Converting a md5 hash byte array to a string

Question

How can I convert the hashed result, which is a byte array, to a string?

byte[] bytePassword = Encoding.UTF8.GetBytes(password);

using (MD5 md5 = MD5.Create())
{
    byte[] byteHashedPassword = md5.ComputeHash(bytePassword);
}

I need to convert byteHashedPassword to a string.

MD5 is deprecated. It is inherently broken as it does not reach the standards of collision or preimage resistance. For passwords, it's better to use iterated key-derivation functions such as Argon2 or PDKDF2. — Kerrmiter, Apr 16 '21 at 07:54

score 89 · Accepted Answer · answered Mar 12 '10 at 20:40

89

   public static string ToHex(this byte[] bytes, bool upperCase)
    {
        StringBuilder result = new StringBuilder(bytes.Length*2);

        for (int i = 0; i < bytes.Length; i++)
            result.Append(bytes[i].ToString(upperCase ? "X2" : "x2"));

        return result.ToString();
    }

You can then call it as an extension method:

string hexString = byteArray.ToHex(false);

answered Mar 12 '10 at 20:40

Philippe Leybaert

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what is the significance of upper casing? – Blankman Mar 12 '10 at 20:41
3

a matter of preference. That's why I added a parameter to my method, so the caller can choose – Philippe Leybaert Mar 12 '10 at 20:42
It's the difference between `c0de` and `C0DE`, that's all. – John Kugelman Mar 12 '10 at 20:43
13

No need to reinvent the wheel when you already have `Convert.ToBase64String()` – Eric Petroelje Mar 12 '10 at 20:46
oh ok, I thought there was more too it! how does your answer differ from Convert.ToBase64String(bytes)? – Blankman Mar 12 '10 at 20:46
6

A Base64 string is shorter. It uses all letters of the alphabet, digits and a few punctuation characters, so it's not hexadecimal. Base64 uses 4 characters for 3 bytes, while a hex string uses 6 characters for 3 bytes. – Philippe Leybaert Mar 12 '10 at 20:49
7

@Eric: there are situations where Base64 is not a good choice because of the extra punctuation characters that are used (passing it in a URL for example) – Philippe Leybaert Mar 12 '10 at 20:50

score 70 · Answer 2 · answered Mar 12 '10 at 20:49

I always found this to be the most convenient:

string hashPassword = BitConverter.ToString(byteHashedPassword).Replace("-","");

For some odd reason BitConverter likes to put dashes between bytes, so the replace just removes them.

Update: If you prefer "lowercase" hex, just do a .ToLower() and boom.

Do note that if you are doing this as a tight loop and many ops this could be expensive since there are at least two implicit string casts and resizes going on.

does the same as @PhilippeLeybaert solution, but in one-line. — sonjz, Jul 03 '13 at 20:05

score 31 · Answer 3 · answered Mar 12 '10 at 20:40

31

You can use Convert.ToBase64String and Convert.FromBase64String to easily convert byte arrays into strings.

answered Mar 12 '10 at 20:40

David

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score 23 · Answer 4 · answered Dec 22 '13 at 01:57

23

If you're in the 'Hex preference' camp you can do this. This is basically a minimal version of the answer by Philippe Leybaert.

string.Concat(hash.Select(x => x.ToString("X2")))

B1DB2CC0BAEE67EA47CFAEDBF2D747DF

answered Dec 22 '13 at 01:57

Simon_Weaver

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score 10 · Answer 5 · answered Mar 12 '10 at 20:41

Well as it is a hash, it has possibly values that cannot be shown in a normal string, so the best bet is to convert it to Base64 encoded string.

string s = Convert.ToBase64String(bytes);

and use

byte[] bytes = Convert.FromBase64(s);

to get the bytes back.

score 7 · Answer 6 · answered Mar 12 '10 at 20:42

Well, you could use the string constructor that takes bytes and an encoding, but you'll likely get a difficult to manage string out of that since it could contain lots of fun characters (null bytes, newlines, control chars, etc)

The best way to do this would be to encode it with base 64 to get a nice string that's easy to work with:

string s = Convert.ToBase64String(bytes);

And to go from that string back to a byte array:

byte[] bytes = Convert.FromBase64String(s);

score 1 · Answer 7 · answered Nov 08 '22 at 19:49

1

I know this is an old question, but I thought I would add you can use the built-in methods (I'm using .NET 6.0):

Convert.ToBase64String(hashBytes); (Others have already mentioned this)
Convert.ToHexString(hashBytes);

answered Nov 08 '22 at 19:49

Dazfl

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score 0 · Answer 8 · answered May 30 '15 at 00:21

For anyone interested a Nuget package I created called CryptoStringify allows you to convert a string to a hashed string using a nice clean syntax, without having to play around with byte arrays:

using (MD5 md5 = MD5.Create())
{
    string strHashedPassword = md5.Hash(password);
}

It's an extension method on HashAlgorithm and KeyedHashAlgorithm so works on SHA1, HMACSHA1, SHA256 etc too.

https://www.nuget.org/packages/cryptostringify

Converting a md5 hash byte array to a string

8 Answers8

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