Šepot — end-to-end encrypted messenger
Initial public release. Anonymous on-device identity (no phone number, e-mail, or password), Signal-protocol cryptography (X3DH + PQXDH, Double Ratchet, sealed sender) via libsignal, a metadata-minimizing relay, group chats, disappearing messages, encrypted local storage, optional Tor transport, and a UI localized into Czech, English, German, Russian, and Italian. Monorepo: Flutter client (app/), Rust relay + wire types (rust/), protobuf definitions (proto/), self-host deploy (deploy/). Licensed under AGPL-3.0 with an app-store distribution exception (§7).
This commit is contained in:
Julius Joska
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import 'dart:convert';
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import 'dart:typed_data';
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import 'package:base32/base32.dart';
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import 'package:base32/encodings.dart';
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import 'package:pointycastle/digests/blake2b.dart';
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import 'package:sepot/core/crypto/mnemonic.dart';
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import 'package:sepot/core/crypto/sepot_crypto.dart';
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/// Fingerprint identity — jediné user-facing ID Šepotu.
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///
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/// fingerprint = BLAKE2b-256( serializovaný identity pubkey, 33 B )
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///
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/// Zobrazuje se jako Crockford base32 (52 znaků), zkráceně „SEP-XXXXXXXXXX".
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/// POZOR: NEPLÉST s `account_id` — to je náhodný 16B routing handle, který
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/// přiděluje relay při registraci a nemá k identitě kryptografický vztah.
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class SepotFingerprint {
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SepotFingerprint(this.bytes)
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: assert(bytes.length == 32, 'BLAKE2b-256 = 32 bytes');
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/// Spočítá fingerprint ze serializovaného veřejného identity klíče.
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factory SepotFingerprint.ofPublicKey(Uint8List identityPublicKey) {
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final digest = Blake2bDigest(digestSize: 32);
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return SepotFingerprint(digest.process(identityPublicKey));
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}
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final Uint8List bytes;
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/// Plné zobrazení — 52 znaků Crockford base32, bez paddingu.
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String get display =>
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base32.encode(bytes, encoding: Encoding.crockford).toUpperCase();
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/// UX zkratka do titulků, QR popisků a seznamů.
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String get short => 'SEP-${display.substring(0, 10)}';
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@override
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String toString() => display;
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@override
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bool operator ==(Object other) =>
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other is SepotFingerprint && display == other.display;
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@override
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int get hashCode => display.hashCode;
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}
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/// Lokální identita uživatele — identity keypair + zobrazované jméno.
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///
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/// Identita = klíč. Žádné UUID, žádný telefon, žádný e-mail. Obnova
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/// přes 24slovný mnemonic (reverzibilní enkódování privátního klíče).
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class LocalIdentity {
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LocalIdentity({
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required this.displayName,
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required this.identityPrivateKey,
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required this.identityPublicKey,
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required this.createdAt,
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}) : fingerprint = SepotFingerprint.ofPublicKey(identityPublicKey);
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final String displayName;
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/// 32 B, serializovaný (clampnutý). Nikdy neopouští zařízení jinak než
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/// jako mnemonic záloha uživatele. ZÁKAZ kopírování do schránky.
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final Uint8List identityPrivateKey;
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/// 33 B, serializovaný (libsignal type byte + 32 B).
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final Uint8List identityPublicKey;
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final DateTime createdAt;
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final SepotFingerprint fingerprint;
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/// Vytvoř novou identitu (onboarding).
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static Future<LocalIdentity> create(String displayName) async {
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final keys = SepotCrypto.generateIdentityKeys();
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return LocalIdentity(
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displayName: displayName,
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identityPrivateKey: keys.privateKey,
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identityPublicKey: keys.publicKey,
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createdAt: DateTime.now(),
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);
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}
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/// Obnov identitu z 24slovného mnemonic (recovery flow).
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///
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/// Obnoví IDENTITU (stejný klíč → stejný fingerprint → „verified"
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/// kontakty drží), ne historii zpráv — ta je díky forward secrecy pryč
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/// a UI to musí říct.
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static Future<LocalIdentity> recover({
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required List<String> mnemonicWords,
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required String displayName,
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}) async {
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final privateKey = SepotMnemonic.decode(mnemonicWords);
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return LocalIdentity(
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displayName: displayName,
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identityPrivateKey: privateKey,
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identityPublicKey: SepotCrypto.derivePublicKey(privateKey),
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createdAt: DateTime.now(),
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);
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}
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/// 24 slov zálohy identity. Zobrazit jen v chráněném recovery UI.
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List<String> get mnemonic => SepotMnemonic.encode(identityPrivateKey);
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/// Kompatibilní alias — dřív tu bylo UUID, teď je ID totožné
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/// s fingerprintem (deterministicky z klíče).
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String get id => fingerprint.display;
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/// Šepot ID pro zobrazení v UI.
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String get sepotId => fingerprint.short;
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/// Veřejná identita (bezpečné ke sdílení).
