feat: encrypt() and decrypt() methods (#171)

mod.ts

@@ -6,3 +6,56 @@ export { Context } from './context.ts'
 export { Exception } from './exception.ts'
 export { createExtension } from './extensions.ts'
 export type { Extension } from './extensions.ts'
+
+/* crypto ------------------------------------------------------------------- */
+
+import { decode } from 'https://deno.land/std@0.198.0/encoding/base64.ts'
+
+export async function encrypt(key: string, message: string) {
+  const iv = crypto.getRandomValues(new Uint8Array(12)),
+    ivStr = Array.from(iv)
+      .map((byte) => String.fromCharCode(byte))
+      .join(''),
+    alg = { name: 'AES-GCM', iv },
+    cryptoKey = await crypto.subtle.importKey(
+      'raw',
+      decode(key).buffer,
+      alg,
+      true,
+      ['encrypt', 'decrypt'],
+    ),
+    cipherBuf = await crypto.subtle.encrypt(
+      alg,
+      cryptoKey,
+      new TextEncoder().encode(message),
+    ),
+    cipherArr = Array.from(new Uint8Array(cipherBuf)),
+    cipherStr = cipherArr.map((byte) => String.fromCharCode(byte))
+      .join('')
+
+  return btoa(ivStr + cipherStr)
+}
+
+export async function decrypt(key: string, message: string) {
+  const iv = atob(message).slice(0, 12),
+    alg = {
+      name: 'AES-GCM',
+      iv: new Uint8Array(
+        Array.from(iv).map((char) => char.charCodeAt(0)),
+      ),
+    },
+    cryptoKey = await crypto.subtle.importKey(
+      'raw',
+      decode(key).buffer,
+      alg,
+      true,
+      ['encrypt', 'decrypt'],
+    ),
+    cipherStr = atob(message).slice(12),
+    cipherBuf = new Uint8Array(
+      Array.from(cipherStr).map((char) => char.charCodeAt(0)),
+    ),
+    buf = await crypto.subtle.decrypt(alg, cryptoKey, cipherBuf)
+
+  return new TextDecoder().decode(buf)
+}