Learning Malware Analysis

1.2.1 Translating Data To Base64

Standard Base64 encoding consists of the following 64-character set. Each 3 bytes (24 bits) of the binary data that you want to encode is translated into four characters from the character set mentioned later. Each translated character is 6 bits in size. In addition to the following characters, the = character is used for padding:

ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/

To understand how the data is translated into Base64 encoding, first, build the Base64 index table by assigning index 0 to 63 to the letters in the character set, as shown here. As per the following table, the index 0 corresponds to the letter A and the index 62 corresponds to +, and so on:

Now, let's say we want to ...