public byte[] TransformRaw(byte[] buffer, int outputLength)
{
if (buffer == null)
{
throw new ArgumentNullException("buffer");
}
IAsymmetricBlockCipher cipher = new RsaEngine();
cipher.Init(true, Key);
if (outputLength > cipher.GetOutputBlockSize())
{
throw new ArgumentOutOfRangeException(nameof(outputLength), "Too large output length");
}
byte[] transformed = TransformInternal(buffer, cipher);
if (transformed.Length == outputLength)
{
return(transformed);
}
byte[] truncated = new byte[outputLength];
Array.Copy(transformed, transformed.Length - outputLength, truncated, 0, outputLength);
return(truncated);
}
public static MemoryStream DecryptRsa(Stream inputStream, string pemKey)
{
AsymmetricKeyParameter keyParameter = ReadPem(pemKey);
var engine = new RsaEngine();
engine.Init(false, keyParameter);
var outputStream = new MemoryStream();
int inputBlockSize = engine.GetInputBlockSize();
int outputBlockSize = engine.GetOutputBlockSize();
byte[] inputBlock = new byte[inputBlockSize];
while (inputStream.Read(inputBlock, 0, inputBlock.Length) > 0)
{
byte[] outputBlock = engine.ProcessBlock(inputBlock, 0, inputBlockSize);
int requiredPadding = outputBlockSize - outputBlock.Length;
if (requiredPadding > 0)
{
byte[] paddedOutputBlock = new byte[outputBlockSize];
outputBlock.CopyTo(paddedOutputBlock, requiredPadding);
outputBlock = paddedOutputBlock;
}
outputStream.Write(outputBlock, 0, outputBlock.Length);
}
outputStream.Seek(0, SeekOrigin.Begin);
return(outputStream);
}
/// <summary>
/// Decrypts a file with a provided decryption key.
/// </summary>
/// <param name="filePath">An encrypted file</param>
/// <param name="key">The RSA key in PEM format</param>
/// <exception cref="ArgumentNullException">When the argument filePath is null</exception>
/// <exception cref="ArgumentNullException">When the argument keyPath is null</exception>
/// <returns>A memory stream with the decrypted file</returns>
public static MemoryStream DecryptRsa(string filePath, string key)
{
if (filePath == null)
{
throw new ArgumentNullException(nameof(filePath));
}
if (key == null)
{
throw new ArgumentNullException(nameof(key));
}
AsymmetricKeyParameter keyParameter = GetKeyOrDefault(key);
RsaEngine engine = new RsaEngine();
engine.Init(false, keyParameter);
MemoryStream outputStream = new MemoryStream();
using (FileStream inputStream = File.OpenRead(filePath))
{
int inputBlockSize = engine.GetInputBlockSize();
int outputBlockSize = engine.GetOutputBlockSize();
byte[] inputBlock = new byte[inputBlockSize];
while (inputStream.Read(inputBlock, 0, inputBlock.Length) > 0)
{
byte[] outputBlock = engine.ProcessBlock(inputBlock, 0, inputBlockSize);
int requiredPadding = outputBlockSize - outputBlock.Length;
if (requiredPadding > 0)
{
byte[] paddedOutputBlock = new byte[outputBlockSize];
outputBlock.CopyTo(paddedOutputBlock, requiredPadding);
outputBlock = paddedOutputBlock;
}
outputStream.Write(outputBlock, 0, outputBlock.Length);
}
}
outputStream.Seek(0, SeekOrigin.Begin);
return(outputStream);
}