I am trying to port the following code from C# into Java. I have made multiple attempts to try and decrypt my encrypted data and I get gibberish every time. The code below uses the org.bouncycastle library and unfortunately there doesn't seem to be a 1-1 mapping between the C# code and the Java code.
I basically know three things:
byte[] file - This contains my encrypted file. Usually a pretty large array of bytes.
byte[] padding - It is 32*bytes* every time and it seems that the first 16 bytes of this are used as the IV.
byte[] aesKey - It is 32*bytes* every time and I do not know how exactly the C# code is using this array.
Original C# Code
private byte[] decryptmessage(byte[] cmessage, byte[] iVector, byte[] m_Key)
{
{
//// randomly generated number acts as inetialization vector
m_IV = new byte[16];
Array.Copy(iVector, 0, m_IV, 0, 16);
// GenerateAESKey();
KeyParameter aesKeyParam = ParameterUtilities.CreateKeyParameter("AES", m_Key);
ParametersWithIV aesIVKeyParam = new ParametersWithIV(aesKeyParam, m_IV);
IBufferedCipher cipher = CipherUtilities.GetCipher("AES/CFB/NoPadding");
cipher.Init(false, aesIVKeyParam);
return cipher.DoFinal(cmessage);
}
}
My attempt in Java
private static byte[] decryptMessage(byte[] file, byte[] iVector, byte[] aesKey) throws Exception {
IvParameterSpec spec = new IvParameterSpec(Arrays.copyOfRange(iVector, 0, 16));
SecretKeySpec key = new SecretKeySpec(Arrays.copyOfRange(aesKey, 0, 16), "AES");
Cipher cipher = Cipher.getInstance("AES/CFB/NoPadding");
cipher.init(Cipher.DECRYPT_MODE, key, spec);
return cipher.doFinal(file);
}
P.S: This is the final step of decryption. Before all this I had to take out some initial set of bytes from my encrypted file and decrypt them using an RSA private key to get this AES key.
If someone has a link / document I can read that properly explains the whole process of using AES to encrypt a file, then using RSA on the key and iv to the begining of the encrypted file, I will be extremely happy. I have just been staring at the C# code, I'd like to see something with pictures.
EDIT: Bytes not bits.
EDIT2: Renamed padding to iVector for consistency and correctness.
In the C# code, you initialize the key with 256 bits (32 bytes) and thus get AES-256. In the Java code, you only use 128 bit (16 bytes) and get AES-128.
So the fix is probably:
SecretKeySpec key = new SecretKeySpec(aesKey, "AES");
You might then find that Java doesn't want to use 256 bit keys (for legal reason). You then have to intall the Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files 6.
Related
I am getting an error decrypting a message in go that was encrypted in C# (using corresponding public/private keys)
My client is written in C# and my server is written in Go. I generated a private and public key via go's crypto/rsa package (using rsa.GenerateKey(random Reader, bits int)). I then store the public key file generated where the client can access it and the private key where the server can access it. I encrypt on the client with the following code (using bouncy castle):
public static string Encrypt(string plainText)
{
byte[] plainTextBytes = Encoding.UTF8.GetBytes(plainText);
PemReader pr = new PemReader(
new StringReader(m_publicKey)
);
RsaKeyParameters keys = (RsaKeyParameters)pr.ReadObject();
// PKCS1 OAEP paddings
OaepEncoding eng = new OaepEncoding(new RsaEngine());
eng.Init(true, keys);
int length = plainTextBytes.Length;
int blockSize = eng.GetInputBlockSize();
List<byte> cipherTextBytes = new List<byte>();
for (int chunkPosition = 0; chunkPosition < length; chunkPosition += blockSize)
{
int chunkSize = Math.Min(blockSize, length - chunkPosition);
cipherTextBytes.AddRange(eng.ProcessBlock(
plainTextBytes, chunkPosition, chunkSize
));
}
return Convert.ToBase64String(cipherTextBytes.ToArray());
}
The go server parses this string from the header and uses the private key to decrypt:
func DecryptWithPrivateKey(ciphertext []byte, priv *rsa.PrivateKey) []byte {
hash := sha512.New()
plaintext, err := rsa.DecryptOAEP(hash, rand.Reader, priv, ciphertext, nil)
if err != nil {
fmt.Fprintf(os.Stderr, err.Error())
}
return plaintext
}
The decryption function throws crypto/rsa: decryption error. If I try pasting the cipher text directly into go (rather then sending from the client), the same error occurs.
