CODEWITHSUNDEEP
c#
Get Off My Lawn
Get Off My Lawn

Reputation: 36311

Sha256 is creating wrong hash

I am trying to calculate a sha256, and this code seems to be doing it wrong.

private static string GetSHA256(string text){
    UnicodeEncoding UE = new UnicodeEncoding();
    byte[] hashValue;
    byte[] message = UE.GetBytes(text);

    SHA256Managed hashString = new SHA256Managed();
    string hex = "";

    hashValue = hashString.ComputeHash(message);
    foreach (byte x in hashValue){
        hex += string.Format("{0:x2}", x);
    }
    return hex;
}

I have a server that generates a sha256 based on data sent to it, and the the value from this sha256 doesn't match the one on the server. I have tried generating the same using PHP, and JavaScript, and those both generate the same sha256 as the server, so I have come to the conclusion that this has to be what is wrong.

with php I am using this:

$time = time();
$str = "5550d868c5242fb3299a2604|$time|1431619392-36e2d4f3b5de0bfd5f26e3efabbbd99dc2503dab";

$hash = hash("sha256", $str);

Here is what is getting hashed with C#

string time = ((DateTime.UtcNow - new DateTime(1970, 1, 1, 0, 0, 0, 0)).TotalSeconds).ToString();
GetSHA256("5550d868c5242fb3299a2604|"+time+"|1431619392-36e2d4f3b5de0bfd5f26e3efabbbd99dc2503dab")

As you can see they are both the same format, so I think that this is the issue. Can anyone see how I am hashing differently in C#?

Upvotes: 1

Views: 1700

Answers (1)

Tim S.
Tim S.

Reputation: 56536

UnicodeEncoding uses UTF-16 encoding. Your encoding should match what PHP uses, which is probably either UTF-8 or ASCII (which are equivalent if you only use the common, simple characters used in your example).

private static string GetSHA256(string text){
    byte[] message = Encoding.UTF8.GetBytes(text);

    SHA256Managed hashString = new SHA256Managed();

    byte[] hashValue = hashString.ComputeHash(message);
    string hex = "";
    foreach (var x in hashValue){
        hex += string.Format("{0:x2}", x);
    }
    return hex;
}

Upvotes: 4

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