Intro To 'base32' Command In Linux

2023-06-17 - By Robert Elder

I use the 'base32' command to encode or decode from base32 encoding:

echo "base32" | base32

MJQXGZJTGIFA====

Base 32 Encoding & Decoding

If I pipe this hello world statement into the 'base32' command, I'll see the following string of base 32 characters:

echo "Hello World!" | base32

JBSWY3DPEBLW64TMMQQQU===

I can also decode this same base 32 encoded string by using the '-d' flag:

echo "JBSWY3DPEBLW64TMMQQQU===" | base32 -d

Hello World!

RFC 4648

The 'base32' character set is defined in request for comment 4648. In this table, you can see that the 'base32' encoding uses all 26 uppercase letters of the alphabet and the six numerical digits from 2 to 7:

RFC 4648                    Base-N Encodings                October 2006


   Each 5-bit group is used as an index into an array of 32 printable
   characters.  The character referenced by the index is placed in the
   output string.  These characters, identified in Table 3, below, are
   selected from US-ASCII digits and uppercase letters.

                     Table 3: The Base 32 Alphabet

     Value Encoding  Value Encoding  Value Encoding  Value Encoding
         0 A             9 J            18 S            27 3
         1 B            10 K            19 T            28 4
         2 C            11 L            20 U            29 5
         3 D            12 M            21 V            30 6
         4 E            13 N            22 W            31 7
         5 F            14 O            23 X
         6 G            15 P            24 Y         (pad) =
         7 H            16 Q            25 Z
         8 I            17 R            26 2

Additionally, an equal sign character is used for padding.

Purpose Of Base 32 Encoding

The 'base32' command is useful for reliably encoding non-printable binary characters into a form that can't be easily corrupted by other programs:

echo -n -e '\x00\x01\x02\x95\x96\x97' | xxd
echo -n -e '\x00\x01\x02\x95\x96\x97' | base32 | base32 -d | xxd

00000000: 0001 0295 9697                           ......
00000000: 0001 0295 9697                           ......

Base 32 Vs. Base 64

Base 32 is immune to information loss from capitalization changes. Here is a command that will capitalize all of the letters in a base32 encoded string and then try to decode it:

echo 'Hello World!' | base32 | tr 'A-Z' 'a-z' | tr 'a-z' 'A-Z' | base32 -d

Hello World!

As you can see from the output above, the original input string can still be recovered.

However, for base 64 encoding this is not the case:

echo 'Hello World!' | base64 | tr 'A-Z' 'a-z' | tr 'a-z' 'A-Z' | base64 -d

HeRoWoX

As you can see from the output above, the string has become corrupted.

Disadvantage Of Base 32

One disadvantage of base 32 is that it will use more characters than base 64 when representing the same piece of data. Let's use this command to sample 100 bytes of random data into the file 'some-data':

head -c 100 /dev/urandom > some-data

Now, here is that data encoded as a base 32 encoded string:

cat some-data | base32

BLQMD4KSP62FFTZ7VQ5ZUP5QFB6WAG6O2VNNIPMOPLSZVCFF4FXAWPGFIUDTM4D23NP25NEZAVWK
AC2XYIJ3BH2AVS7EEJSTJNVKSKS5QA32W3Q6XUNKITUIWL23WPGYCURKZW4QDXAYC64BJO4E4HGI
EVVXZ4OZ

and, here is that same data encoded as a base 64 encoded string:

cat some-data | base64

CuDB8VJ/tFLPP6w7mj+wKH1gG87VWtQ9jnrlmoil4W4LPMVFBzZwettfrrSZBWygC1fCE7CfQKy+
QiZTS2qpKl2AN6tuHr0apE6IsvW7PNgVIqzbkB3BgXuBS7hOHMgla3zx2Q==

As you can see from the above output, the base 64 encoded string is much shorter than the base 32 encoded string.

And that's why the 'base32' command is my favourite Linux command.

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