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PublicIdentity get publicIdentity => PublicIdentity(
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displayName: displayName,
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identityKey: identityPublicKey,
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createdAt: createdAt,
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);
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Map<String, dynamic> toJson() => {
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'v': 2,
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'displayName': displayName,
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'identityPrivateKey': base64Encode(identityPrivateKey),
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'identityPublicKey': base64Encode(identityPublicKey),
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'createdAt': createdAt.toIso8601String(),
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};
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factory LocalIdentity.fromJson(Map<String, dynamic> json) {
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if (json['v'] != 2) {
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throw const FormatException(
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'Unsupported identity format (pre-libsignal era) — new onboarding required',
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);
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}
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return LocalIdentity(
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displayName: json['displayName'] as String,
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identityPrivateKey: base64Decode(json['identityPrivateKey'] as String),
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identityPublicKey: base64Decode(json['identityPublicKey'] as String),
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createdAt: DateTime.parse(json['createdAt'] as String),
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);
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}
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}
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/// Veřejná identita — bezpečné ke sdílení, pro QR kódy a `sepot://` odkazy.
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///
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/// Vedle krypto identity (identity klíč → fingerprint) nese i ROUTING:
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/// `accountId` (náhodný server handle — pojmenovává libsignal session
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/// odesílatele, musí sedět se SenderCertificate) a `deliveryAddress`
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/// (32B blind token, podle kterého relay směruje obálky). Bez nich nejde
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/// kontaktu poslat první zpráva. Obě pole jsou náhodná — s identitou je
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/// spojuje jen sám uživatel tím, že je sdílí ve svém odkazu.
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class PublicIdentity {
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PublicIdentity({
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required this.displayName,
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required this.identityKey,
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required this.createdAt,
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this.accountId,
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this.deliveryAddress,
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}) : fingerprint = SepotFingerprint.ofPublicKey(identityKey);
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final String displayName;
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/// 33 B, serializovaný veřejný identity klíč.
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final Uint8List identityKey;
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final DateTime createdAt;
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final SepotFingerprint fingerprint;
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/// Hex accountId na relayi (null = ještě neregistrováno / neznámo).
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final String? accountId;
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/// 32 B routing token na relayi (null = neznámo).
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final Uint8List? deliveryAddress;
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static const _linkPrefix = 'sepot://add/';
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/// Kompatibilní alias na fingerprint (dřív UUID).
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String get id => fingerprint.display;
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/// Šepot ID pro zobrazení.
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String get sepotId => fingerprint.short;
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PublicIdentity withRouting({
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required String accountId,
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required Uint8List deliveryAddress,
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}) =>
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PublicIdentity(
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displayName: displayName,
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identityKey: identityKey,
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createdAt: createdAt,
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accountId: accountId,
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deliveryAddress: deliveryAddress,
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);
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/// Export jako `sepot://add/...` odkaz (obsah QR kódu i sdílený link).
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String toShareString() {
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final payload = base64UrlEncode(
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utf8.encode(jsonEncode({
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'v': 2,
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'n': displayName,
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'ik': base64Encode(identityKey),
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'ts': createdAt.toIso8601String(),
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if (accountId != null) 'aid': accountId,
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if (deliveryAddress != null) 'da': base64Encode(deliveryAddress!),
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})),
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);
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return '$_linkPrefix$payload';
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}
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/// Import z odkazu / QR. Vrací null, pokud vstup není platný.
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static PublicIdentity? fromShareString(String s) {
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try {
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var payload = s.trim();
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if (payload.startsWith(_linkPrefix)) {
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payload = payload.substring(_linkPrefix.length);
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}
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final map = jsonDecode(utf8.decode(base64Url.decode(payload)))
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as Map<String, dynamic>;
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if (map['v'] != 2) return null;
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final identityKey = base64Decode(map['ik'] as String);
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if (identityKey.length != 33) return null;
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final da = map['da'] as String?;
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Uint8List? deliveryAddress;
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if (da != null) {
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deliveryAddress = base64Decode(da);
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// deliveryAddress je 32B routing token — vadný odkaz odmítni
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// (stejně jako u identityKey), ať se do kontaktů nedostane nesmysl.
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if (deliveryAddress.length != 32) return null;
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}
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return PublicIdentity(
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displayName: map['n'] as String,
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identityKey: identityKey,
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createdAt: DateTime.parse(map['ts'] as String),
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accountId: map['aid'] as String?,
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deliveryAddress: deliveryAddress,
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);
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} catch (_) {
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return null;
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}
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}
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Map<String, dynamic> toJson() => {
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'v': 2,
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'displayName': displayName,
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'identityKey': base64Encode(identityKey),
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'createdAt': createdAt.toIso8601String(),
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'accountId': accountId,
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'deliveryAddress':
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deliveryAddress == null ? null : base64Encode(deliveryAddress!),
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};
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factory PublicIdentity.fromJson(Map<String, dynamic> json) {
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if (json['v'] != 2) {
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throw const FormatException('Unsupported contact format');
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}
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final da = json['deliveryAddress'] as String?;
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return PublicIdentity(
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displayName: json['displayName'] as String,
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identityKey: base64Decode(json['identityKey'] as String),
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createdAt: DateTime.parse(json['createdAt'] as String),
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accountId: json['accountId'] as String?,
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deliveryAddress: da == null ? null : base64Decode(da),
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);
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}
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}
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