Can a base64 encoded string contain whitespace?

Question

Might a base64 encoded string contain whitespace? Specifically, could it contain whitespace at the end of the string?

PS. I'm thinking about the whole "MySQL will trim trailing whitespace when storing strings in VARCHAR fields" here ;-)

Answer 1

No it can't. See Base64 for the allowed character repository used by base64, which are the characters A-Z, a-z, 0-9, + and / (the last two may differ depending on the implementation) as well as the padding character = (but that's also implementation dependent as some implementations don't use padding at all).

Answer 2

It shouldn't, but it might do.

A valid base64 string should not contain whitespace since the encoding alphabet should only consist of A-Z a-z 0-9 + /

However, if the encoded data happens to contain a '+' character, and the data is passed in a URL, it can be unintentionally converted into a space. So you may come across a supposed base64 string that appears to have spaces in it under these circumstances.

If this is the case, simply replace spaces with pluses before decoding.

PS. I'm thinking about the whole "MySQL will trim trailing whitespace when storing strings in VARCHAR fields" here

As an aside, the trailing whitespaces of a varchar won't be casually stripped as of MySQL 5.0.3

Answer 3

Yes. Base64-encoded string can contain white-spaces but the characters are not significant. So it's ok if database trims spaces.

As a matter of fact, the original MIME specification recommends to break Base64 strings into lines of 72 characters. base64Binary of XML may also include newlines, tabs, spaces.

In PHP, base64_decode() strips all whiltespace characters so you don't have to worry about it.

Answer 4

Wikipedia suggests that there're like a gazillion variations of the Base64 encoding:

http://en.wikipedia.org/wiki/Base64

So the answer probably depends on what you need to do with the string. But I'd dare say you created in PHP with base64_encode() so it appears to be safe to append blanks:

<?php

$original_data = 'Lorem ipsum dolor sit amet';
$encoded_data = base64_encode($original_data);
$padded_data = '    ' . chunk_split($encoded_data, 3, '  ') . '    ';

echo base64_decode($padded_data); // Prints 'Lorem ipsum dolor sit amet'

?>

Answer 5

No, but - some implementations of the base64 utility will add linebreaks to the output, which can make it appear as though whitespace is part of the output. If you're running into this case, depending on your version of base64, you can either turn off this behavior, or strip newline characters, by doing one of the following:

base64 -w 0 < input.txt
base64 < input | tr -d \\n

See this question for more detail: https://superuser.com/questions/1225134/why-does-the-base64-of-a-string-contain-n/1225334

Answer 6

As far as I know it cannot. Basically a Base64 string must be constructed from a set of 64 characters. A-Z, a-z, 0-9 make 62 - the other two depend on the implementation.

Based on what I know, there is now implementation that will use white space as a character. Main reason for that is readability - i.e. a Base64 string must be easily printed and recognized.

You'd probably find more info about it on Wikipedia.