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import { ENCRYPTION_KEY_BITS } from "../constants";
import { blobToArrayBuffer } from "./blob";
export const IV_LENGTH_BYTES = 12;
export const createIV = () => {
const arr = new Uint8Array(IV_LENGTH_BYTES);
return window.crypto.getRandomValues(arr);
};
export const generateEncryptionKey = async <
T extends "string" | "cryptoKey" = "string",
>(
returnAs?: T,
): Promise<T extends "cryptoKey" ? CryptoKey : string> => {
const key = await window.crypto.subtle.generateKey(
{
name: "AES-GCM",
length: ENCRYPTION_KEY_BITS,
},
true, // extractable
["encrypt", "decrypt"],
);
return (
returnAs === "cryptoKey"
? key
: (await window.crypto.subtle.exportKey("jwk", key)).k
) as T extends "cryptoKey" ? CryptoKey : string;
};
export const getCryptoKey = (key: string, usage: KeyUsage) =>
window.crypto.subtle.importKey(
"jwk",
{
alg: "A128GCM",
ext: true,
k: key,
key_ops: ["encrypt", "decrypt"],
kty: "oct",
},
{
name: "AES-GCM",
length: ENCRYPTION_KEY_BITS,
},
false, // extractable
[usage],
);
export const encryptData = async (
key: string | CryptoKey,
data: Uint8Array | ArrayBuffer | Blob | File | string,
): Promise<{ encryptedBuffer: ArrayBuffer; iv: Uint8Array }> => {
const importedKey =
typeof key === "string" ? await getCryptoKey(key, "encrypt") : key;
const iv = createIV();
const buffer: ArrayBuffer | Uint8Array =
typeof data === "string"
? new TextEncoder().encode(data)
: data instanceof Uint8Array
? data
: data instanceof Blob
? await blobToArrayBuffer(data)
: data;
// We use symmetric encryption. AES-GCM is the recommended algorithm and
// includes checks that the ciphertext has not been modified by an attacker.
const encryptedBuffer = await window.crypto.subtle.encrypt(
{
name: "AES-GCM",
iv,
},
importedKey,
buffer as ArrayBuffer | Uint8Array,
);
return { encryptedBuffer, iv };
};
export const decryptData = async (
iv: Uint8Array,
encrypted: Uint8Array | ArrayBuffer,
privateKey: string,
): Promise<ArrayBuffer> => {
const key = await getCryptoKey(privateKey, "decrypt");
return window.crypto.subtle.decrypt(
{
name: "AES-GCM",
iv,
},
key,
encrypted,
);
};
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