📦 Base64 Encoding / Decoding for File Transfers

📦 Base64 Encoding / Decoding for File Transfers

Want to move files between systems without network tools? 🤯 You can use Base64 encoding via the terminal to do just that! It’s perfect for quick transfers between machines where you have terminal access but not much else.

---

🛡️ Step 1: Check the File’s MD5 Hash

Let’s say you have a file like an SSH private key. First, check its MD5 hash to verify integrity later:

z3tssu@htb[/htb]$ md5sum id_rsa

✅ Example Output:

4e301756a07ded0a2dd6953abf015278  id_rsa

---

📤 Step 2: Encode the File to Base64

Use cat and base64 to turn your file into a string:

z3tssu@htb[/htb]$ cat id_rsa | base64 -w 0; echo

• -w 0 puts everything on one line (easier to copy 📋)

• echo helps with formatting by creating a new line

You’ll get a long Base64 string like this:

LS0tLS1CRUdJTiBPUEVOU1NIIFBSSVZBVEUgS0VZLS0tLS0K...

---

📥 Step 3: Transfer & Decode the File on the Target

Paste the Base64-encoded content on your target machine and decode it:

z3tssu@htb[/htb]$ echo -n 'PASTE-YOUR-BASE64-STRING-HERE' | base64 -d > id_rsa

🔁 This converts the Base64 back into the original file and saves it as id_rsa.

---

🧪 Step 4: Verify the File with MD5

Run md5sum again on the decoded file to confirm the hash matches:

z3tssu@htb[/htb]$ md5sum id_rsa

✅ Should return:

4e301756a07ded0a2dd6953abf015278  id_rsa

If the hashes match, the transfer was perfectly successful! 🎉

---

Transfer Files in Reverse

You can also use this method in reverse! From your compromised machine, use:

cat <filename> | base64 -w 0

Then decode the output on your Pwnbox or local system using:

echo -n '<base64_string>' | base64 -d > <filename>

---