What's padded Base64 encoded strings and how can i generate them in ruby?

Question

Documentation for a Third-Party API that I'm working with states:

"[O]ur API only accepts padded Base64 encoded strings."

What are "padded Base64 encoded strings" and how can I generate them in Ruby. The code below is my first attempt at creating JSON formatted data converted to Base64.

  xa = Base64.encode64(a.to_json)

Answer 1

The padding they are talking about is actually part of Base64 itself. It's the "=" and "==" at the end. Base64 encodes packets of 3 bytes into 4 encoded characters. So if your input data has length n and

• n % 3 = 1 => "==" at the end for padding
• n % 3 = 2 => "=" at the end for padding

No need for you to change your code.

Answer 2

It looks like the base64 library pads by default; padding in Base64 would be the = characters on the end of the data.

You can see this by running the following in the irb console:

irb(main):002:0> require 'base64'
=> true
irb(main):003:0> Base64.encode64('a')
=> "YQ==\n"

Without the padding, you couldn't be sure whether YQ was everything or whether it was missing something.