[英]C# AES and RSA File Encryption - How to use IV?
我正在编写一个程序,它可以在以下情况下工作:
据我了解,该协议适合我的用例。
我遇到的问题是用 C# 编码。 我遇到了 AES 加密需要初始化向量 (IV) 的情况,我尝试通过在两者上使用公共 RSA 密钥来将其与 AES 密钥一起加密。 但是 512(2 * 256) 大小比 RSA 乐于加密的要大。 所以我想,既然我每次都像 AES 密钥一样随机创建初始化向量,我可以将 IV 添加到 AES 密文的前面。 但是,我不确定在我的函数中执行此操作的代码的位置
任何对“协议”或其他将 IV 写入密文的方法的正确方向的帮助都会很棒。 先感谢您。
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,请在创建 CryptoStream 之前写出 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);
}
对于解密,请确保循环读取直到您完全读取了 IV 的 byte[], Stream.Read
不能保证读取您要求它读取的所有字节。 我通常会创建一个静态方法ReadFully
来确保读取所有字节。
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;
}
然后只需使用该方法读取IV。 您还想使用cs.Read
而不是cs.Write
来读出加密数据并将流置于读取模式,但是使用.CopyTo
并将数据复制到新的 MemoryStream 会更容易。
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();
}
}
}
}
}
对于其他读者,请注意RSAEncrypt
和RSADecrypt
是调用RSACryptoServiceProvider
包装器。
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