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Breaking: Using deriveBits instead of encryption for the storage url #24

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Breaking: Using deriveBits instead of encryption for the storage url #24

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26 changes: 23 additions & 3 deletions src/utils/safeDoc.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -20,11 +20,10 @@ export {
} from "@/utils/codecs";

const PAGE_SALT = codecs.base64.decode("Ljeijq98ZyaFa5NV");
const PAGE_KEY = "4sQNniS/0141scm8";
const DERIVE = {
name: "PBKDF2",
salt: PAGE_SALT,
iterations: 100000,
iterations: Math.pow(2, 16),
hash: "SHA-256",
} as const satisfies Pbkdf2Params;
const ENCRYPT = {
Expand Down Expand Up @@ -91,7 +90,28 @@ async function decryptDocument(

const publicKeys = autoLru(10, async (privateKeyBase64) =>
codecs.crockfordBase32.encode(
await encrypt(PAGE_KEY, codecs.base64.decode(privateKeyBase64)),
new Uint8Array(
await crypto.subtle.deriveBits(
{
...DERIVE,
//
// Passwords are set to provide 96 bits of entropy.
// For 128 bit to be safe for brute force attacks we need 2^(120-96) or 2^32 iterations.
//
// See section A.2.2 of NIST SP 800-132 - https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-132.pdf
//
// That said, 2^32 operations exceed the 2^32-1 limit of PBKDF2 and for it to be practically usable
// we need to limit ourselves to 2^22 operations for a brute force complexity equal to 118bit of entropy.
//
// With 118bit considering https://bruteforce.bitsnbites.eu/ the computation time should still be practically
// unreachable.
//
iterations: Math.pow(2, 22),
},
await derivationKeys.get(privateKeyBase64),
128,
),
),
),
);

Expand Down