[英]C# AES and RSA File Encryption - How to use IV?
我正在編寫一個程序,它可以在以下情況下工作:
據我了解,該協議適合我的用例。
我遇到的問題是用 C# 編碼。 我遇到了 AES 加密需要初始化向量 (IV) 的情況,我嘗試通過在兩者上使用公共 RSA 密鑰來將其與 AES 密鑰一起加密。 但是 512(2 * 256) 大小比 RSA 樂於加密的要大。 所以我想,既然我每次都像 AES 密鑰一樣隨機創建初始化向量,我可以將 IV 添加到 AES 密文的前面。 但是,我不確定在我的函數中執行此操作的代碼的位置
任何對“協議”或其他將 IV 寫入密文的方法的正確方向的幫助都會很棒。 先感謝您。
static public Tuple<byte[], byte[]> EncryptAES(byte[] toEncryptAES, RSAParameters RSAPublicKey)
{
byte[] encryptedAES = null;
byte[] encryptedRSA = null;
using (MemoryStream ms = new MemoryStream())
{
using (RijndaelManaged AES = new RijndaelManaged())
{
AES.KeySize = 256;
AES.BlockSize = 128;
AES.Mode = CipherMode.CBC;
AES.GenerateIV();
AES.GenerateKey();
encryptedRSA = RSAEncrypt(AES.Key, RSAPublicKey);
using (var cs = new CryptoStream(ms, AES.CreateEncryptor(), CryptoStreamMode.Write))
{
ms.Write(AES.IV, 0, AES.KeySize); //DOESNT WORK HERE
//Can't use CS to write it to the stream else it will encrypt along with file
cs.Write(toEncryptAES, 0, toEncryptAES.Length);
cs.Close();
}
encryptedAES = ms.ToArray();
}
}
return new Tuple<byte[], byte[]>(encryptedAES, encryptedRSA);
}
static public byte[] DecryptAES(byte[] toDecryptAES, byte[] AESKeyAndIV, RSAParameters RSAPrivateKey)
{
byte[] AESKey = RSADecrypt(AESKeyAndIV, RSAPrivateKey);
using (MemoryStream ms = new MemoryStream())
{
using (RijndaelManaged AES = new RijndaelManaged())
{
AES.KeySize = 256;
AES.BlockSize = 128;
AES.Key = AESKey;
ms.Read(AES.IV, 0, AES.KeySize); //Not sure if can read MS here
AES.Mode = CipherMode.CBC;
using (var cs = new CryptoStream(ms, AES.CreateDecryptor(), CryptoStreamMode.Write))
{
//Would I need to move 0 to 256?
cs.Write(toDecryptAES, 0, toDecryptAES.Length);
cs.Close();
}
return ms.ToArray();
}
}
}
您非常接近,請在創建 CryptoStream 之前寫出 IV
static public Tuple<byte[], byte[]> EncryptAES(byte[] toEncryptAES, RSAParameters RSAPublicKey)
{
byte[] encryptedAES = null;
byte[] encryptedRSA = null;
using (MemoryStream ms = new MemoryStream())
{
using (RijndaelManaged AES = new RijndaelManaged())
{
AES.KeySize = 256;
AES.BlockSize = 128;
AES.Mode = CipherMode.CBC;
AES.GenerateIV();
AES.GenerateKey();
encryptedRSA = RSAEncrypt(AES.Key, RSAPublicKey);
ms.Write(AES.IV, 0, AES.KeySize); //Move the write here.
using (var cs = new CryptoStream(ms, AES.CreateEncryptor(), CryptoStreamMode.Write))
{
cs.Write(toEncryptAES, 0, toEncryptAES.Length);
cs.Close();
}
encryptedAES = ms.ToArray();
}
}
return new Tuple<byte[], byte[]>(encryptedAES, encryptedRSA);
}
對於解密,請確保循環讀取直到您完全讀取了 IV 的 byte[], Stream.Read
不能保證讀取您要求它讀取的所有字節。 我通常會創建一個靜態方法ReadFully
來確保讀取所有字節。
private static byte[] ReadFully(Stream stream, int length)
{
int offset = 0;
byte[] buffer = new byte[length];
while(offset < length)
{
offset += stream.Read(buffer, offset, length - offset);
}
return buffer;
}
然后只需使用該方法讀取IV。 您還想使用cs.Read
而不是cs.Write
來讀出加密數據並將流置於讀取模式,但是使用.CopyTo
並將數據復制到新的 MemoryStream 會更容易。
static public byte[] DecryptAES(byte[] toDecryptAES, byte[] AESKeyAndIV, RSAParameters RSAPrivateKey)
{
byte[] AESKey = RSADecrypt(AESKeyAndIV, RSAPrivateKey);
using (MemoryStream source = new MemoryStream(toDecryptAES))
{
using (RijndaelManaged AES = new RijndaelManaged())
{
AES.KeySize = 256;
AES.BlockSize = 128;
AES.Key = AESKey;
var iv = ReadFully(source, AES.KeySize);
AES.IV = iv;
AES.Mode = CipherMode.CBC;
using (var cs = new CryptoStream(source, AES.CreateDecryptor(), CryptoStreamMode.Read))
{
using(var dest = new MemoryStream())
{
cs.CopyTo(dest);
return dest.ToArray();
}
}
}
}
}
對於其他讀者,請注意RSAEncrypt
和RSADecrypt
是調用RSACryptoServiceProvider
包裝器。
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