// For AES the method in the entry is 99, and the real compression method is in the extradata // private void ProcessAESExtraData(ZipExtraData extraData) { if (extraData.Find(0x9901)) { // Set version and flag for Zipfile.CreateAndInitDecryptionStream versionToExtract = ZipConstants.VERSION_AES; // Ver 5.1 = AES see "Version" getter // Set StrongEncryption flag for ZipFile.CreateAndInitDecryptionStream Flags = Flags | (int)GeneralBitFlags.StrongEncryption; // // Unpack AES extra data field see http://www.winzip.com/aes_info.htm int length = extraData.ValueLength; // Data size currently 7 if (length < 7) { throw new ZipException("AES Extra Data Length " + length + " invalid."); } int ver = extraData.ReadShort(); // Version number (1=AE-1 2=AE-2) int vendorId = extraData.ReadShort(); // 2-character vendor ID 0x4541 = "AE" int encrStrength = extraData.ReadByte(); // encryption strength 1 = 128 2 = 192 3 = 256 int actualCompress = extraData.ReadShort(); // The actual compression method used to compress the file _aesVer = ver; _aesEncryptionStrength = encrStrength; method = (CompressionMethod)actualCompress; } else { throw new ZipException("AES Extra Data missing"); } }