36 lines
915 B
Dart
36 lines
915 B
Dart
import 'dart:convert';
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import 'package:cryptography/cryptography.dart';
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/// Info string for KDF_RK
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const kdfRkInfoString = 'OMEMO Root Chain';
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/// Flags for KDF_CK
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const kdfCkNextMessageKey = 0x01;
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const kdfCkNextChainKey = 0x02;
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/// Signals KDF_CK function as specified by OMEMO 0.8.3.
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Future<List<int>> kdfCk(List<int> ck, int constant) async {
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final hkdf = Hkdf(hmac: Hmac(Sha256()), outputLength: 32);
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final result = await hkdf.deriveKey(
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secretKey: SecretKey(ck),
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nonce: [constant],
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);
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return result.extractBytes();
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}
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/// Signals KDF_RK function as specified by OMEMO 0.8.3.
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Future<List<int>> kdfRk(List<int> rk, List<int> dhOut) async {
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final algorithm = Hkdf(
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hmac: Hmac(Sha256()),
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outputLength: 32,
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);
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final result = await algorithm.deriveKey(
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secretKey: SecretKey(dhOut),
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nonce: rk,
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info: utf8.encode(kdfRkInfoString),
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);
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return result.extractBytes();
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}
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