NOTE: in order to get the public key to load, I needed to change the header from:
-----BEGIN RSA PUBLIC KEY-----
...
to
-----BEGIN PUBLIC KEY-----
...
and the same for the footer. I am assuming this is a formatting issue but not sure how to go about solving.
EDIT: it seems that golang OAEP uses sha256 and bouncy castle uses SHA-1. Go's documentation specifies that the hash for encryption and decryption must be the same. This seems likely to be the issue? If it is, how can I change the hashing algorithm used by either go or C#?
Yes, you need to match the hash. In GoLang you've already set it to SHA-512 if I take a look at your code. Using SHA-256 at minimum should probably be preferred, but using SHA-1 is relatively safe as the MGF1 function doesn't rely on the collision resistance of the underlying hash. It's also the default for most runtimes, I don't know why GoLang decided against that.
Probably the best is to set SHA-512 for both runtimes, so here is the necessary constant for .NET.
Note that the underlying story is even more complex as OAEP uses a hash over a label as well as a hash within MGF1 (mask generation function 1, the only one specified). Both need to be specified in advance and generally the same hash function is used, but sometimes it is not.
The label is generally empty and most runtimes don't even allow setting it, so the hash value over the label is basically a hash-function specific constant that doesn't matter for security. The constant just manages to make things incompatible; "More flexible" isn't always a good thing.
I'm trying to implement Blowfish encryption, ECB mode, through BouncyCastle. The problem is that this code encrypts only first 8 bytes of the file. I don't know, what the problem might be. I've worked with BouncyCastle before.
I found that I'm not the one having this problem, but the solution here didn't help:
Blowfish ECB Mode in BouncyCastle
The code is:
byte[] fileIn = File.ReadAllBytes("file.txt"), fileOut = new byte[fileIn.Length];
BlowfishEngine blowfishEngine = new BlowfishEngine();
blowfishEngine.Init(true, new KeyParameter(Encoding.UTF8.GetBytes("ahoi")));
blowfishEngine.ProcessBlock(fileIn, 0, fileOut, 0);
File.WriteAllBytes("file2.txt", fileOut);
I've been working on this for a while and I don't know much about either PHP or C#. We are building an application that is using AES 128 CBC mode encryption to store things in the database. One part is PHP and JS, the other is C# .NET WPF.
The person who wrote the PHP used the Mcrypt library to crypt/decrypt. I'm using the Chilkat library to encrypt/decrypt. Chilkat had a default C# example that is supposed to mimic the PHP Mcrypt.
Currently I can symmetrically encrypt/decrypt things on .Net, and .Net can decrypt anything from PHP. However the PHP side cannot decrypt anything that I encrypt to the database from the .Net side.
I've narrowed at least part of down to encoding issues, but I'm not sure how to fix it. The decryption scheme on PHP side usually decrypts to ASCII, but for things that I send it decrypts to UTF-8. I've tried to decrypt it then encode from UTF-8 to ASCII to no avail.
I'll show you the in/outputs and the functions. The IV is being set to 16 ASCII 0s to help my debugging along even though it shouldn't really matter.
input from .Net to mcrypt_encrypt func: string "1220"
output: 3tRIG7qUxUsU7WoXDybRRcdQRobOfeFGtQ438V7XRD8=
Parameter input into database = 'same as above'
input of PHP side decrypt func = 3tRIG7qUxUsU7WoXDybRRcdQRobOfeFGtQ438V7XRD8= 'same as above'
output of the mcrypt_decrypt function = ��J���{$�Z'?�u 'iconv says utf-8 encoding'
Ask for anything else and I'll get it if it would help. I'm sure this is some stupid easy problem I can't see.
PHP side - if it matters the PHP charset is set to UTF-8
function encrypt($input)
{
$this->iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC);
/*No longer using random iv :(
$this->iv = mcrypt_create_iv($this->iv_size, MCRYPT_RAND);*/
//use 16 zeros
$this->iv = '0000000000000000';
$encrypted = $this->iv .mcrypt_encrypt(MCRYPT_RIJNDAEL_128, KEY, $input, MODE, $this->iv);
//Finally encode this as base 64, see http://php.net/manual/en/function.base64-encode.php
$encrypted = base64_encode($encrypted);
return $encrypted;
}
function decrypt($input)
{
/*Get our message back!!!
