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AES key length is not equal to AES block size #47

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15b854d
Fixed keylength in pace
Jul 23, 2025
383eb00
Added a unit test
Jul 23, 2025
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6 changes: 3 additions & 3 deletions lib/src/proto/pace.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -544,7 +544,7 @@ class PACE {

if (cipherAlgorithm == CipherAlgorithm.AES) {
_log.debug("Cipher algorithm: AES.");
AESCipher aesCipher = AESChiperSelector.getChiper(size: KEY_LENGTH.s128); //size is not important
AESCipher aesCipher = AESChiperSelector.getChiper(size: keyLength);
Uint8List computedAuthToken = aesCipher.calculateCMAC(data: inputData, key: macKey);
_log.sdVerbose("Computed auth token: ${computedAuthToken.hex()}");
return computedAuthToken;
Expand Down Expand Up @@ -580,8 +580,8 @@ class PACE {

if (cipherAlgo == CipherAlgorithm.AES){
_log.debug("PACE.decryptNonce; Cipher algorithm: AES");
AESCipher aesCipher128 = AESChiperSelector.getChiper(size: KEY_LENGTH.s128);
Uint8List decryptedNonce = aesCipher128.decrypt(data: nonce, key: k_pi);
AESCipher aesCipher = AESChiperSelector.getChiper(size: keyLength);
Uint8List decryptedNonce = aesCipher.decrypt(data: nonce, key: k_pi);
_log.sdVerbose("PACE.decryptNonce; Decrypted nonce: ${decryptedNonce.hex()}");
return decryptedNonce;
}
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45 changes: 45 additions & 0 deletions test/pace_aes_256_test.dart
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Original file line number Diff line number Diff line change
@@ -0,0 +1,45 @@
import 'dart:typed_data';

import 'package:test/test.dart';
import 'package:dmrtd/extensions.dart';

import 'package:dmrtd/src/proto/pace.dart';
import 'package:dmrtd/src/lds/asn1ObjectIdentifiers.dart';
import 'package:dmrtd/src/proto/access_key.dart';
import 'package:dmrtd/src/crypto/aes.dart';

class _DummyAccessKey extends AccessKey {
@override
int PACE_REF_KEY_TAG = 0x00;

final Uint8List _kpi;
_DummyAccessKey(this._kpi);

@override
Uint8List Kpi(CipherAlgorithm cipherAlgorithm, KEY_LENGTH keyLength) => _kpi;

@override
String toString() => 'DummyAccessKey{Kpi:${_kpi.hex()}}';
}

void main() {
test('decryptNonce accepts AES key length different from block size', () {
final paceProtocolMap = customOIDS.firstWhere(
(e) => e['readableName'] == 'id-PACE-ECDH-GM-AES-CBC-CMAC-256');
final paceProtocol = OIEPaceProtocol.fromMap(item: paceProtocolMap);

final kpi =
'00112233445566778899AABBCCDDEEFF00112233445566778899AABBCCDDEEFF'
.parseHex();
final nonce = 'A1A2A3A4A5A6A7A8A9AAABACADAEAFB0'.parseHex();

final aes = AESChiperSelector.getChiper(size: KEY_LENGTH.s256);
final encrypted = aes.encrypt(data: nonce, key: kpi);

final accessKey = _DummyAccessKey(kpi);
final decrypted = PACE.decryptNonce(
paceProtocol: paceProtocol, nonce: encrypted, accessKey: accessKey);

expect(decrypted, nonce);
});
}