Base64 encoding

Here’s a breakdown of how Base64 encoding works, step by step:

1. Binary Data Grouping

• Base64 works on binary data. Your original data (text, image, etc.) is converted into a sequence of bytes (groups of 8 bits).
• These bytes are further grouped into sets of 3 bytes (totaling 24 bits).

2. Splitting into 6-bit Chunks

• Each group of 24 bits is divided into four 6-bit chunks.
• This is key because Base64 uses a set of 64 safe characters to represent data, and each 6-bit chunk can represent a value from 0-63.

3. Mapping to Base64 Characters

• Here’s a standard Base64 character table:
  • A-Z (values 0 - 25)
  • a-z (values 26 - 51)
  • 0-9 (values 52 - 61)
  • + (value 62)
  • / (value 63)
• Each 6-bit chunk is used as an index into this table. The corresponding character becomes the Base64 representation of that chunk.

4. Handling Padding

• If the original data length isn’t divisible by 3, special padding characters (=) are added to the end.
  • One = indicates the last group had only 8 useful bits.
  • Two = signs indicate the last group had only 16 useful bits.

Example: Encoding “Hi!”

1. Binary: “Hi!” in binary is 01001000 01101001 00100001
2. Grouping: 010010 000110 100100 100001
3. Mapping:
   • 010010 → S
   • 000110 → G
   • 100100 → k
   • 100001 → h
4. Result: “SGkh”

Why Base64?

• Safe Transport: Base64 uses printable ASCII characters, making the encoded data safe to include in emails, URLs, configuration files, etc.
• Overhead: Base64 encoding increases the size of the data by about 33% (4 output characters for every 3 input bytes).