CERTIFICATE

Challenge

We are given a certificate generator at:

https://eth007.me/cert/

The HTML/JS shows how the flag is created. Inside the script there is a function:

function customHash(str){
  let h = 1337;
  for (let i=0;i<str.length;i++){
    h = (h * 31 + str.charCodeAt(i)) ^ (h >>> 7);
    h = h >>> 0;
  }
  return h.toString(16);
}

function makeFlag(name){
  const clean = name.trim() || "anon";
  const h = customHash(clean);
  return `ictf{${h}}`;
}

The SVG certificate stores the flag inside the <desc> tag.

However, if you type Eth007 as the participant name, the code replaces it with REDACTED:

if (name == "Eth007") {
    name = "REDACTED"
}

So we can’t just generate it directly from the site.

Solution

We run the custom hash function locally with the input "Eth007". That produces:

7b4b3965

So the final flag is:

ictf{7b4b3965}

Flag

ictf{7b4b3965}