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How to Encode / Decode a File

What is encoding / decoding ?

Encoding refers to the process of translating a file into an ASCII based string.
Decoding refers to the process of decoding the ASCII based string.

In order to perform this decoding/encoding process Base64 is typically used. Base64 is a program that  converts each 6 bits and then converts this to an ASCII based character out of a 64 ASCII character set. (this includes the characters of azAZ09+/.

Why would I want to do this ?

This is useful for situations were you need to transfer binary files across systems that have no network connectivity. Other applications were this is used is with SMTP which being a completely ASCII based protocol uses encoding to send any binary or not ASCII based data to the recipient.

Example

Below we will be encoding and decoding a floppy disc image.

1. On the first machine we will be encoding the file into an ASCII based string.
          Note : we use the file command to confirm the file type. 

[root@host1 tmp]# file vmscsi-1.2.0.4.flp
vmscsi-1.2.0.4.flp: DOS floppy 1440k, x86 hard disk boot sector
[root@host1 tmp]# base64 vmscsi-1.2.0.4.flp > vmscsi-1.2.0.4.flp.encoded
[root@host1 tmp]# head -n3 vmscsi-1.2.0.4.flp.encoded
6zyQTVNET1M1LjAAAgEBAALgAEAL8AkAEgACAAAAAAAAAAAAAAApUpcW7E5PIE5BTUUgICAgRkFU
MTIgICAzyY7RvPB7jtm4ACCOwPy9AHw4TiR9JIvBmeg8AXIcg+s6ZqEcfCZmOwcmilf8dQaAygKI
VgKAwxBz6zPJikYQmPdmFgNGHBNWHgNGDhPRi3YRYIlG/IlW/rggAPfmi14LA8NI9
[root@host1 tmp]# file vmscsi-1.2.0.4.flp.encoded
vmscsi-1.2.0.4.flp.encoded: ASCII text

2. Once we have copy and pasted the ASCII text to the other machine (into the file vmscsi-1.2.0.4.flp.encoded) we decode the file back into its original floppy image format.

[root@host2 tmp]# cat vmscsi-1.2.0.4.flp.encoded | base64 -di > vmscsi-1.2.0.4.flp.decoded
[root@host2 tmp]# file  vmscsi-1.2.0.4.flp.decoded
vmscsi-1.2.0.4.flp.decoded: DOS floppy 1440k, x86 hard disk boot sector

About the Author

RDonato

R Donato

Rick Donato is the Founder and Chief Editor of Fir3net.com. He currently works as a Principal Network Security Engineer and has a keen interest in automation and the cloud.

You can find Rick on Twitter @f3lix001