Add utilities to encrypt text.

src/utils/encryptionUtils.js

@@ -0,0 +1,19 @@
+// These functions accept and return Uint8Arrays
+
+export async function encryptAESGCM(plaintext, key) {
+    const iv = crypto.getRandomValues(new Uint8Array(12));
+    const algorithm = { name: "AES-GCM", iv: iv };
+    const keyMaterial = await crypto.subtle.importKey("raw", key, algorithm, false, ["encrypt"]);
+    const ciphertext = await crypto.subtle.encrypt(algorithm, keyMaterial, plaintext);
+
+    return new Uint8Array([...iv, ...new Uint8Array(ciphertext)]);
+}
+
+export async function decryptAESGCM(ciphertextArray, key) {
+    const iv = new Uint8Array(ciphertextArray.slice(0, 12));
+    const algorithm = { name: "AES-GCM", iv: iv };
+    const keyMaterial = await crypto.subtle.importKey("raw", key, algorithm, false, ["decrypt"]);
+    const decrypted = await crypto.subtle.decrypt(algorithm, keyMaterial, new Uint8Array(ciphertextArray.slice(12)));
+
+    return decrypted;
+}