This code demonstrates how to use Unicode Variation Selectors to encode and decode hidden messages.

unicodeMalwareVariantionSelectors.mjs

/**
 * This code demonstrates how to use Unicode Variation Selectors to encode and decode hidden messages.
 *
 * It defines two functions: `encoder` to convert a string into a sequence of Unicode characters that 
 * represent the bytes of the original string, and `decoder` to reverse this process and retrieve the 
 * original string from the hidden Unicode characters.
 *
 * The `encoder` function takes a string, converts it to a buffer of bytes, and then maps each byte to
 * a corresponding Unicode character. If the byte value is 15 or less, it uses the range U+FE00 to U+FE0F; 
 * if it's greater than 15, it uses the range U+E0100 to U+E01EF.
 *
 * The `decoder` function takes the hidden Unicode string, extracts the code points of each character, and
 * determines whether they fall within the specified ranges. It then reconstructs the original byte values
 * and converts them back to a UTF-8 string.
 */

function encoder(text) {
  return [...Buffer.from(text, "utf-8")]
    .map((byte) =>
      String.fromCodePoint(byte <= 15 ? 0xfe00 + byte : 0xe0100 + byte - 16),
    )
    .join("");
}

function decoder(hiddenText) {
  const bytes = [...hiddenText]
    .map((char) => {
      const w = char.codePointAt(0);
      if (w >= 0xfe00 && w <= 0xfe0f) return w - 0xfe00;
      if (w >= 0xe0100 && w <= 0xe01ef) return w - 0xe0100 + 16;
      return null;
    })
    .filter((n) => n !== null);

  return Buffer.from(bytes).toString("utf-8");
}

const payload = "Hello, World!";
const hidden = encoder(payload);
const revealed = decoder(hidden);

console.log("Payload:", payload);
console.log("Hidden:", hidden);
console.log("Revealed:", revealed);