Generate a Guid based on a string

Question

We would like to generate a Guid based on some random string. The goal would be that the Guid is always the same for a given string.

Just to be clear, my string is not formated as a guid, it could be "Toto" as "asdfblkajsdflknasldknalkvkndlskfj".

I know that this would generate some Guid that is as unique as my input string, but it's not the question here.

I think you want to hash a guid maybe?however this in itself doesn't really make much sense — TheGeneral, Apr 03 '18 at 10:54
I think it does not really make sense to use a Guid then - it would make more sense to use any hashing function. Why exactly do you think you need a Guid? — Larce, Apr 03 '18 at 10:55
You can take a look at this answer for ideas: https://stackoverflow.com/a/6248764/9583065 — Timovski, Apr 03 '18 at 10:57

score 9 · Answer 1 · answered Apr 03 '18 at 10:56

9

Since both a Guid and a MD5 hash are 128 bits integers, you could use the MD5 of a given string as the Guid. It will reproduce the same value consistently:

using (System.Security.Cryptography.MD5 md5 = System.Security.Cryptography.MD5.Create())
{
    byte[] inputBytes = System.Text.Encoding.ASCII.GetBytes(input);
    byte[] hashBytes = md5.ComputeHash(inputBytes);

    Guid g = new Guid(hashBytes);
}

answered Apr 03 '18 at 10:56

Patrick Hofman

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This works practically. However, not that you violate the policy of a Guid, so theoretically it does not make sense to use a Guid here at all - I would just go for a simple String of the new hash. Of course you can then format it as you like and make it look like a Guid - even if it isn't theoretically. – Larce Apr 03 '18 at 11:00
Anyway I wouldn't use MD5 anymore. If input distribution is as good as original Guid distribution MD5 algorithm may increase the likelihood of collisions. – arekzyla Apr 03 '18 at 11:24
A valid argument to not do what OP asks @arekzyla. – Patrick Hofman Apr 03 '18 at 11:25

Generate a Guid based on a string

1 Answers1