First decode the base 64 string. Note, de/encoding bas 64 != encryption*/
$ciphertext_dec = base64_decode($input);
//Get the iv back out for decryption
$iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC);
//$iv_dec = substr($ciphertext_dec, 0, $iv_size);*/
$iv_dec = '0000000000000000';
//Now get the text of encrypted message (all but the iv in front)
$ciphertext_dec = substr($ciphertext_dec, $iv_size);
//Now decrypt the message
$plaintext_dec = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, KEY, $ciphertext_dec, MCRYPT_MODE_CBC, $iv_dec);
//Test
//test
//$plaintext_dec = iconv("UTF-8", "ASCII", $plaintext_dec);
//echo mb_detect_encoding($plaintext_dec, "auto");
//echo $plaintext_dec;
/*However, we might now have blank space # end of output b/c
remember we de/encrypt via block, so a 10 char long message
could be padded to 16 char long with blank spaces. Get rid of those.*/
$plaintext_dec = trim($plaintext_dec);
//return so we can compare to, i.e., original input
return $plaintext_dec;
}
.NET C#
public string mcrypt_encrypt(string plainText)
{
plainText = Encoding.ASCII.GetString(crypt.IV) + plainText;
byte[] myText = Encoding.ASCII.GetBytes(plainText);
// Do 128-bit AES encryption:
byte[] cipherText = crypt.EncryptBytes(myText);
return Convert.ToBase64String(cipherText);
}
public string mcrypt_decrypt(string cipher_text)
{
byte[] cipher_dec = Convert.FromBase64String(cipher_text);
byte[] plainBytes = crypt.DecryptBytes(cipher_dec);
string decrypted = Encoding.ASCII.GetString(plainBytes);
string plain_text = decrypted.Substring(16, decrypted.Length - 16);
return plain_text.TrimEnd('\0');
}
C# Chilkat init:
// AES is also known as Rijndael.
crypt.CryptAlgorithm = "aes";
// CipherMode may be "ecb" or "cbc"
crypt.CipherMode = "cbc";
// KeyLength may be 128, 192, 256
crypt.KeyLength = 128;
// Pad with NULL bytes (PHP pads with NULL bytes)
crypt.PaddingScheme = 3;
// EncodingMode specifies the encoding of the output for
// encryption, and the input for decryption.
// It may be "hex", "url", "base64", or "quoted-printable".
crypt.EncodingMode = "hex";
// The secret key must equal the size of the key. For
// 256-bit encryption, the binary secret key is 32 bytes.
// For 128-bit encryption, the binary secret key is 16 bytes.
string keyAscii = #"&=*FS6wksG#Zs3qG";
crypt.SecretKey = Encoding.UTF8.GetBytes(keyAscii);
crypt.Charset = "ASCII";
crypt.SetEncodedIV("\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", "ascii");
You have a variety of different problems here. The issue causing the problem you seeing in not being able to decrypt in PHP data that was encrypted in .NET is that in the PHP version you're performing a substr on the ciphertext prior to decryption. The comments in the code indicate that you're removing the IV, except that that seems to have only been relevant in a prior version of your code when you were (correctly) using a random IV each time - now you're just discarding the first 16 bytes of ciphertext which due to the mode of operation corrupts the subsequent data block.
The other problem (though masked by the fact that you're discarding the first 16 bytes of the plaintext data when decrypting in .NET) is that the IV you're using in .NET (16 bytes of 0x00) is not the same as the IV you're using in PHP (16 '0' characters = 16 bytes of 0x30).
I would suggest reverting to using a random IV for every encryption and prepending the IV to the ciphertext after encryption When decrypting, read the IV from the first bytes of the ciphertext then decrypt the remainder. This is much more secure than having a static IV, especially when the data being encrypted is likely to often be the same.
It looks like it's a simple character encoding issue. Your C# code is getting the ASCII representation of your string and encrypting that, but your PHP code is decrypting it and expecting it to be UTF-8.
