Base32 Encoding Algorithm

This section describes the Base32 encoding algorithm with some simple encoding examples.

Base32 encoding algorithm is designed to encode any binary data, an stream of bytes, into a stream of 32-printable characters.

Comparing with Base64 encoding, Base32 uses a much smaller set of characters which has three main advantages:

Obviously, the main disdvantage of Base32 is that the resusting string is about 20% longer than Base64.

The most widely used Base32 character set is defined in RFC 3548. It uses an alphabet of A-Z, followed by 2-7. 0 and 1 are skipped due to their similarity with the letters O and I. Those 32 characters are mapped to integer values are below:

   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
       7 H            16 Q            25 Z
       8 I            17 R            26 2

The Base32 encoding process is to:

Example 1: Input data: 1 byte, "A". Encoded output: 8 characters, "IE======"

Input Data          A
Input Bits   01000001
Padding      01000001  00000000  00000000 00000000 00000000
                  \      |    \      |     |    \     \
Bit Groups   01000 00100 00000 00000 00000 00000 00000 00000
Mapping          I     E     A     A     A     A     A     A
Overriding       I     E     =     =     =     =     =     =

Example 2: Input data: 2 bytes, "AB". Encoded output, 8 characters, "IFBA===="

Input Data          A         B
Input Bits   01000001  01000010
Padding      01000001  01000010  00000000 00000000 00000000
                  \      |    \      |     |    \     \
Bit Groups   01000 00101 00001 00000 00000 00000 00000 00000
Mapping          I     F     B     A     A     A     A     A
Overriding       I     F     B     A     =     =     =     =

Example 3: Input data: 3 bytes, "ABC". Encoded output, 8 characters, "IFBEG==="

Input Data          A         B         C
Input Bits   01000001  01000010  01000011
Padding      01000001  01000010  01000011 00000000 00000000
                  \      |    \      |     |    \     \
Bit Groups   01000 00101 00001 00100 00110 00000 00000 00000
Mapping          I     F     B     E     G     A     A     A
Overriding       I     F     B     E     G     =     =     =

Example 4: Input data: 4 bytes, "ABCD". Encoded output, 8 characters, "IFBEGRA="

Input Data          A         B         C        D
Input Bits   01000001  01000010  01000011 01000100
Padding      01000001  01000010  01000011 01000100 00000000
                  \      |    \      |     |    \     \
Bit Groups   01000 00101 00001 00100 00110 10001 00000 00000
Mapping          I     F     B     E     G     R     A     A
Overriding       I     F     B     E     G     R     A     =

Example 5: Input data: 5 bytes, "ABCDE". Encoded output, 8 characters, "IFBEGRCF"

Input Data          A         B         C        D        E
Input Bits   01000001  01000010  01000011 01000100 01000101
Padding      01000001  01000010  01000011 01000100 01000101
                  \      |    \      |     |    \     \
Bit Groups   01000 00101 00001 00100 00110 10001 00010 00101
Mapping          I     F     B     E     G     R     C     F
Overriding       I     F     B     E     G     R     C     F

Table of Contents

 About This Book

 Base64 Encoding

 Base64 Encoding and Decoding Tools

 Base64URL - URL Safe Base64 Encoding

Base32 Encoding

Base32 Encoding Algorithm

 Base32 Character Set Maps

 Bitpedia Implementation of Base32 in Java

 Bitpedia Implementation of Base32 in Java - Test

 Andre's Implementation of Base32 in PHP

 Andre's Implementation of Base32 in PHP - Test

 madebits Implementation of Base32 in C++

 URL Encoding, URI Encoding, or Percent Encoding

 UUEncode Encoding

 References

 Full Version in PDF/EPUB