public static EncryptedDiaryRecord EncryptRecord(DiaryRecord record, RSACryptoServiceProvider rsa)
{
var rij = Rijndael.Create();
rij.KeySize = 256;
rij.GenerateKey();
rij.GenerateIV();
var encryptedRecord = new EncryptedDiaryRecord();
var header = new MemoryStream();
header.Write(rij.Key, 0, rij.Key.Length);
header.Write(rij.IV, 0, rij.IV.Length);
encryptedRecord.Header = rsa.Encrypt(header.ToArray(), false);
var encryptedBodyStream = new MemoryStream();
using (var body = new CryptoStream(encryptedBodyStream, rij.CreateEncryptor(), CryptoStreamMode.Write))
{
Serializer.Serialize(body, record);
}
encryptedRecord.Body = encryptedBodyStream.ToArray();
return(encryptedRecord);
}
public DiaryRecord ReadPrevious()
{
var reader = new BinaryReader(_fileStream);
_fileStream.Seek(-4, SeekOrigin.Current);
var messageLength = reader.ReadInt32();
_fileStream.Seek(-(messageLength + 4), SeekOrigin.Current);
var recordBytes = reader.ReadBytes(messageLength);
if (recordBytes.Length != messageLength)
{
throw new InvalidDataException("The record could not be read");
}
var encryptedDiaryRecord = new EncryptedDiaryRecord();
var headerLength = _rsa.KeySize / 8;
encryptedDiaryRecord.Header = new byte[headerLength];
encryptedDiaryRecord.Body = new byte[recordBytes.Length - headerLength];
Buffer.BlockCopy(recordBytes, 0, encryptedDiaryRecord.Header, 0, headerLength);
Buffer.BlockCopy(recordBytes, headerLength, encryptedDiaryRecord.Body, 0, encryptedDiaryRecord.Body.Length);
var record = EncryptionHelper.DecryptEntry(encryptedDiaryRecord, _rsa);
_fileStream.Seek(-(messageLength + 4), SeekOrigin.Current);
return(record);
}
public static DiaryRecord DecryptEntry(EncryptedDiaryRecord record, RSACryptoServiceProvider rsa)
{
var decryptedChunk = rsa.Decrypt(record.Header, false);
var key = new byte[32];
var iv = new byte[16];
var rij = Rijndael.Create();
Buffer.BlockCopy(decryptedChunk, 0, key, 0, 32);
Buffer.BlockCopy(decryptedChunk, 32, iv, 0, 16);
using (var cs = new CryptoStream(new MemoryStream(record.Body), rij.CreateDecryptor(key, iv), CryptoStreamMode.Read))
{
return(Serializer.Deserialize <DiaryRecord>(cs));
}
}
