AES encrypt and decrypt using the web crypto API

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Wed Dec 22 2021 03:34:04 GMT+0000 (UTC)

Saved by @Explosion #javascript

const buff_to_base64 = (buff) => btoa(String.fromCharCode.apply(null, buff));

const base64_to_buf = (b64) =>
  Uint8Array.from(atob(b64), (c) => c.charCodeAt(null));

const enc = new TextEncoder();
const dec = new TextDecoder();

const getPasswordKey = (password) =>
  window.crypto.subtle.importKey("raw", enc.encode(password), "PBKDF2", false, [
    "deriveKey",
  ]);

const deriveKey = (passwordKey, salt, keyUsage) =>
  window.crypto.subtle.deriveKey(
    {
      name: "PBKDF2",
      salt: salt,
      iterations: 250000,
      hash: "SHA-256",
    },
    passwordKey,
    {
      name: "AES-GCM",
      length: 256,
    },
    false,
    keyUsage
  );

export async function encrypt(secretData, password) {
  try {
    const salt = window.crypto.getRandomValues(new Uint8Array(16));
    const iv = window.crypto.getRandomValues(new Uint8Array(12));
    const passwordKey = await getPasswordKey(password);
    const aesKey = await deriveKey(passwordKey, salt, ["encrypt"]);
    const encryptedContent = await window.crypto.subtle.encrypt(
      {
        name: "AES-GCM",
        iv: iv,
      },
      aesKey,
      enc.encode(secretData)
    );

    const encryptedContentArr = new Uint8Array(encryptedContent);
    let buff = new Uint8Array(
      salt.byteLength + iv.byteLength + encryptedContentArr.byteLength
    );
    buff.set(salt, 0);
    buff.set(iv, salt.byteLength);
    buff.set(encryptedContentArr, salt.byteLength + iv.byteLength);
    const base64Buff = buff_to_base64(buff);
    return base64Buff;
  } catch (e) {
    console.log(`Error - ${e}`);
    return "";
  }
}

export async function decrypt(encryptedData, password) {
  const encryptedDataBuff = base64_to_buf(encryptedData);
  const salt = encryptedDataBuff.slice(0, 16);
  const iv = encryptedDataBuff.slice(16, 16 + 12);
  const data = encryptedDataBuff.slice(16 + 12);
  const passwordKey = await getPasswordKey(password);
  const aesKey = await deriveKey(passwordKey, salt, ["decrypt"]);
  const decryptedContent = await window.crypto.subtle.decrypt(
    {
      name: "AES-GCM",
      iv: iv,
    },
    aesKey,
    data
  );
  return dec.decode(decryptedContent);
}
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https://explosion-scratch.github.io/blog/0-knowledge-auth/