Hashing with SHA1 Algorithm in C#

Question

I want to hash given byte[] array with using SHA1 Algorithm with the use of SHA1Managed.
The byte[] hash will come from unit test.
Expected hash is 0d71ee4472658cd5874c5578410a9d8611fc9aef (case sensitive).

How can I achieve this?

public string Hash(byte [] temp)
{
    using (SHA1Managed sha1 = new SHA1Managed())
    {

    }
}

Your excpected hash is a hexadecimal value, so it doesnt matter if it's case sensitive e.g. hex(e) == hex(E) — jAC
– jAC, Commented Jun 25, 2013 at 8:24

Mitch · Accepted Answer · 2024-03-14 16:09:28Z

226

For those who want a "standard" text formatting of the hash, you can use something like the following for .NET 5 and newer:

static string Hash(string input)
    => Convert.ToHexString(SHA1.HashData(Encoding.UTF8.GetBytes(input)));

This will produce a hash like 0C2E99D0949684278C30B9369B82638E1CEAD415.

If you are stuck on pre-.NET 5 where Convert.ToHexString is not available, you can do:

static string Hash(string input)
{
    using (SHA1Managed sha1 = new SHA1Managed())
    {
        var hash = sha1.ComputeHash(Encoding.UTF8.GetBytes(input));
        var sb = new StringBuilder(hash.Length * 2);

        foreach (byte b in hash)
        {
            // can be "x2" if you want lowercase
            sb.Append(b.ToString("X2"));
        }

        return sb.ToString();
    }
}

Or for a code golfed .Net Framework version:

static string Hash(string input)
{
    var hash = new SHA1Managed().ComputeHash(Encoding.UTF8.GetBytes(input));
    return string.Concat(hash.Select(b => b.ToString("x2")));
}

edited Mar 14, 2024 at 16:09

answered Oct 25, 2014 at 0:26

Mitch

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12 Comments

sky-dev Over a year ago

It bugs me that this solution doesn't dispose the SHA1Managed object, because it is marked as Disposable. This post could be handy when optimizing: stackoverflow.com/a/624379/991863

unenthusiasticuser Over a year ago

@Mitch If it implements the IDisposable interface then what happens in the reference source shouldn't matter. Should they ever change it for any reason such that the .Dispose() call becomes important, your previously working code is now causing a problem. Relying on looking into the bowels of a framework to determine what you can get away with is a path to a maintenance nightmare. I highly suggest following the documentation and correctly handling disposable objects, it'll save you pain in the long term.

Mitch Over a year ago

@unenthusiastic use, Haha, thanks. I wasn't sure what the purpose of documentation was... (The code in my production applications is the one from the top, but the circumstances of the second make me comfortable enough that it would be equally supportable in all but the tightest loops. IDisposable is semi-optional when dealing with non-side-effecting classes.)

ijt Over a year ago

What is the "X2" for?

Mitch Over a year ago

@ijt, X2 tells it to use two hexadecimal digits per byte. x2 means lowercase, X2 is uppercase

|

John Gathogo · Accepted Answer · 2013-06-25 08:44:46Z

41

public string Hash(byte [] temp)
{
    using (SHA1Managed sha1 = new SHA1Managed())
    {
        var hash = sha1.ComputeHash(temp);
        return Convert.ToBase64String(hash);
    }
}

EDIT:

You could also specify the encoding when converting the byte array to string as follows:

return System.Text.Encoding.UTF8.GetString(hash);

or

return System.Text.Encoding.Unicode.GetString(hash);

edited Jun 25, 2013 at 8:44

answered Jun 25, 2013 at 8:21

John Gathogo

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6 Comments

Joey Over a year ago

If they want a hex string then Base64 is probably the wrong choice.

John Gathogo Over a year ago

@Joey: Against the answer given by GrantThomas, the member indicated that they need to return a string

John Gathogo Over a year ago

@MerveKaya: Perhaps you should explain what you mean by "it didnt work". What does the incoming byte array represent? How did you determine "SHA1Managed"-hashing the incoming byte array should give you 0d71ee4472658cd5874c5578410a9d8611fc9aef as the output?

Merve Kaya Over a year ago

Byte[] hash comes from unit test. In the question they wrote that expected hash is 0d71ee4472658cd5874c5578410a9d8611fc9aef. It comes from unit test

John Gathogo Over a year ago

@MerveKaya: See my update on how to use Encoding when converting the hash to a string

|

Community · Accepted Answer · 2017-05-23 12:26:35Z

19

This is what I went with. For those of you who want to optimize, check out https://stackoverflow.com/a/624379/991863.

    public static string Hash(string stringToHash)
    {
        using (var sha1 = new SHA1Managed())
        {
            return BitConverter.ToString(sha1.ComputeHash(Encoding.UTF8.GetBytes(stringToHash)));
        }
    }

edited May 23, 2017 at 12:26

CommunityBot

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answered Dec 21, 2015 at 16:38

sky-dev

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1 Comment

Sam Over a year ago

I had to use BitConverter.ToString(sha1.ComputeHash(bytes)).Replace("-", "") since I didn't want the dashes introduced by BitConverter. After that it worked like a charm! Thanks!

Grant Thomas · Accepted Answer · 2013-06-25 08:18:36Z

9

You can "compute the value for the specified byte array" using ComputeHash:

var hash = sha1.ComputeHash(temp);

If you want to analyse the result in string representation, then you will need to format the bytes using the {0:X2} format specifier.

answered Jun 25, 2013 at 8:18

Grant Thomas

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Comments

alireza amini · Accepted Answer · 2016-08-14 14:22:22Z

9

Fastest way is this :

    public static string GetHash(string input)
    {
        return string.Join("", (new SHA1Managed().ComputeHash(Encoding.UTF8.GetBytes(input))).Select(x => x.ToString("X2")).ToArray());
    }

For Small character output use x2 in replace of of X2

answered Aug 14, 2016 at 14:22

alireza amini

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3 Comments

rickythefox Over a year ago

SHA1Managed implements IDisposable, so you would probably want to dispose it when done with it to free up resources.

quetzalcoatl Over a year ago

It's not the fastest way, it's merely packed into a single line.

alireza amini Over a year ago

@quetzalcoatl well, yeah :)

oPless · Accepted Answer · 2015-06-19 00:09:11Z

4

I'll throw my hat in here:

(as part of a static class, as this snippet is two extensions)

//hex encoding of the hash, in uppercase.
public static string Sha1Hash (this string str)
{
    byte[] data = UTF8Encoding.UTF8.GetBytes (str);
    data = data.Sha1Hash ();
    return BitConverter.ToString (data).Replace ("-", "");
}
// Do the actual hashing
public static byte[] Sha1Hash (this byte[] data)
{
    using (SHA1Managed sha1 = new SHA1Managed ()) {
    return sha1.ComputeHash (data);
}

edited Jun 19, 2015 at 0:09

answered Jun 18, 2015 at 23:02

oPless

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