Background 🧐
Today I was looking to generate SHA256 hash for input string data. Below are my notes on how I used dotnet script (interactive scripting experience) in .NET to experiment with it.
P.S. - Writing these small .NET recipes helps me in absorbing more.
Walkthrough ⚡
Using dotnet script
To quickly test features in .NET core, I use the dotnet script global tool.
Begin with creating a dotnet script file (.csx extension).
mkdir hashing
cd hashing
dotnet script init sha256hash
Above dotnet command creates an executable file with below content.
#!/usr/bin/env dotnet-script
Console.WriteLine("Hello world!");
Since this is an executable script, we can run it like this as well.
./sha256hash.csx
Output:
Hello world!
Using statements in scripts
Now, let’s modify this script to explore creating a SHA256 hash.
First, thing is we need to place some using statements to bring in the Cryptography and Text namespace like below.
So the content now looks like.
#!/usr/bin/env dotnet-script
// Add the using statements
using System.Text;
using System.Security.Cryptography;
Reading the docs
Moving on, after browsing the documentation of the SHA256 class I noticed a Create() method which creates a default instance.
Also, noticed that the inheritance chain for this class is Object -> HashAlgorithm -> SHA256
HashAlgorithm is the base class with below signature, notice it in turn inherits from IDisposable interface this immediately reminded me to use the using statement syntax to conveniently dispose this object after re-use, rather than calling Dispose() method myself inside try/catch/finally statements.
public abstract class HashAlgorithm : IDisposable, System.Security.Cryptography.ICryptoTransform
#!/usr/bin/env dotnet-script
using System.Text;
using System.Security.Cryptography;
string text = "DexterPOSH"; // this is our text for which we will generate hash
using (SHA256 hashAlgorithm = SHA256.Create())
{
// place holder
};
The docs also reveal the ComputeHash() method which takes byte[] array as argument and returns the byte array back as well.
We need some way to convert our string input to byte array.
string to byte[] conversion
Quick search suggests to use Encoding.UTF8.GetBytes() static method for converting string to byte array.
Using that in code now leads us to this point.
#!/usr/bin/env dotnet-script
using System.Text;
using System.Security.Cryptography;
string text = "DexterPOSH"; // this is our text for which we will generate hash
using (SHA256 hashAlgorithm = SHA256.Create())
{
var hashedByteArray = hashAlgorithm.ComputeHash(Encoding.UTF8.GetBytes(input));
Console.WriteLine(hashedByteArray);
}
Output:
System.Byte[]
Let’s see how we can convert the byte[] to string object.
byte[] to string conversion
Again search and got a hint of using the BitConverter.ToString() static method.
Let’s add that logic in our script.
#!/usr/bin/env dotnet-script
using System.Text;
using System.Security.Cryptography;
string text = "DexterPOSH"; // this is our text for which we will generate hash
using (SHA256 hashAlgorithm = SHA256.Create())
{
var hashedByteArray = hashAlgorithm.ComputeHash(Encoding.UTF8.GetBytes(input));
Console.WriteLine(BitConverter.ToString(hashedByteArray));
};
Output:
1C-29-A2-30-0A-8A-99-6F-67-60-70-7E-21-0D-BD-61-B1-C9-3A-B7-4F-86-EE-13-7B-2E-DE-B6-01-6E-87-93
remove ‘-’ from string
As the last step let’s replace the char - from the output string.
String class has replace method which invoke.
#!/usr/bin/env dotnet-script
using System.Text;
using System.Security.Cryptography;
using (SHA256 hashAlgorithm = SHA256.Create())
{
string input = "DexterPOSH";
byte[] data = hashAlgorithm.ComputeHash(
Encoding.UTF8.GetBytes(input)
);
Console.WriteLine(BitConverter.ToString(data).Replace("-", String.Empty));
}
Output:
1C29A2300A8A996F6760707E210DBD61B1C93AB74F86EE137B2EDEB6016E8793
Solution 😎
Content of the sha256hash.csx file.
#!/usr/bin/env dotnet-script
using System.Text;
using System.Security.Cryptography;
using (SHA256 hashAlgorithm = SHA256.Create())
{
string input = "DexterPOSH";
byte[] data = hashAlgorithm.ComputeHash(
Encoding.UTF8.GetBytes(input)
);
Console.WriteLine(BitConverter.ToString(data).Replace("-", String.Empty));
}
Run the above file
dotnet script run ./sha256hash.csx # or simply ./sha256hash.csx
Output:
1C29A2300A8A996F6760707E210DBD61B1C93AB74F86EE137B2EDEB6016E8793
Reference links 📖
System.Security.CryptoGraphy Class