How to encode / decode files in windows?

Question

I want to write a simple java program that reverses all the bytes of a file. It should corrupt the file by encoding and make it accesible after decoding. Is there something I need to be aware of?

I'm asking this because I wrote a program like that in the past and it didn't work, because after decoding the file was still corrupted. Is there something I have to keep in mind like a header portion of the file or something?

Answer 1

If I understand this question, you can try: certutil.exe

• decode Hexadecimal:

  certutil -f -decodehex some_file.hex some_file_out.ext

• encode Hexadecimal:

  certutil -f -decodehex some_file.ext some_file_out.hex

• decode Base64:

  certutil -f -decode some_file.b64 some_file_out.ext

• encode Base64:

  certutil -f -encode some_file.ext some_file_out.b64

---

• For decode base64:

---

@echo off 

rem :: do some task #1 ::
rem :: do some task #2 ::
rem :: do some task #3 ::
rem :: ............... ::
rem :: do some task #n ::
rem :: ----------------::
rem :: decode (itself = %~f0) file in runtime 

2>nul >nul ( 
"%__appdir__%certutil.exe" -f -decode "%~f0" "%temp%\some_file_out_sample.txt"
) || goto :^(

rem :: do some another task #1 ::
rem :: do some another task #2 ::
rem :: do some another task #3 ::
rem :: ....................... ::
rem :: do some another task #n ::
rem :: ------------------------::

rem :: when finished :: 
exit /b

:^(
echo/Error decoding file & exit /b

-----BEGIN CERTIFICATE-----
IFRoaXMgaXMgZm9yIHNhbXBsZSBmaWxlIHRvIGVuY29kZS9kZWNvZGUNCg==
-----END CERTIFICATE-----

---

• For decode hexadecimal:

---

@echo off 

rem :: do some task #1 ::
rem :: do some task #2 ::
rem :: do some task #3 ::
rem :: ............... ::
rem :: do some task #n ::
rem :: ----------------::
rem :: echo/ hexdecimal string to file in runtime and decode 

(
   echo/0000 20 54 68 69 73 20 69 73  20 66 6f 72 20 73 61 6d
   echo/0010 70 6c 65 20 66 69 6c 65  20 74 6f 20 65 6e 63 6f
   echo/0020 64 65 2f 64 65 63 6f 64  65 0d 0a

) > "%temp%\some_file.hex" && ( 
2>nul >nul %__appdir__%certutil.exe -f -decodehex "%temp%\some_file.hex" "%temp%\some_file_out_sample.log"
) || goto :^(

rem :: do some another task #1 ::
rem :: do some another task #2 ::
rem :: do some another task #3 ::
rem :: ....................... ::
rem :: do some another task #n ::
rem :: -----------------------::

rem :: when finished :: 
exit /b

:^(
echo/Error decoding file & exit /b

Note: the base64 string will decode the file: "some_file_out_sample.txt/.log" with that into file:

"This is for sample file to encode/decode"