Client-Side AES-GCM / CBC Encryptor & Decryptor

// Browser Native Web Crypto API Decryption
async function decryptAes(ciphertextB64, password, ivHex, saltHex, iterations = 100000) {
  const hexToBytes = (h) => new Uint8Array(h.match(/.{1,2}/g).map(byte => parseInt(byte, 16)));
  const b64ToBytes = (b) => Uint8Array.from(atob(b), c => c.charCodeAt(0));

  const salt = hexToBytes(saltHex);
  const iv = hexToBytes(ivHex);
  const ciphertext = b64ToBytes(ciphertextB64);

  const enc = new TextEncoder();
  const keyMaterial = await crypto.subtle.importKey(
    "raw", enc.encode(password), "PBKDF2", false, ["deriveKey"]
  );

  const key = await crypto.subtle.deriveKey(
    { name: "PBKDF2", salt, iterations, hash: "SHA-256" },
    keyMaterial,
    { name: "AES-GCM", length: 256 },
    false,
    ["decrypt"]
  );

  const decrypted = await crypto.subtle.decrypt(
    { name: "AES-GCM", iv, tagLength: 128 },
    key,
    ciphertext
  );

  return new TextDecoder().decode(decrypted);
}

// Example Execution:
decryptAes("YOUR_CIPHERTEXT_BASE64...", "YOUR_PASSWORD", "", "")
  .then(console.log);