The RFC 4648 (The Base16, Base32, and Base64 Data Encodings) defines different methods to encode binary data. Every Unix like system has the tool base64 installed to encode and decode data using the base64 alphabet. This alphabet includes the characters A-Z, a-z, 0-9, +, / for the data and = for padding. The base16 encoding scheme, better known as hex encoding, uses the alphabet 0-9 and A-F. This encoding is case-insensitive. The GNU coreutils do not include a base16 tool. I searched for a hex encoding and decoding tool with the same functionality as base64 without success. That’s why I wrote a script so I can use it to hex encode and decode binary data. Basically, it’s a wrapper around some Perl code.
The RFC 4648 (The Base16, Base32, and Base64 Data Encodings) tells us, that 4 bits can be represented by a character of the alphabeth of 0-9 and A-F. This is due to the fact, that 2^4 is 16 and the alpabeth has 16 different characters. Therefore, a byte uses two characters of this alpabeth.
This is an extract of the RFC:
8. Base 16 Encoding
The following description is original but analogous to previous
descriptions. Essentially, Base 16 encoding is the standard case-
insensitive hex encoding and may be referred to as “base16” or “hex”.
A 16-character subset of US-ASCII is used, enabling 4 bits to be
represented per printable character.
The encoding process represents 8-bit groups (octets) of input bits
as output strings of 2 encoded characters. Proceeding from left to
right, an 8-bit input is taken from the input data. These 8 bits are
then treated as 2 concatenated 4-bit groups, each of which is
translated into a single character in the base 16 alphabet.
Each 4-bit group is used as an index into an array of 16 printable
characters. The character referenced by the index is placed in the
Table 5: The Base 16 Alphabet
Value Encoding Value Encoding Value Encoding Value Encoding
0 0 4 4 8 8 12 C
1 1 5 5 9 9 13 D
2 2 6 6 10 A 14 E
3 3 7 7 11 B 15 F
Unlike base 32 and base 64, no special padding is necessary since a
full code word is always available.
The script base16 can be found on GitHub: https://github.com/emanuelduss/Scripts/blob/master/base16.
You can do a quick and dirty install using the following commands:
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 2574 100 2574 0 0 11817 0 --:--:-- --:--:-- --:--:-- 11861
$ sudo chmod 755 /usr/local/bin/base16
On Arch Linux, you can install base16 from the Arch User Repository (AUR):
The script base16 offers the same options and functionallty as the base64 tool. The usage can be displayed with the -h option:
Usage: base16 [OPTION]... [FILE]
Base16 (Hex) encode or decode FILE, or standard input, to standard output.
With no FILE, or when FILE is -, read standard input.
-d, decode data
-i, when decoding, ignore non-alphabet characters
-w COLS wrap encoded lines after COLS character (default 76).
Use 0 to disable line wrapping
-h display this help and exit
When decoding, the input may contain newlines in addition to the bytes of
the formal base64 alphabet. Use --ignore-garbage to attempt to recover
from any other non-alphabet bytes in the encoded stream.
For example, you can encode some data. When no file is provided, the data is read from standard input:
If you don’t like the linebreaks, use the -w 0 options do disable it:
This can then be decoded again using base16:
This is a test with a newline
- RFC 4648: The Base16, Base32, and Base64 Data Encodings: https://tools.ietf.org/html/rfc4648
- base16 in the Arch Linux User Repository (AUR): https://aur.archlinux.org/packages/base16/
- GNU Coreutils Tools: http://git.savannah.gnu.org/cgit/coreutils.git/tree/src