internal static bool Decrypt(
DecMPEFileInfo decMpeFileInfo,
string[] passwords,
string outputDir,
IProgress <string> progress = null)
{
int nQuestions = decMpeFileInfo._nQuestions;
int nRequiredPasswords = decMpeFileInfo._nRequiredPasswords;
int nDecryptedQuestionKeys = 0; // Number of QuestionKeys that could be decoded. (J)複号できたQuestionKeyの数
int[] questionKeyIndexes = new int[nRequiredPasswords]; // Index of QuestionKeys that could be decoded. (J)複号できたQuestionKeyのIndex
byte[] questionKeys = new byte[nRequiredPasswords * Crypto.AES_KEY_SIZE_BYTE]; // Combined Question Key (for decrypt dataKey)
// check password
for (int i = 0; i < nQuestions && nDecryptedQuestionKeys < nRequiredPasswords; ++i)
{
var passwordTxt = passwords[i];
if (passwordTxt == "")
{
continue;
}
var question = decMpeFileInfo._decQuestions[i];
byte[] password = Encoding.UTF8.GetBytes(passwordTxt);
for (int j = 0; j < question.nPasswords; ++j)
{
var result = Crypto.decryptByte(question.encryptedQuestionKeys, j * Crypto.AES_KEY_SIZE_BYTE_WITH_PADDING, Crypto.AES_KEY_SIZE_BYTE_WITH_PADDING, password, Crypto.createSalt(i, j));
if (result != null)
{
if (result.Length != Crypto.AES_KEY_SIZE_BYTE)
{ // assertion
throw new Exception("broken file");
}
// store question key
Buffer.BlockCopy(result, 0, questionKeys, nDecryptedQuestionKeys * Crypto.AES_KEY_SIZE_BYTE, Crypto.AES_KEY_SIZE_BYTE);
questionKeyIndexes[nDecryptedQuestionKeys] = i;
nDecryptedQuestionKeys += 1;
break;
}
}
}
if (nDecryptedQuestionKeys < nRequiredPasswords)
{
return(false); // fail. number of passwords is not enough.
}
// decrypt data
byte[] dataKey = null;
int[][] combinaitons = Combination.enumerateCombination(nQuestions, nRequiredPasswords);
for (int i = 0; i < combinaitons.Length; ++i)
{
if (combinaitons[i].SequenceEqual(questionKeyIndexes))
{
dataKey = Crypto.decryptByte(decMpeFileInfo._encryptedDataKeys, i * Crypto.AES_KEY_SIZE_BYTE_WITH_PADDING, Crypto.AES_KEY_SIZE_BYTE_WITH_PADDING, questionKeys);
break;
}
}
if (dataKey == null)
{
throw new Exception("broken file");
}
progress?.Report("(1/3) decripting archive.");
// OK
var tmpFileCompress = System.IO.Path.GetRandomFileName();
try
{
using (FileStream zipFS = new FileStream(tmpFileCompress, FileMode.Create))
{
decMpeFileInfo._encryptedFS.Position = decMpeFileInfo._dataStartPosition;
Crypto.decryptStream(decMpeFileInfo._encryptedFS, zipFS, dataKey);
}
// ZipFile.ExtractToDirectory can not read files unless Close() is done on zipFS
//(J) zipFS を Close() しないと ZipFile.ExtractToDirectory はファイルを読み込めない
try
{
progress?.Report("(2/3) creating output file(s).");
System.IO.Compression.ZipFile.ExtractToDirectory(tmpFileCompress, outputDir);
}
catch (Exception ex)
{
throw ex;
}
}
finally
{
File.Delete(tmpFileCompress);
}
progress?.Report("(3/3) finished.");
return(true); // succeed
}
/**
* encryption
*/
internal static void Encrypt_2(
FileStream encryptedFS,
string[] hintList,
List <string>[] passwordList,
int nRequiredPasswords,
AppConst.MPE_Flag flag,
RNGCryptoServiceProvider r,
byte[] dataKey,
FileStream outputFS,
IProgress <string> progress = null)
{
// generate questionKeys, encryptedQuestionKeys
int nQuestions = hintList.Length;
byte[][] questionKeys = new byte[nQuestions][];
byte[][][] encryptedQuestionKeys = new byte[nQuestions][][];
for (int i = 0; i < nQuestions; ++i)
{
questionKeys[i] = new byte[Crypto.AES_KEY_SIZE_BYTE]; // Encryption key for dataKey
r.GetBytes(questionKeys[i]);
// encrypt questionKey
// Based on the number of passwords, assign the location of the password to encrypt questionKeys. In order to hide the number of passwords, dummy indexes are also included.
// For example, when three passwords are set in the Question being processed, the following values are randomly set in passwordEncryptIndexes.
// passwordEncryptIndexes = {1, -1, 0, 2, -1}
// In this case, encryptedQuestionKeys is [question 0] encrypted questionKey with password 1, [1]: dummy, [2]: questionKey encrypted with password 0, [3]: questionKey encrypted with password 2 , [4]: Dummy is stored.
