> For the complete documentation index, see [llms.txt](https://alham-rizvi.gitbook.io/alhamrizvi/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://alham-rizvi.gitbook.io/alhamrizvi/picoctf-writeups/picoctf/general-skills/undo.md).

# undo

### Step-by-Step Solution

#### Step 1 – Base64 Encoding

**Hint:** Base64 encoded the string

The input was Base64 encoded. Normally, you would decode using:

```bash
base64 -d
```

However, the challenge restricted arguments and pipes. The only accepted command was:

```bash
base64 -d
```

***

#### Step 2 – Reversed Text

**Hint:** Reversed the text

The string was reversed. To fix this:

```bash
rev
```

***

#### Step 3 – Underscores Replaced with Dashes

**Hint:** Replaced underscores with dashes

We needed to convert `-` back to `_`:

```bash
tr '-' '_'
```

***

#### Step 4 – Curly Braces Replaced with Parentheses

**Hint:** Replaced curly braces with parentheses

We reversed the transformation by converting parentheses back to braces:

```bash
tr '()' '{}'
```

***

#### Step 5 – ROT13 Encoding

**Hint:** Applied ROT13 to letters

ROT13 shifts each letter by 13 positions. Since `rot13` command was blocked, we used `tr`:

```bash
tr 'a-zA-Z' 'n-za-mN-ZA-M'
```

***

### Final Flag

```
picoCTF{Revers1ng_t3xt_Tr4nsf0rm@t10ns_0ea42cd0}
```


---

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