Encode

Encoding data is a process of converting data from one format into a new format. In the context of web development, there are two main types of encoding: character encoding and data encoding.

Example

1. Character encoding:

   • HTML Encoding (HTML escape): Special characters (like <, >, &, etc.) in HTML documents need to be encoded to ensure that browsers interpret them corrrectly

     • < ⇒ <

     • ⇒ >

   • URL Encoding: When passing data in URLs, special characters that are not allowed in URLs or have a special meaning (such as space or “&”) need to be encoded

     • space ⇒ %20

     • & ⇒ %26

     • https://www.google.com/search?q=嗨妳好 ⇒ https://www.google.com/search?q=%E5%97%A8%E5%A6%B3%E5%A5%BD

       encodeURI() and decodeURI()

       

       encodeURI() and decodeURI()

   • UTF-8 Encoding: UTF-8 is a character encoding that represents each character in the Unicode character set. It is widely used for encoding text on the web to support internationalization and multilingual content.

2. Data Encoding:

   • Base64 Encoding: This is a binary-to-text encoding scheme where binary data is encoded using a set of 64 characters, consisting of letters, digits, and symbols. It is commonly used for encoding binary data, such as images or files, into a text format that can be transmitted over text-based protocols like email or included in data URLs.

     • cat image.png | base64

       

       Encode an image with base64

   • Form Data Encoding: When submitting form data in an HTTP request, the data is usually URL-encoded or sent as multipart/form-data, depending on the content type specified in the request.

3. Security Considerations:
   • HTML/CSS/Javascript Encoding: To prevent Cross-Site Scripting (XSS) attacks, user input should be properly encoded when rendered in HTML, CSS or Javascript.
   • SQL Encoding: To prevent SQL injection attacks, user input should be properly encoded or parameterized before being included in SQL queries.

Encrypt

Symmetric Encrypt

The symmetric key cryptography method uses the same key for encrypting and decrypting.

pros and cons

• pros
  • fast, easy to use for big data
• cons
  • since using the same key to encrypt and decrypt, it provides less security and increases the chances of the key being stolen.

Asymmetric Encrypt

The asymmetric key method uses two different keys (the public key and the private key) to encrypt and decrypt data.

• public key:
  • used for encrypting data
  • it’s openly available to anyone
• private key:
  • used for decrypting data
  • Should be only known to the data receiver

pros and cons

• pros:
  • more secure than the symmetric method, as an unauthorized person would need to hack the two keys to completely compromise any given system.
• cons:
  • slow, so it’s mainly used for sending a small volume of data

Example