What is Base64? (Cryptography Cipher)

About

Base64 is a cipher (without key and reversible) that converts (encode) a data (message) in 64 characters of the ASCII string.

This encoding doesn't protect the value from anything other than an over-the-shoulder glance.

Decoder / Encoder

See also the Google encoder/decoder

Usage

• for datastore that accepts only ASCII string format
• to have a portable version of the data between systems. ie get rid of:
  • EOL
  • or whitespace
• having data encoded on only 64 characters (ie without the point for instance)

Example: base64 is used in the basic authentication scheme to encode the value.

Steps

Encode

• The Clear Text (ie message to encode)

A text message with only string

• Transform the text into binary data by applying the character set table conversion
• Transform the binary into a succession of characters with the alphabet conversion table
• add the optional trailing character =
• and you get the base64 cipher

Decode

The decode steps are the same as the encode steps but in reverse. You need to use the encoded character as input.

Syntax

A base64 value has the following format:

base64Conversion=

where:

• base64Conversion is the conversion when the alphabet conversion is applied
• = is one or several optional trailing character

Alphabet

The alphabet is the conversion table between binary data (base 2) and its equivalent:

• in base64 number
• in character
• in character in a URL

Management

Javascript Node

const base64 =  Buffer.from('Hello Base 64').toString('base64');

atob / btoa javascript function are deprecated.

Javascript

const base64 = window.btoa("Hello World");
console.log(`Base64: ${base64}`);
const plainText = window.atob(base64);
console.log(`Plain Text: ${plainText}`);

To decode a base64 URL encoding:

function base64Decode(s){
  // from base64 url to base 64
  s = s
       .replace(/-/g, '+')
       .replace(/_/g, '/');
  return window.atob(s);
}

See the decoder/encoder script above.

Ref:

• WebApi Ref
• Mozilla Btoa Javascript Function

base64 command utility

cat my-file | base64

Open Ssl

Openssl

echo Hello World ! | openssl base64

SGVsbG8gV29ybGQgIQo=

Java

String encode = Base64.getEncoder().encodeToString("Foo".getBytes());
byte[] decode = Base64.getDecoder().decode(encode);
System.out.println(new String(decode,StandardCharsets.UTF_8));

Foo

Documentation / Reference

• rfc4648 - The Base16, Base32, and Base64 Data Encodings