Try swapping your Encoding.ASCII calls for Encoding.UTF8 and make sure your crypt.Charset and crypt.SetEncodedIV are UTF8 as well
I'm trying to write a service to SFTP to a server on a given interval, download all files in a directory, and then decrypt them for processing.
The decrypt method was working at one point, and I have no modified it since. I am still using the same keys as when it did successfully work.
I am using the PGPEncrypt, PGPDecrypt, and PGPEncryptionKeys classes for BouncyCastle found here: https://github.com/sledwith/PGP-Decryption-With-C-Sharp
Additionally, I have modified the code as shown here: Exception on decrypting file using BouncyCastle PGP
If you noticed, I commented on how that fixed my code and the decryption worked.
Now, it isn't.
Does anyone have some insight why this might have happened, or how I could go about fixing it?
I am going to make a guess that you are using a 1024 bit RSA public/private key and trying to encrypt 128 bytes of something with it? If I am right, use a larger RSA key (RSA 4096 will allow you to encrypt up to ~500 bytes).
I note in the linked post you say this is sporadic. Some googling indicates that if you have leading zeros in the to-be-encrypted bytes it may be able to handle a full 128 bytes.
Also - if you are just encrypting "data" with the keypair, you need to be certain it will not overrun these limitations (240 or so bytes for RSA 2048 and 500 or so for RSA 4096 accounting for padding). Good practice and future proofing would be to implement a symmetric key encryption of all your data and just use the RSA key to encrypt / decrypt your keys.
If you're not dead-set on using the PGP process explicitly, you might use my library here:
https://github.com/zenith-nz/ObscurCore
Its "banner feature" is not yet fully active (creating encrypted archives of a kind), but it does everything that you want it for, it appears - it does key derivation with a ECDHC scheme, UM1, and implements a large variety of block and stream ciphers. It's built on top of BouncyCastle.
I think I resolved this problem; please try this code.
public string StringToDecrypt(string text)
{
byte[] toDecrypt = Convert.FromBase64String(text);
AsymmetricCipherKeyPair keyPair;
using (var reader = File.OpenText(#"Private Key File Path"))
{
keyPair = (AsymmetricCipherKeyPair) new PemReader(reader).ReadObject();
}
var engine = new RsaEngine();
engine.Init(false, keyPair.Private);
return Encoding.UTF8.GetString(engine.ProcessBlock(toDecrypt, 0, toDecrypt.Length));
}
I have an Encyption Part in my C# program that is encrypted with DES encryption. It just encrypts "005". I want this part but with RSA encryption.I don't know how to use C# codes.Can anyone help me
/*********************Message Encryption******************************/
string smsg = "005";
string venc;
DESCryptoServiceProvider iDESCryptoServiceProvider = new DESCryptoServiceProvider();
System.Text.Encoding iEncoding = new System.Text.UTF8Encoding();
byte[] vkey = iEncoding.GetBytes("12345678");
byte[] viv = { 1, 2, 3, 4, 5, 6, 7, 8 };
ICryptoTransform iICryptoTransform = iDESCryptoServiceProvider.CreateEncryptor(vkey, viv);
byte[] vmsg = iEncoding.GetBytes(smsg);
byte[] benc = iICryptoTransform.TransformFinalBlock(vmsg, 0, vmsg.Length);
venc = System.Convert.ToBase64String(benc);
/****************Message Encryption******************************/
This is more of a cryptography task.
Anyway, what you need to do is to swap DESCryptoServiceProvider for RSACryptoServiceProvider. Additionally, as RSA is a PKI cipher while DES is a symmetric block cipher, you will need to create appropriate parameters and so on. So the actual encryption will be also done using different keys, if that was one of your goals to achieve.
Finally, all the necessary code can be found at
http://msdn.microsoft.com/en-us/library/system.security.cryptography.rsacryptoserviceprovider.aspx
EDIT
Ok, so from what I gather from your responses, You don't actually want to use RSA. Just any other cipher, right?
In that case, what you can choose from, assuming you want to keep .NET' System.Security.Crytography library as your source, you can choose from 4 symmetric encryption (read the same type of) algorithms. These are:
AES
DES
RC2
TripleDES
They have all very similar interface, so just choose one of them (my advice is to pick AES) and rework your code. They have identical interfaces (if I didn't miss something from the quick look), so all you would really need to do is to replace all occurrences of DES with AES. As simple as that.
Hope this helps.