v149 · JavaScript

WebCrypto Round-Trip

Encrypt a message with AES-GCM, then use Uint8Array.prototype.toBase64() to encode the ciphertext and IV for safe transport. Paste the base64 back in and use Uint8Array.fromBase64() to reconstruct the bytes before decrypting. The full encrypt → encode → decode → decrypt cycle in one page.

Generating AES-256-GCM key…

Encrypt

Plaintext message

1 IV (base64, 12 bytes)

—

2 Ciphertext (base64)

—

Decrypt

IV (base64) — auto-filled after encrypt

Ciphertext (base64) — auto-filled after encrypt

3 Decrypted plaintext

—
// 1. Encrypt and encode with toBase64()
const key = await crypto.subtle.generateKey(
  { name: 'AES-GCM', length: 256 },
  false, // non-exportable
  ['encrypt', 'decrypt']
);
const iv = crypto.getRandomValues(new Uint8Array(12));
const cipherBuf = await crypto.subtle.encrypt(
  { name: 'AES-GCM', iv },
  key,
  new TextEncoder().encode(plaintext)
);

const ivB64     = iv.toBase64();           // ← new API
const cipherB64 = new Uint8Array(cipherBuf).toBase64(); // ← new API

// 2. Decode and decrypt with fromBase64()
const ivBytes     = Uint8Array.fromBase64(ivB64);     // ← new API
const cipherBytes = Uint8Array.fromBase64(cipherB64); // ← new API
const decryptedBuf = await crypto.subtle.decrypt(
  { name: 'AES-GCM', iv: ivBytes },
  key,
  cipherBytes
);
const result = new TextDecoder().decode(decryptedBuf);

see also

implementation reference

Need the exact API surface, compatibility boundaries, errors, lifecycle, and source links? Read the matching gendn reference ↗