ファイルを暗号化するライブラリを自作してみました。
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namespace NamespaceEncodeFiles { public class EncodeFiles { private const int KEY_SIZE = 256; private const int BLOCK_SIZE = 128; private const int BUFFER_SIZE = BLOCK_SIZE * 32; // バッファーサイズはBlockSizeの倍数にする private const int SALT_SIZE = 16; // 8以上 static private byte[] GetSalt() { Point pt = Control.MousePosition; long nowTicks = DateTime.Now.Ticks; string str = String.Format("{0}{1}{2}", nowTicks, pt.X, pt.Y); Rfc2898DeriveBytes deriveBytes = new Rfc2898DeriveBytes(str, SALT_SIZE); return deriveBytes.Salt; } //パスワードから暗号キーを作成する static private byte[] GetKeyFromPassword(string password, byte[] salt) { //Rfc2898DeriveBytesオブジェクトを作成する Rfc2898DeriveBytes deriveBytes = new Rfc2898DeriveBytes(password, salt); //反復処理回数を指定する 1000回 deriveBytes.IterationCount = 1000; //キーを生成する return deriveBytes.GetBytes(KEY_SIZE / 8); // KEY_SIZEはビット数なので8で割る } // 前処理用のソルト static private byte[] GetAnotherSalt() { long nowTicks = DateTime.Now.Ticks; Rfc2898DeriveBytes deriveBytes = new Rfc2898DeriveBytes(nowTicks.ToString(), SALT_SIZE); return deriveBytes.Salt; } //パスワードから前処理用の暗号キーを作成する static private byte[] GetAnotherKeyFromPassword(string password, byte[] salt) { //Rfc2898DeriveBytesオブジェクトを作成する Rfc2898DeriveBytes deriveBytes = new Rfc2898DeriveBytes(password, salt); //反復処理回数を指定する 1000回 deriveBytes.IterationCount = 1000; //キーを生成する return deriveBytes.GetBytes(BUFFER_SIZE); } //パスワードから初期化ベクトルを作成する static private byte[] GetIVFromPassword(string password) { Rfc2898DeriveBytes deriveBytes = new Rfc2898DeriveBytes(password, GetSalt()); //反復処理回数を不定にする 1000回＋α deriveBytes.IterationCount = 1000 + DateTime.Now.Millisecond; return deriveBytes.GetBytes(BLOCK_SIZE / 8); } static byte[] GetEncodeFileInfo(string srcFilePath, byte[] key) { // ファイル情報を取得する FileInfo info = new FileInfo(srcFilePath); long creationTime = info.CreationTime.Ticks; long lastAccessTime = info.LastAccessTime.Ticks; long lastWriteTime = info.LastWriteTime.Ticks; string name = info.Name; byte[] vs = Encoding.UTF8.GetBytes(name); int len = vs.Length; // ファイル情報を書き込む MemoryStream ms = new MemoryStream(); ms.Write(BitConverter.GetBytes(creationTime), 0, sizeof(long)); ms.Write(BitConverter.GetBytes(lastAccessTime), 0, sizeof(long)); ms.Write(BitConverter.GetBytes(lastWriteTime), 0, sizeof(long)); ms.Write(BitConverter.GetBytes(len), 0, sizeof(int)); ms.Write(vs, 0, len); byte[] fileInfoBuf = ms.ToArray(); for(int i = 0; i < fileInfoBuf.Length; i++) fileInfoBuf[i] ^= key[i]; return fileInfoBuf; } static public void EncodeFile(string srcFilePath, string destFilePath, string password) { // Saltを生成する byte[] salt = GetSalt(); byte[] key = GetKeyFromPassword(password, salt); byte[] iv = GetIVFromPassword(password); using(AesManaged aes = new AesManaged()) { // AESインスタンスのパラメータ設定 aes.KeySize = KEY_SIZE; aes.BlockSize = BLOCK_SIZE; aes.Mode = CipherMode.CBC; aes.Key = key; aes.IV = iv; aes.Padding = PaddingMode.ISO10126; // 暗号化オブジェクト生成 ICryptoTransform ct = aes.CreateEncryptor(aes.Key, aes.IV); // 出力ファイルストリーム using(FileStream outFileStream = new FileStream(destFilePath, FileMode.Create, FileAccess.Write)) { // Saltの書き込み outFileStream.Write(salt, 0, SALT_SIZE); // 初期化ベクトル 書き込み outFileStream.Write(aes.IV, 0, BLOCK_SIZE / 8); using(CryptoStream cryptoStream = new CryptoStream(outFileStream, ct, CryptoStreamMode.Write)) { using(FileStream inFileStream = new FileStream(srcFilePath, FileMode.Open, FileAccess.Read)) { byte[] anotherSolt = GetAnotherSalt(); byte[] anotherKey = GetAnotherKeyFromPassword(password, anotherSolt); cryptoStream.Write(anotherSolt, 0, anotherSolt.Length); // ファイル情報を暗号化して書き込む byte[] fileInfoBuf = GetEncodeFileInfo(srcFilePath, anotherKey); cryptoStream.Write(fileInfoBuf, 0, fileInfoBuf.Length); byte[] buf = new byte[BUFFER_SIZE]; while(true) { int size = inFileStream.Read(buf, 0, buf.Length); // ストリーム暗号で一旦暗号化 for(int i = 0; i < size; i++) buf[i] ^= anotherKey[i]; if(size == 0) break; // 出力ファイルへ書き込み（AESで暗号化される） cryptoStream.Write(buf, 0, size); } } } } } } public class DecodeFileInfo { public long CreationTime = 0; public long LastAccessTime = 0; public long LastWriteTime = 0; public string FileName = ""; } static DecodeFileInfo GetDeccodeFileInfo(CryptoStream cryptoStream, byte[] key) { DecodeFileInfo decodeFileInfo = new DecodeFileInfo(); MemoryStream ms = new MemoryStream(); // ファイル情報部分を読み込む byte[] longbs = new byte[sizeof(long)]; byte[] intbs = new byte[sizeof(int)]; int readByte = 0; // CryptoStreamからの読み出し // CreationTime readByte += cryptoStream.Read(longbs, 0, sizeof(long)); ms.Write(longbs, 0, sizeof(long)); // LastAccessTime readByte += cryptoStream.Read(longbs, 0, sizeof(long)); ms.Write(longbs, 0, sizeof(long)); // LastWriteTime readByte += cryptoStream.Read(longbs, 0, sizeof(long)); ms.Write(longbs, 0, sizeof(long)); // ファイル名の長さ readByte += cryptoStream.Read(intbs, 0, sizeof(int)); ms.Write(intbs, 0, sizeof(int)); // 読み出したデータを復号 byte[] fileInfoBuf = ms.ToArray(); for(int i = 0; i < fileInfoBuf.Length; i++) fileInfoBuf[i] ^= key[i]; ms = new MemoryStream(fileInfoBuf); ms.Read(longbs, 0, sizeof(long)); decodeFileInfo.CreationTime = BitConverter.ToInt64(longbs, 0); ms.Read(longbs, 0, sizeof(long)); decodeFileInfo.LastAccessTime = BitConverter.ToInt64(longbs, 0); ms.Read(longbs, 0, sizeof(long)); decodeFileInfo.LastWriteTime = BitConverter.ToInt64(longbs, 0); ms.Read(intbs, 0, sizeof(int)); int len = BitConverter.ToInt32(intbs, 0); // ファイル名はここで復号する byte[] vs = new byte[len]; cryptoStream.Read(vs, 0, len); ms = new MemoryStream(vs); byte[] fileName = ms.ToArray(); for(int i = 0; i < fileName.Length; i++) fileName[i] ^= key[i + readByte]; decodeFileInfo.FileName = Encoding.UTF8.GetString(fileName); return decodeFileInfo; } static public bool DecodeFile(string srcFilePath, string destFolderPath, string password) { try { DecodeFile2(srcFilePath, destFolderPath, password); return true; } catch { return false; } } static void DecodeFile2(string srcFilePath, string destFolderPath, string password) { using(AesManaged aes = new AesManaged()) { // AESインスタンスのパラメータ設定 aes.KeySize = KEY_SIZE; aes.BlockSize = BLOCK_SIZE; aes.Mode = CipherMode.CBC; aes.Padding = PaddingMode.ISO10126; using(FileStream inFileStream = new FileStream(srcFilePath, FileMode.Open, FileAccess.Read)) { // Saltを読み込む byte[] salt = GetSalt(); inFileStream.Read(salt, 0, SALT_SIZE); byte[] key = GetKeyFromPassword(password, salt); aes.Key = key; // 初期化ベクトル読込 byte[] iv = new byte[BLOCK_SIZE / 8]; inFileStream.Read(iv, 0, iv.Length); aes.IV = iv; // 復号化オブジェクト生成 ICryptoTransform ct = aes.CreateDecryptor(aes.Key, aes.IV); using(CryptoStream cryptoStream = new CryptoStream(inFileStream, ct, CryptoStreamMode.Read)) { if(!Directory.Exists(destFolderPath)) Directory.CreateDirectory(destFolderPath); string tempFilePath = destFolderPath + "\\temp.temp"; string destFilePath = ""; DecodeFileInfo info1 = null; using(FileStream outFs = new FileStream(tempFilePath, FileMode.Create, FileAccess.Write)) { byte[] anotherSolt = new byte[SALT_SIZE]; cryptoStream.Read(anotherSolt, 0, SALT_SIZE); byte[] anotherKey = GetAnotherKeyFromPassword(password, anotherSolt); // ファイル情報部分を読み込む info1 = GetDeccodeFileInfo(cryptoStream, anotherKey); destFilePath = destFolderPath + "\\" + info1.FileName; if(File.Exists(destFilePath)) { MessageBox.Show("復号しようとしているファイルと同名のファイルがあるので処理ができません。"); return; } byte[] buf = new byte[BUFFER_SIZE]; while(true) { int size = cryptoStream.Read(buf, 0, buf.Length); for(int i = 0; i < size; i++) buf[i] ^= anotherKey[i]; if(size == 0) break; outFs.Write(buf, 0, size); } } // ファイル情報を復元する File.Move(tempFilePath, destFilePath); FileInfo info = new FileInfo(destFilePath); info.CreationTime = new DateTime(info1.CreationTime); info.LastAccessTime = new DateTime(info1.LastAccessTime); info.LastWriteTime = new DateTime(info1.LastWriteTime); } } } } } } |