//(J) パスワードの個数をもとに、questionKeysを暗号化するパスワードの位置を割り当てる。パスワード個数を隠蔽するため、ダミーのインデクスも含まれる。
//(J) たとえば、処理中の Question にパスワードが3つ設定されている場合に、passwordEncryptIndexes には以下のような値をランダムに設定する。
//(J) passwordEncryptIndexes = {1, -1, 0, 2, -1}
//(J) この場合はencryptedQuestionKeys は、[0]:パスワード1で暗号化されたquestionKey, [1]:ダミー, [2]:パスワード0で暗号化されたquestionKey, [3]:パスワード2で暗号化されたquestionKey, [4]:ダミー が格納される。
int[] passwordEncryptIndexes = alllocPasswordEncryptIndexes(passwordList[i].Count);
encryptedQuestionKeys[i] = new byte[passwordEncryptIndexes.Length][];
for (int j = 0; j < passwordEncryptIndexes.Length; ++j)
{
if (passwordEncryptIndexes[j] >= 0)
{ // real password
String password = passwordList[i][passwordEncryptIndexes[j]];
byte[] passwordBytes = Encoding.UTF8.GetBytes(password);
encryptedQuestionKeys[i][j] = Crypto.encryptByte(questionKeys[i], passwordBytes, Crypto.createSalt(i, j));
if (encryptedQuestionKeys[i][j].Length != Crypto.AES_KEY_SIZE_BYTE_WITH_PADDING)
{ // assertion
throw new Exception("system error"); //!
}
}
else
{ // dummy key
byte[] dummyKey = new byte[Crypto.AES_KEY_SIZE_BYTE_WITH_PADDING];
r.GetBytes(dummyKey);
encryptedQuestionKeys[i][j] = dummyKey;
}
}
}
// generate encryptedDataKey
int[][] combinaiton = Combination.enumerateCombination(nQuestions, nRequiredPasswords);
byte[] combinedQuestionKey = new byte[nRequiredPasswords * Crypto.AES_KEY_SIZE_BYTE];
byte[][] encryptedDataKey = new byte[combinaiton.Length][];
for (int i = 0; i < combinaiton.Length; ++i)
{
// Create a password for dataKey from multiple question keys.
//(J) 複数のquestion key から dataKey 用のパスワードを作成する
for (int j = 0; j < combinaiton[i].Length; ++j)
{
int qkIdx = combinaiton[i][j];
Buffer.BlockCopy(questionKeys[qkIdx], 0, combinedQuestionKey, j * Crypto.AES_KEY_SIZE_BYTE, Crypto.AES_KEY_SIZE_BYTE);
}
encryptedDataKey[i] = Crypto.encryptByte(dataKey, combinedQuestionKey);
if (encryptedDataKey[i].Length != Crypto.AES_KEY_SIZE_BYTE_WITH_PADDING)
{ // assertion
throw new Exception("system error"); //!
}
}
progress?.Report("(3/4) creating output file.");
// create question Header (for MPE File)
using (var questionHeaderMS = new MemoryStream())
{
byte[] bytes;
// flag 1
questionHeaderMS.WriteByte((byte)flag);
// nQuestions 4
bytes = BitConverter.GetBytes(IPAddress.HostToNetworkOrder(nQuestions));
questionHeaderMS.Write(bytes, 0, bytes.Length);
// nRequiredPasswords 4
bytes = BitConverter.GetBytes(IPAddress.HostToNetworkOrder(nRequiredPasswords));
questionHeaderMS.Write(bytes, 0, bytes.Length);
// nPasswordCombinations 4
bytes = BitConverter.GetBytes(IPAddress.HostToNetworkOrder(encryptedDataKey.Length));
questionHeaderMS.Write(bytes, 0, bytes.Length);
// encryptedDataKeys n * 48
for (int i = 0; i < encryptedDataKey.Length; ++i)
{
questionHeaderMS.Write(encryptedDataKey[i], 0, encryptedDataKey[i].Length);
}
// Question n
for (int i = 0; i < nQuestions; ++i)
{
// hint string len 4
byte[] hintStrBytes = Encoding.UTF8.GetBytes(hintList[i]);
bytes = BitConverter.GetBytes(IPAddress.HostToNetworkOrder(hintStrBytes.Length));
questionHeaderMS.Write(bytes, 0, bytes.Length);
// hint string n
questionHeaderMS.Write(hintStrBytes, 0, hintStrBytes.Length);
// nPasswords 4
bytes = BitConverter.GetBytes(IPAddress.HostToNetworkOrder(encryptedQuestionKeys[i].Length));
questionHeaderMS.Write(bytes, 0, bytes.Length);
// encryptedQuestionKeys n * 48
for (int j = 0; j < encryptedQuestionKeys[i].Length; ++j)
{
questionHeaderMS.Write(encryptedQuestionKeys[i][j], 0, encryptedQuestionKeys[i][j].Length);
}
}
Encrypt_3(questionHeaderMS, encryptedFS, outputFS);
}
}
