Encrypting in Unity, decrypting in Node.js

Question

I am trying to send some data from Unity to Node.js express server and vice versa.

Here is my Unity code in C#:

public string Encrypt(string toEncrypt, string key, bool useHashing) 
{     

    byte[] keyArray;     
    byte[] toEncryptArray = UTF8Encoding.UTF8.GetBytes(toEncrypt);      

    if (useHashing){               
        MD5CryptoServiceProvider hashmd5 = new MD5CryptoServiceProvider();
        keyArray = hashmd5.ComputeHash(UTF8Encoding.UTF8.GetBytes(key));     
    }     
    else {
        keyArray = UTF8Encoding.UTF8.GetBytes(key);      
    }

    var tdes = new TripleDESCryptoServiceProvider();
    tdes.Key = keyArray;
    //tdes.Mode = CipherMode.CBC;  // which is default     
    //tdes.Padding = PaddingMode.PKCS7;  // which is default

    ICryptoTransform cTransform = tdes.CreateEncryptor();     
    byte[] resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);
    tdes.Clear();
    return Convert.ToBase64String(resultArray, 0, resultArray.Length); 

}

    Dictionary<string, string> data = new Dictionary<string, string>();
    data.Add("Test01", "Tanmoy");
    data.Add("Test02", "Mitra");
    string json = Json.Serialize(data);

    byte[] postData = Encoding.UTF8.GetBytes(Encrypt(json, "12345", true));

    StartCoroutine(HttpPost("test", postData, delegate(string requestError, IDictionary rData) {
        cb(null,rData);
    }));

And here is my Node.js code:

var alg = 'des-ede3-cbc';
var key = new Buffer('123456789012345678901234', 'utf-8');
var iv = new Buffer(m_strApiPass, 'base64');

var encrypted = new Buffer(reqString, 'base64');

var decipher = crypto.createDecipheriv(alg, key, iv);
var decoded = decipher.update(encrypted, 'binary', 'ascii');
decoded += decipher.final('ascii');

I am getting this error:

TypeError: error:0606506D:digital envelope routines:EVP_DecryptFinal_ex:wrong final block length

What I have noticed, in C#, I got following string,

pySqIdAiJpDOW7XkOQDoblLOtZ382J1G1F1UE16W0Ulg+x5X0Bocjg==

but when I send this string to Node.js, it becomes:

pySqIdAiJpDOW7XkOQDoblLOtZ382J1G1F1UE16W0Ulg x5X0Bocjg

What could the issue be?

Doesn't have to do much with Unity3D in itself I guess. It's good that you document the defaults, but I would just set them. It is unlikely to cost you any performance, and relying on defaults in crypto is a dangerous game. Don't forget to add a MAC as this is vulnerable to padding oracle attacks. — Maarten Bodewes
– Maarten Bodewes, Commented Jan 21, 2014 at 11:57

Maarten Bodewes · Accepted Answer · 2014-01-21 11:55:58Z

2

The reason is simple: the returned ciphertext consists of random looking bytes to any observer. This means that there are bytes in there which do not map to a character. The information within those bytes is lost.

If you require a string during transmission, base 64 encode your ciphertext instead, and decode it again at the receiving side.

answered Jan 21, 2014 at 11:55

Maarten Bodewes

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