How to calculate HMAC-SHA1 authentication code in .NET 4.5 Core

Question

I’m currently facing a big problem (Environment: .NET 4.5 Core): We need to protect a message with a key using a HMAC-SHA1 algorithm. The problem is that the HMACSHA1-class of the namespace System.Security.Cryptography and the namespace itself do not exist in .NET 4.5 Core, this namespace only exists in the normal version of .NET.

I tried a lot of ways to find an equivalent namespace for our purpose but the only thing I found was Windows.Security.Cryptography which sadly does not offer a HMAC-Encryption.

Does anyone have an idea how I could solve our problem or is there any free to use 3rd-party solution?

Angloindian

For clarification, when you refer to .net 4.5 core, you are meaning the win8 api subset of .net 4.5, which is why you don't have access to System.Security.Cryptography? – Germany

Answer 1

The Windows.Security.Cryptography namespace does contain HMAC.

You create a MacAlgorithmProvider object by calling the static OpenAlgorithm method and specifying one of the following algorithm names: HMAC_MD5 HMAC_SHA1 HMAC_SHA256 HMAC_SHA384 HMAC_SHA512 AES_CMAC

http://msdn.microsoft.com/en-us/library/windows/apps/windows.security.cryptography.core.macalgorithmprovider.aspx

public static byte[] HmacSha1Sign(byte[] keyBytes, string message){ 
    var messageBytes= Encoding.UTF8.GetBytes(message);
    MacAlgorithmProvider objMacProv = MacAlgorithmProvider.OpenAlgorithm("HMAC_SHA1");
    CryptographicKey hmacKey = objMacProv.CreateKey(keyBytes.AsBuffer());
    IBuffer buffHMAC = CryptographicEngine.Sign(hmacKey, messageBytes.AsBuffer());
    return buffHMAC.ToArray();

}

Germany

Thank you for your quick response. This was helpful I was able to run the CreateHMAC method (described on technet msdn.microsoft.com/en-us/library/windows/apps/xaml/…) successfuly but what I need is something like this: HMAC_SHA1("key", "The quick brown fox jumps over the lazy dog") = 0xde7c9b85b8b78aa6bc8a7a36f70a90701c9db4d9 Do you know how I can retrieve such a hash-value. Thank you in advance – Angloindian