect intellectual property, sensitive information.
  • Protect sensitive data from being easily understood or extracted.
  • Prevent unauthorized reverse engineering or tampering with software.

How It Works

  • Code or data is transformed into a form that is functionally equivalent but difficult for humans to read or interpret.
  • Common methods include:
    • renaming variables and functions with meaningless names
    • removing comments
    • reordering code structures.

Considerations

  • Obfuscation is not foolproof.
  • Skilled attackers can often reverse-engineer obfuscated code.
  • Over-obfuscation can complicate legitimate debugging and maintenance.
  • Not a replacement for proper encryption and other security practices.

Steganography​

Steganography and obfuscation are techniques used to conceal information, but they differ in their methods and objectives.

  • Steganography hides a message within another medium to keep its existence secret.
  • Obfuscation makes code or information difficult to understand

Derived from Greek word, meaning "covered writing", Steganography hides secret data within ordinary, non-secret files or messages. Its purpose is not to prevent unauthorized access, but to avoid suspicions.

We can try this at Steganography Online.. We'll use the sample photo below:

The message that we want to hide in the image:

All right men, commence Operation: Special Delivery!

Upload the photo and enter the message in the field. Click Encode.

It will generate the encoded image.

Right-click on the third image > Save as. Then check the properties of the original photo and the encoded photo. We can see that the size changed.

Tokenization​

Tokenization replaces sensitive information with non-sensitive tokens, enhancing data security by removing direct exposure to confidential data.

How It Works

  • Sensitive data is swapped for unique tokens stored in a secure token vault.
  • The original data is stored somewehere.
  • The original data can only be retrieved through secure processes with proper access.
  • If data breach occurs, attackers will only find the useless tokens.

Applications

  • Used in payment systems for credit card security.
  • Applied in healthcare to protect patient information.
  • Employed in databases to secure sensitive data.
  • Supports compliance with data protection regulations.

Considerations

  • The token vault must be securely protected.
  • Tokenization should be part of a comprehensive security strategy.

Diffusion​

Diffusion spreads the effect of a single input across many output elements, thus obscuring patterns.

  • Makes the information less visible, less obvious.
  • In block ciphers, diffusion is achieved through operations like permutations and mixing.
  • Example is blurring an image.

Confusion​

Confusion creates complex relationships between the key and ciphertext, making it difficult to infer the key.

  • Changing a property of the data and make it more difficult to interpret, more unintelligible.
  • Confusion works alongside diffusion to create robust encryption schemes.
  • Example is scrambling or changing the pixels of an image.

Types of Encryption​

These types of encryption play critical roles in modern cybersecurity, often used together to achieve a balance of speed and security.

Symmetric Encryption​

Symmetric cryptography uses the same key for both encryption and decryption. The sender and receiver must share this key, keeping it secret from others.

  • Session key - single key is used to encrypt and decrypt data.
  • Both parties must have this key.

Symmetric encryption is generally faster and less computationally intensive compared to asymmetric cryptography. It is also effective for encrypting large volumes of data.

For more information, please see Symmetric Encryption.

Asymmetric Encryption​

Asymmetric cryptography uses a pair of keys:

  • a public key for encryption
  • a private key for decryption.

The public key can be shared openly, but the private key must remain confidential.

For more information, please see Asymmetric Encryption.

Hybrid Implementation​

Utilizes asymmetric encryption to securely transfer a private key, which can then be used with symmetric encryption.

Storing Keys​

Best practices:

  • Store keys in secure hardwared modules
  • Encrypt keys when at rest
  • Transmit keys securely when used
  • Limit key access to regular audits and monitoring