Base64 decoding is the process of converting Base64-encoded data back to its original binary or text form. It reverses the encoding process, retrieving the original data from the Base64 representation.
To decode Base64 data, the following steps are typically followed:
1. Retrieve the Base64-encoded data that you want to decode.
2. If there is any padding at the end of the encoded data (represented by '=' characters), remove it. Note that padding is only added when the number of bytes in the original data is not a multiple of three.
3. Convert each character in the Base64-encoded data to its corresponding 6-bit binary value according to the Base64 character set.
4. Combine the 6-bit binary values to form groups of three bytes (24 bits).
5. If the number of characters in the Base64-encoded data is not a multiple of four, adjust the grouping accordingly.
6. The resulting groups of three bytes form the decoded binary data.
Here's an example to illustrate the Base64 decoding process:
Base64-encoded data: aW5m (corresponding to binary: 011010 010110 111011 001101)
Grouped into three bytes: 01101001 01101110 01100110 01101111 (24 bits)
Converted to ASCII characters: inf
In programming languages, you can often find built-in functions or libraries that provide Base64 decoding capabilities. These functions take the Base64-encoded data as input and return the decoded binary or text data.
Base64 decoding is commonly used in various scenarios, such as:
- Decoding Base64-encoded attachments in email messages.
- Extracting binary data from Base64-encoded strings received over HTTP.
- Converting Base64-encoded data in XML or JSON documents back to its original form.
It's worth noting that the Base64 encoding/decoding process is not a form of encryption or security measure. It is primarily used for data representation and compatibility with systems that only support ASCII characters.